Woodworking Tip of the Day: Flattening Your Sharpening Stones: Pencil Grid, Lapping Plate and How Often

Not for nuthin'…. But….. the sharpest-looking set of stones in a lot of shops is also the reason the chisels won't pare a clean shaving. Waterstones wear every time you use them, and they wear the most right in the middle. Nobody notices until the plane iron comes off the stone with a rounded edge and a back that won't lap flat. I've got a dory's worth of bevels, gains and frames to cut this winter, so I went back to the stone makers' own instructions and the Fine Woodworking and Popular Woodworking articles and wrote down how I keep mine flat.

Why it matters: A waterstone cuts fast because its binder lets go and keeps exposing fresh abrasive. The price is that it dishes. Shapton says it plainly: the blade hits the middle of the stone more often, so the stone goes concave, and that makes for uneven sharpening. Tom Caspar wrote in Popular Woodworking that the wear "produces an undesirable curved edge on chisels and plane irons." It's worse on the back of a blade. Lay a flat back on a hollow stone and it only touches the high ends, so lapping it there rounds it over instead of flattening it. Paul Sellers' answer to that problem is to lap backs on something that stays flat, like a diamond plate or thick glass. A sharp edge is where two faces meet, and a dished stone spoils both of them.

Oilstones vs. waterstones: Norton says its oilstones (benchstones) "typically do not require flattening with normal use" because they're hard, but after years of steady use they can dish in the spots where you bear down the most. Waterstones are the other way around: they dish easily, but they're quick to bring back. Same job, different schedule.

Materials

• Your sharpening stones, every grit (not just the coarse one)
• A soft pencil
• Water, plus a tub or a sink without a garbage disposal (DMT says the slurry is hard on disposal bearings)
• Rags and a stiff nylon brush for cleanup

Tools: pick one flattener

• Diamond lapping plate. The DMT Dia-Flat (DMT is out of Marlborough, Mass.) is 10" × 4", ground flat to ±0.0005", and comes in 120 micron for stones of 1000 grit and coarser or 95 micron for finer stones. An Atoma plate is 140x or 400x diamond on a 10 mm aluminum block, flat to ±0.04 mm (about 0.0016"). Lee Valley suggests the 400x for general truing and the 140x when you need to take off a lot fast.
• Coarse diamond stone. Lee Valley says a coarse (about 400x) metal-backed diamond plate makes a good flattener and doubles for grinding a primary bevel. There's a catch, though. DMT doesn't recommend its regular sharpening plates for lapping stones, only the ones marked Dia-Flat, and Deneb Puchalski (Fine Woodworking) warns that some diamond stones wear out of flat fast. If you use one, keep it just for lapping.
• Silicon carbide grit on glass. Lee Valley's lapping kit says to true stones with 90x or 180x and finish with 280x, on plate glass, with water as the only lubricant for waterstones. Their guide calls for glass at least 1/4" thick, supported on flat plywood or MDF so it can't flex. A plastic laminate sheet on the glass keeps the grit from dishing the glass itself. (Don't use loose grit on a steel plate for waterstones. Lee Valley says the oxides from a wet ferrous lap will ruin the stone.)
• Wet/dry sandpaper on glass or granite. It's the cheapest way in. Norton says 100 grit, Charlesworth used 180 or 240 on 1/2" float glass, and Caspar used 220 on plate glass 1/4" or thicker. Lee Valley also lists coarse aluminum oxide sheet (over 100 micron) on glass or granite. Sellers' advice for a flat granite tile is to take a straightedge to the store and pick through them until you find a flat one.
• Grooved silicon carbide flattening stone. Norton recommends one. Soak it and the waterstone, then rub them together, and the grooves carry the slurry away.
• Shapton's Diamond Glass Lapping Plate is only for stones of 500 grit (30 micron) and finer. Don't use it on coarse stones, don't put loose grit on it and don't run hot water over it.
• A good straightedge

Steps

1. Wet everything. Soak your soaking stones the way the maker says. Shapton says to give its stones 2 to 3 minutes before lapping and to let other brands soak up all the water they can hold. Set the plate or glass on something solid and flat, and splash it with water.
2. Draw a pencil grid across the whole face of the stone. Fine Woodworking, Lee Valley and Shapton all start this way. The pencil shows you what the stone is doing.
3. Lap with long figure-8 strokes. DMT says to use long, overlapping figure-8s with light to moderate pressure and the whole plate, and to finish lighter so you leave fewer scratches. Shapton's way, forward and back and then both diagonals, works just as well. Turn the stone end for end now and then. Keep it wet, and rinse the slurry out of the plate's grooves as it builds up.
4. Read the grid. The lines go first on the high spots. On a dished stone that's the ends and edges, and the middle hangs onto its lines the longest. When every line is gone, the stone is flat. Lee Valley says not to fuss if it doesn't quite reach the corners, since that's the part of the stone that matters least.
5. Check it with a straightedge. Lay it along the length, the width and both diagonals and hold the stone up to the light. If any light shows under it, go back to the plate.
6. Chamfer the edges. Caspar sands a 45° bevel on every edge of the stone "to prevent flaking." Charlesworth eased the soft edges so they wouldn't crumble. Touch them up after each flattening, since lapping leaves a sharp corner again.
7. Do every stone. The 1000, the 4000 and the 8000 all wear, just at different rates. Rinse and brush each stone before you go to the next grit so coarse grit doesn't ride along and scratch up your finish stone. If you'd rather lap stone against stone, use three and keep rotating them. Lee Valley warns that rubbing just two together can leave one concave and the other convex.
8. Clean up the flattener. DMT says to clean and dry the Dia-Flat after every use, and to scrub any diamond plate now and then with a nylon brush and a mild cleanser. Lee Valley says to wipe the swarf out of an Atoma's channels. Put a straightedge across your plate or glass once in a while too, because a flattener that isn't flat just copies its own error into every stone.

How often? More often than you'd think. Lee Valley says to lap waterstones every 3 to 5 minutes of use. Shapton says to lap every time you sharpen a blade. Charlesworth flattened his 800 after about 100 strokes of back work, and Caspar flattened his three stones before every session, which he said took a minute or so. Plenty of folks flatten at the end of each session so the stones are ready the next time. Oilstones are on a much longer clock: check them with the straightedge now and then and flatten when they show a dish. The rule is little and often. A stone that's barely off comes back in a minute, and a badly dished one costs you a lot of stone.

One for the New England shop: Charlesworth warns not to store waterstones in water if the shop freezes at night, "because the stones will shatter." Come December in an unheated Marblehead shop, my soakers come in the house or get stored dry.

MOAM's shop note: The mistake I see most is flattening the 1000 and calling it done. The finish stone dishes too, just slower, and it's the last stone that touches your edge. The second most common is the fella who flattens only when he can see the hollow. By the time you can see it, you've already rounded a few irons. Draw the grid, lap it out, knock off the edges, and keep your flattener clean and flat. A few minutes, and every stone on the bench is flat.

Sources: DMT Dia-Flat product page and DMT FAQ, Lee Valley's Atoma Diamond Plates page, Lapping Grits instructions, "Getting Started with Japanese Water Stones," "Care and Maintenance of Ceramic and Water Stones" and Sharpening by Hand guide, Shapton Diamond Glass Lapping Plate instructions and FAQ, Norton "A Guide to Waterstones" and "A Guide to Benchstones," David Charlesworth, "A User's Guide to Waterstones" (Fine Woodworking #169), Deneb Puchalski, "Flatten Waterstones with a Coarse Diamond Stone" (Fine Woodworking #224), Hendrik Varju, "Pencil and Paper" (Fine Woodworking), Tom Caspar, "Waterstones" (Popular Woodworking / American Woodworker), and Paul Sellers, "Sharpening on hollow stones."

MOAM Out.

Woodworking Tip of the Day: Oil Finishes: Linseed, Tung or Danish Oil, and Disposing of Oily Rags Safely

Not for nuthin'…. But….. it's Halloween, and the scariest thing in most shops tonight isn't a costume. It's a wad of oily rags balled up in the trash barrel in the corner. Before we get to that, let's straighten out what's actually in those cans of "linseed," "tung" and "Danish" oil, because the labels sure won't tell you. I've got thwarts, a tiller and a rack of tool handles waiting on the dory, so I went back to the makers' own directions and Bob Flexner's finishing work and wrote it all down.

Why it matters: An oil finish is about the easiest finish there is: wipe it on, wipe it off, and it brings the grain up warm. But it only cures right if you take off every bit of the excess, and every rag you used is a fire waiting to happen until you deal with it. NFPA counts an average of about 900 home fires a year started by oily rags.

What's really in the can

• Raw linseed oil is straight flax oil with no driers. It takes weeks to cure. Flexner says he knows of no interior use for it, and I'd leave it on the shelf for furniture and trim.
• Boiled linseed oil (BLO) isn't boiled. It's linseed oil with metallic driers, so it cures in about a day once the excess is off. Klean-Strip says to let it soak in 10 minutes, wipe off all the surface film, and figure up to 16 hours to tack-free and several days to fully cure. Good on tool handles, mallets and shop jigs.
• Pure tung oil gives you the best water resistance you'll get from a straight oil, but it's slow. Waterlox says to thin it about 1:1 for most work, let each coat soak in for up to 45 minutes, and keep re-wetting until it sits on top. Then wipe off all the excess and give it 7 to 14 days to dry and up to 30 days to fully cure. Flexner figures five to seven coats, with two to three days between them and a light sanding after every coat.
• "Danish oil" and most "tung oil finish" products are oil/varnish blends. Flexner lists Watco Danish Oil and Minwax Tung Oil Finish as blends, and some other "tung oil" products (Formby's, for one) as thinned wiping varnish. A blend gives you a little more protection than plain oil and is just as easy to wipe on. One more curveball: Tried & True calls its straight polymerized linseed oil "Danish Oil." Read the ingredients, not the name.

Where oil belongs in a boat shop: interior trim, thwarts and seats on a boat that lives under cover, tool handles, bench tops and cabinets. Oil alone isn't exterior brightwork. It darkens in the sun and needs regular maintenance coats, and Watco, Minwax Tung Oil Finish and Tried & True are all labeled for interior use. For brightwork that lives out in the salt air, oil is a maintenance plan, not a finish. (If you want a film that builds, that's the wiping varnish from the Oct. 19 tip.)

Materials

• Your oil: BLO, pure tung (plus mineral spirits or citrus solvent to thin it), or an oil/varnish blend like Watco Danish Oil
• A pile of clean, lint-free cotton rags (old T-shirts work)
• 0000 steel wool or 220-grit paper for between coats
• An old metal paint can with a tight lid, water and a squirt of dish detergent
• Nitrile gloves

Tools

• Cheap natural-bristle brush or a folded rag for flooding it on
• Random-orbit sander or a sanding block for prep
• A clear spot outdoors, away from the building, plus a few rocks or scrap blocks to weigh rags down

Steps

1. Read the can first. If mineral spirits or petroleum distillate is on the ingredient list, it isn't pure oil. If you're not sure, do Flexner's puddle test: half a teaspoon on a piece of glass, then wait 24 hours to a couple of days. Smooth and hard means wiping varnish. Soft and wrinkled means an oil/varnish blend.
2. Prep bare wood. Get every old finish off, sand smooth (Watco's sheet runs 120, 150, 180, 220), and vacuum or wipe off all the dust. Oil goes on bare wood only, because it has to soak in to cure.
3. Flood it on. Use a brush or rag and lay it on heavy, adding more wherever it soaks right in. End grain will drink it.
4. Let it soak, on the label's clock. Watco Danish Oil: 30 minutes, then wet it again and give it 15 more. Minwax Tung Oil Finish: 5 to 10 minutes. BLO: about 10 minutes. Pure tung: up to 45 minutes, re-wetting the dry spots until the oil just sits there.
5. Wipe off ALL the excess. Use clean, dry rags, with the grain, until the surface feels dry. Then change rags and do it again. Anything you leave on top cures soft and gummy. This is the step that makes or breaks an oil finish.
6. Come back for the bleed-back. Open-grained wood like oak and mahogany pushes oil back out of the pores. Check it over the next hour or so and wipe off any shiny beads. On pure tung, keep a rag handy for the first couple of weeks.
7. Let it cure. Watco says it's ready for light use in 8 to 10 hours. Minwax says 24 hours between coats. BLO, overnight at least. Pure tung takes days. Cold shops are slower, and Watco wants 60 to 90°F.
8. Scuff and recoat. Knock down the raised grain with 0000 steel wool or 220, wipe off the dust, and repeat. Two or three coats of BLO or a blend (Minwax says two), and five to seven for pure tung. Going over it with varnish? Watco says to wait 72 hours first.
9. Deal with the rags right then and there. See below. Not after supper.

The rags. Read this part twice. Linseed and tung oil cure by soaking up oxygen, and that reaction gives off heat. Spread out flat, the heat just drifts away. Wad it up in a pile or a trash bag and the heat builds until the rag lights itself, hours later, after you've shut the lights off and gone in the house. NFPA and the Massachusetts fire officials say:

• Never leave oily rags in a pile, a box or the trash.
• Option A: Hang them or spread them flat outdoors in a single layer, weighed down so they don't blow around, away from buildings, until they're completely dry and stiff. Klean-Strip says at least 24 hours above 40°F for BLO rags, and Waterlox figures 7 to 15 days for pure tung.
• Option B: Put them in a metal can with a tight lid (an old paint can is perfect), cover them completely with water and a little detergent, and keep the can somewhere cool and out of the sun. Watco's safety sheet says to put soaked rags straight into a sealed, water-filled metal container.
• Either way, the can of rags goes to your town's household hazardous waste collection, not the barrel. Check with your town for the date.
• The same goes for steel wool, paper towels, brushes and your shop apron if it got soaked.

MOAM's shop note: The mistake I see most is the "one more coat for good measure" fella who floods it on and walks away. Oil isn't varnish. It doesn't build, and whatever's left on top turns into a sticky, wrinkled mess that you'll be scraping off in a week. Wipe it like you're trying to take it all back off. The wood keeps what it needs.

Sources: Watco Danish Oil technical data sheet and Rust-Oleum safety data sheet, Minwax Tung Oil Finish directions, Klean-Strip boiled linseed oil guidance, Waterlox 100% Pure Tung Oil application guide, Tried & True product directions, Bob Flexner, "Oil Finishes: Their History and Use" (Popular Woodworking), Hendrik Varju, "The Confusion Over Wipe-On Finishes" (Fine Woodworking #207), Power & Motoryacht, "Varnishes, Oils, and a Little Heresy," NFPA "Oily Rags" safety tip sheet, and Mass.gov, "Disposing of oily rags."

MOAM Out.

Woodworking Tip of the Day: Edge-Gluing a Panel: Board Layout, Clamp Spacing and Squeeze-Out

Here's one every shop gets wrong at least once….. you glue up a nice wide panel, pull the clamps the next morning, and it's bowed like a potato chip, or there's a starved seam you can see from across the room. The dory needs a couple of solid-wood panels for the seat tops and a hatch, so I went back to the glue maker's own numbers and Fine Woodworking's clamping advice and wrote down how to do it right the first time.

Why it matters: A good edge joint with today's glues is stronger than the wood around it. But the glue only does its job if the edges meet tight, the pressure is even all along the seam, and the panel stays flat while it cures. Most bad panels come from the setup, not the glue.

Materials

• Boards milled to the same thickness, a little long and a little wide
• Wood glue: Titebond II for most shop work and anything that sees weather, Titebond II Extend when you need more time
• Packing tape or wax paper for the cauls
• A bowl of water and a Scotch-Brite pad, or a putty knife, for squeeze-out

Tools

• Jointer or a sharp hand plane (jointer plane or a No. 5)
• Bar or pipe clamps, enough to put one every 12" or so, top and bottom
• A couple of straight, stiff cauls (2x stock, jointed)
• Straightedge, pencil, glue roller or brush

Steps

1. Lay out the boards for looks first. Shuffle them till the color and figure flow across the panel, then make sure the grain runs the same direction on every board so you can plane or scrape the whole panel one way without tearout.
2. Mark a big triangle across all the boards. That cabinetmaker's triangle tells you the order and which face is up, so nothing gets flipped when the glue's on.
3. Joint every edge square to the face. Dry-fit the panel with light clamp pressure. You shouldn't see light through any seam, and the faces should sit flush.
4. Do a full dry run with the clamps. Set every clamp to length now. Alternate them, one on top, the next one underneath. A single clamp pulls the panel toward its bar, so alternating cancels out the bow.
5. Space the clamps right. Clamp pressure spreads out at roughly 45° from each clamp head, so it reaches as far sideways as the clamp is from the glue line. On 6" boards that's about a 12" spread at the joint, so clamps about 12" apart. Narrow boards or edging need the clamps closer, or a stiff caul to spread the load first.
6. Glue both edges and watch the clock. Titebond's own sheets list 3 to 5 minutes of open time for Titebond II Premium at 70°F, and 15 minutes for Titebond II Extend. On a big panel, that's the difference between a calm glue-up and a panic.
7. Snug, check, then tighten. Bring the clamps up snug from the middle out, tap the boards flush, check flat with a straightedge, then finish tightening. Titebond says to use just enough pressure to bring the joint tight: generally 100 to 150 psi for softwoods, 125 to 175 for medium woods and 175 to 250 for hardwoods.
8. Read the squeeze-out. A small, even bead all along each seam means you used the right amount of glue. None means a starved spot. Then either lift it right away with a damp, wrung-out Scotch-Brite pad using short rolling strokes, or wait until it goes rubbery (putty-like, roughly 10 to 20 minutes) and pop it off with a putty knife.
9. Leave it alone. Titebond says 30 to 60 minutes in the clamps for an unstressed joint, and don't stress the new joint for 24 hours. I leave a panel overnight before I plane it.

How much pressure is that, really? A 3/4" by 36" edge is 27 square inches of glue line. At 150 psi that's about 4,000 pounds of total clamping force. That's why one pipe clamp in the middle won't cut it, and why a couple of extra clamps never hurt.

MOAM's shop note: Don't crank the clamps down until the glue runs off the bench. Over-tightening slides the boards out of flush and bows the panel, and a wet rag smeared across a seam just works watered-down glue into the pores, where it shows up as a blotch the minute stain or varnish goes on. Snug, even beads, and a light touch on the cleanup.

Sources: Titebond product sheets and FAQ (titebond.com), Fine Woodworking, "How to Glue-Up Joints: Positioning the Clamps," Rockler, "Clamping Tips for Edge Gluing Panels," and Popular Woodworking on Titebond's squeeze-out advice.

MOAM Out.

Woodworking Tip of the Day: Wetting Out Fiberglass Cloth: No Dry Spots, No Floating, No Bubbles

This is catching the MOAM's attention today….. how many good wooden boats get a fiberglass skin that's half stuck, half floating and full of little white dry spots. The Chamberlain Marblehead gunning dory is going to get cloth on her bottom, so before I mix a drop I went back to the people who make the stuff and wrote down how they say to do it. Here it is, the way I'll do it in my shop.

Why it matters: Glass cloth over wood is there for abrasion and impact, and to keep the wood under it sealed. It only does that job if every thread is soaked and the cloth is pressed tight to the wood. Too little epoxy and you get dry, white weave that's weak and wicks water. Too much and the cloth floats up off the wood on a puddle of resin, which is heavy, brittle and a pain to fair. Work it too hard and you whip in tiny air bubbles that show up forever under a clear finish.

The numbers, from the epoxy makers

• Cloth: System Three's guide says 6 oz cloth is enough for most surfaces, doubled in high-wear spots. That's what goes on most small wooden boats.
• Cut it oversize: WEST SYSTEM says to cut the cloth several inches larger than the surface on every side, and to overlap pieces about 2".
• Small batches: WEST says three or four pumps each of resin and hardener at a time. Small batches don't kick off in the cup while you're still spreading.
• How much epoxy: WEST's table puts 6 oz cloth plus two fill coats at about 1.61 fluid ounces of mixed epoxy per square foot, waste included. So 40 square feet of bottom is roughly 64 fluid ounces, half a gallon. Buy a little extra.
• Fill coats: two or three coats to fill the weave, so your final sanding doesn't cut into the cloth.
• Trim time: System Three says trim the overhang at the "green" stage, when it's pliable but not tacky unless you press hard. An Epoxyworks article puts the minimum time between coats at about 3 hours, or when you can trim the cloth without resin sticking to the knife, at room temperature. Cold shop, longer wait.

Materials

• 6 oz fiberglass cloth (plain weave), enough to cover with several inches spare all around
• Epoxy resin and hardener, with the maker's pumps
• Masking or duct tape, or staples, for sloped and vertical areas
• Mixing cups and sticks, nitrile gloves, and some paper towels

Tools

• Plastic squeegee (a flexible one, not a putty knife)
• Thin foam roller covers and a tray for vertical surfaces and fill coats
• Sharp scissors and a fresh utility or single-edge razor blade
• Metal straightedge for trimming overlaps
• Respirator for sanding later (see the 10/23 dust tip), and a fan or open door for ventilation

Steps: wetting out cloth the dry way

1. Prep the wood like it's a glue joint. Fair, sand, vacuum and wipe it clean. Any epoxy already on there that's cured gets washed for blush (see the 10/24 tip) and sanded dull.
2. Lay the cloth on dry. Unroll it, smooth it with your hands from the middle out, and let it hang several inches past every edge. Overlap pieces about 2". Tape or staple it on anything that slopes.
3. Mix a small batch. Three or four pumps each. Mix it well, scraping the sides and bottom of the cup.
4. Pour in the middle. Pour a small pool near the center of the cloth on a flat area. On vertical or steep spots, roll it on instead.
5. Spread it out, gently. Push the epoxy from the pool into the dry cloth with the squeegee. Let it soak in. Don't try to force it through. The cloth goes clear when it's wet out; white means dry, so add a little more there. Over bare wood, leave enough for the wood to soak up too.
6. Smooth wrinkles as you go. Work them out toward the edges. On a tight curve or corner, snip a dart with the scissors and lap it for now.
7. Squeegee off the extra before it gels. Hold the squeegee low, almost flat, and pull slow, even, overlapping strokes. Take off the shiny excess that would let the cloth float, but don't press so hard you make dry spots. What you want is evenly clear cloth with the weave texture still showing.
8. Keep going, batch by batch. Mix the next small batch and work into the wet edge of the last one.
9. Trim at the green stage. When it's pliable but not tacky unless you press hard, run a fresh blade along the edge of the panel. To trim an overlap into a flush butt joint, cut down the middle of it against a straightedge, peel out both scraps, and re-wet the edge. Or leave the overlap for strength and fair it in later.
10. Fill coats before full cure. Roll on thin fill coats as soon as the last one is tack-free. Two or three will fill the weave. If it sits past full cure, wash off the blush and sand before the next coat.
11. Sand the epoxy, not the cloth. When the weave is filled and cured, sand for paint or varnish. If you see white fibers, you've gone through the epoxy into the cloth. Stop and recoat there.

On the dory: Her bottom is the part that hits the beach, the rocks and the trailer, so that's where the cloth goes. I'll lay it on dry, tape it along the chines so it can't creep, and work from the middle of the bottom out to the edges in small batches. It's going to be painted, so a few micro-bubbles won't show, but I'll still keep the squeegee work to a minimum. And I'll do it on a warm afternoon with the shop heater running, because a cold October shop in Marblehead slows the cure way down.

MOAM's shop note: The mistake I see most is the guy who dumps a big puddle and chases it all over the hull with the squeegee, back and forth, back and forth. Now the cloth's floating in one place, dry in another, and the whole thing is foamy. Small batches, pour it, spread it, let it soak, one or two passes with the squeegee held flat, and walk away. If it's clear and the weave still shows, you're done with that section.

The numbers here come from WEST SYSTEM's instructions and coverage table, System Three's fiberglassing guide, and an Epoxyworks article on glassing a hull. The 40-square-foot example is my own arithmetic from WEST's table. Your epoxy's own instructions win if they say something different, especially on cure times.

Sources: WEST SYSTEM, Applying Fiberglass Cloth & Tape and Estimating Epoxy Coverage for Fabric Application; System Three, Fiberglassing with System Three Epoxy; Epoxyworks, Fiberglassing a Woodstrip Hull.

MOAM Out.

Woodworking Tip of the Day: Router Safety: Feed Direction, Climb Cuts and Keeping Your Fingers

Not for nuthin'…. But….. the router is the tool that's going to bite you when you're not paying attention. It doesn't kick back like a table saw, and it doesn't jam like a bandsaw. It just grabs and runs. I'm putting roundovers on the gunwales and rubrails of the Chamberlain Marblehead gunning dory right now, plus a hatch coaming or two, and every one of those cuts goes better when the router is going the right way. So today: which way to feed, when a climb cut is fine and when it isn't, how to seat a bit so it stays put, and how fast to spin the big ones.

Why it matters: A router bit turns upwards of 20,000 rpm. Feed it the right way and the bit pushes back against you, so you're the one in charge. Feed it the wrong way and the bit pulls the router, or the board, along with it. Fine Woodworking puts it plainly about the router table: climb cut while feeding by hand and the stock can be ripped from your hand, drawing your hand into the cutter. Add a bit that wasn't seated right, or a big panel bit spinning too fast, and you've got a projectile.

The rules, with the numbers

• Handheld router: seen from above, the bit spins clockwise. Woodcraft's rule is to feed against that spin: go counterclockwise around an outside edge, and clockwise around the inside of an opening. On the edge nearest you, that means left to right.
• Router table: the router's upside down, so the bit spins counterclockwise. Feed right to left along the fence, into the rotation, so the bit pulls the stock into the fence. Fine Woodworking's router-table basics also say to keep the stock between you and the bit, never trapped between the bit and the fence.
• Climb cuts: going with the spin cuts clean and kills tearout, but the router wants to take off. Fine Woodworking says it's fine handheld with light passes, a boxer's stance and both hands on the tool. Never with the bit tethered, like on a circle jig, and never on the router table when you're feeding by hand, unless the work is big or locked in a heavy jig or sled.
• Seating the bit: Amana says bottom the shank out in the collet, then back it off about 1/16". Bosch's manuals say the cutters should sit about 1/8" to 1/4" from the collet nut face, with at least 5/8" of shank gripped. Never tighten a collet with no bit in it.
• Speed: Freud's chart for maximum speed by cutting diameter: up to 1", 24,000 rpm; 1" to 1-1/4", 18,000; 1-1/4" to 2-1/4", 16,000; 2-1/4" to 3-1/2", 12,000. And never faster than the speed marked on the bit.
• Depth: on the router table, Fine Woodworking says to keep it around 1/8" per pass in hardwood; you can go deeper in softwood. Shallow passes don't burn, don't chatter, and don't yank.
• Noise: a compiled sound-level database puts the average router at about 97 dBA. NIOSH's recommended limit is 85 dBA over an 8-hour day, and the allowed time halves for every 3 dBA above that. Do the arithmetic and 97 dBA gets you about half an hour. Muffs or plugs, every time.

Materials

• A scrap of the same stock for a test pass
• Clamps, or a non-slip router pad, to hold the work
• Featherboards and a push block or push stick

Tools

• A router (handheld or in a table) with the right collet for the bit's shank; 1/2" shank whenever you can
• Sharp, clean bits; a dull one makes the router wander and burn
• Collet wrenches
• Safety glasses and hearing protection
• Dust collection or a shop vac on the router, and a dust mask (see the 10/23 tip)

Steps: a safe routing session

1. Unplug it before you touch the bit. Not just "switched off." Unplugged, or battery out.
2. Seat the bit right. Clean the shank and the collet. Push the shank all the way in, back it off about 1/16", and tighten the nut with both wrenches. The cutters shouldn't touch the nut, and you want plenty of shank in the grip.
3. Set the speed for the bit. Small bits run fast. Anything over an inch in diameter gets slowed down per the chart, and a big panel-raising bit belongs in a table, near the bottom of the dial.
4. Hold the work. Clamp it or put it on a router pad. Small parts don't get routed handheld: rout the edge of a wider board and rip the part off after, or use the table with a push block.
5. Glasses and muffs on. Dust collection on. Sleeves rolled, nothing dangling.
6. Start clear of the work. Let the router come up to speed before the bit touches wood.
7. Feed against the spin. Handheld: counterclockwise around the outside, clockwise inside an opening. Table: right to left, stock against the fence, featherboard holding it there, right hand feeding, left hand guiding, hands never over the bit.
8. Take it in passes. Around 1/8" per pass in hardwood on the table. Keep the router moving at a steady rate: too slow and it burns, too fast and it chatters and tears.
9. Climb only on purpose. If a corner or a nasty grain reversal tears out, take a very light climb pass first (handheld, both hands, steady stance), then finish with a normal push cut.
10. Let it stop. Wait for the bit to quit spinning before you set the router down, and don't grab the bit right after; it's hot.

On the dory: The gunwales and rubrails get a roundover, and that's a long run of handheld router work along a curve. I go left to right along the edge facing me, and I take two light passes instead of one heavy one. On the mahogany, where the grain swaps direction on me, I'll take a whisper-thin climb pass at the tearout spot, then clean it up going the right way. And the earmuffs stay on even for "just one quick pass." Years of quick passes add up.

MOAM's shop note: The mistake I see most is on the router table with a narrow piece: the guy feeds it left to right, or he runs the stock on the far side of the bit, between the bit and the fence. Either way it's a climb cut, and the bit can grab that strip and pull it right out of his hand. Right to left, stock between you and the bit, featherboard and push block on anything narrow. And if you hear the router bog and smell burning, you're taking too much at once. Back it off and take another pass.

The numbers here come from Woodcraft, Fine Woodworking, Amana Tool, Bosch's router manuals, Freud's router-bit speed chart, NIOSH and a compiled sound-level database. The half-hour figure at 97 dBA is my own arithmetic from the NIOSH rule. Your router's manual and the bit's packaging win if they say something different.

Sources: Woodcraft, Understanding Router Feed Direction; Fine Woodworking, Climb-Cutting: Don't Believe the Naysayers and Router-Table Basics; Amana Tool, Knowledge Base; Bosch, RA1152 operating instructions; Freud, Router Bits: Technical Information; NIOSH, Noise and Hearing Loss.

MOAM Out.

Woodworking Tip of the Day: Keeping Rust Off Your Tools in a Salt-Air Shop

Salt air's good for the soul and murder on a plane iron….. Work a few hundred yards from Marblehead Harbor and you learn it fast. Leave a block plane on the bench Friday, open the garage door on a mild, damp Saturday morning, and there's an orange freckle on the sole and a fingerprint etched into the iron. I'm building a Chamberlain Marblehead gunning dory, and the bronze fastenings don't care about the weather. The plane irons, chisels, saws and cast-iron tops do. So today: why tools rust, what the humidity numbers really are when there's salt in the air, and which coatings actually held up when Fine Woodworking tortured twenty of them.

Why it matters: Rust is iron, oxygen and water getting together. Fine Woodworking's Thomas McKenna lays out the two things that speed it up in a shop like mine: salt, whether it's from sea air or the moisture off your fingertips, and temperature swings that cause condensation. In an unheated garage, when a cold night turns into a warm day, condensation settles on the saw table, the jointer and any hand tool left on the bench. Once it starts, it spreads like a rash. A little surface rust on a chisel back or plane sole is an hour of flattening you didn't need to do. Pitting is worse, and if it reaches the edge, you're grinding the pits out.

The numbers that matter

• Clean steel: CoatingsPro (an AMPP corrosion-industry magazine) puts the critical relative humidity for steel at around 60%. That's the level below which water won't form on a clean metal surface. At 75 to 80% the corrosion rate jumps sharply.
• Salty steel is a different animal. Sea salt pulls water out of the air. Plain salt (sodium chloride) turns to liquid brine at about 76% humidity, but a 2014 study in the Journal of The Electrochemical Society found steel dusted with salt crystals could start rusting at as low as 33%, and from 53% up it rusted nearly as fast as steel sitting under wet brine. Translation for the coast: a shop that feels dry can still rust a tool that has salt on it. Wiping the salt off matters as much as the humidity.
• Dew point: The National Weather Service defines it as the temperature the air has to cool to before it hits 100% humidity. Anything colder than that collects water. Work it out (my arithmetic, using the standard Magnus formula): 60°F shop air at 70% humidity has a dew point of about 50°F. A plane iron that sat at 45°F overnight will sweat the minute that air hits it. Woodworker's Journal's Tim Inman calls it the sweaty iced-tea glass, and points out it's the changing temperature that does the damage, not the cold itself.
• A dry shop: Woodworker's Journal's Chris Marshall runs a dehumidifier year-round in a closed shop, and his humidity hovers around 40 to 50% in the mild months. That's the range I aim for.

What actually works: the Fine Woodworking test

In 2012 Fine Woodworking put 20 rust preventers through ten days of abuse. They coated a cast-iron table saw top, spritzed it with water and left it outside under an overhang. Then they coated A2 tool steel samples and froze and thawed them every day so condensation built up. The saw top showed rust after one night, and the tool steel within 48 hours.

• Top seven: CRC Industrial 3-36, LPS 3, Moovit, Rust Block, WD-40, WD-40 Long-Term Corrosion Inhibitor and 3M Rust Fighter 1.
• Their picks: CRC 3-36 was best overall. It has a petroleum odor, so if you'd rather keep petroleum off your hand tools, they recommended Moovit. LPS 3 and 3M Rust Fighter 1 performed perfectly but left a sticky feel, and LPS 3 was the only product that kept yellow glue from sticking.
• Finishes: None of the products interfered with an oil-based or water-based topcoat, even when they put them right on the wood.
• The surprise: Paste wax is a fine lubricant on plane soles and machine tables, but it didn't offer much rust protection. Camellia and jojoba oil were marginal, and Boeshield T-9 didn't make the top seven.

Now, to be fair to the oils: Lie-Nielsen tells its customers to keep iron tools lightly oiled or waxed and recommends jojoba, and they say it won't interfere with finishes or gluing. And a ship's carpenter writing in Fine Woodworking took camellia oil and several other rust preventers along for nine months on a tall ship, with salt spray and sweaty hands working on his tools, and camellia oil beat them all. Here's how I square it: a thin wipe of natural oil is fine on a tool you pick up every day. A tool that's going to sit in a damp garage for a month gets something that passed the test.

Materials

• A rust preventer that passed the test: CRC Industrial 3-36 for machine tops and idle tools, Moovit for hand tools
• Jojoba or camellia oil for the daily wipe-down, if you like a natural oil
• Paste wax for plane soles and saw tables (to make the wood slide, not to stop rust)
• Clean cotton or microfiber rags
• Rechargeable silica-gel desiccant canisters, or VCI emitters, for the tool chest and drawers
• Evapo-Rust (or a similar water-based soak) for tools that already have rust on them
• A fine abrasive handblock (rubberized abrasive) for light surface rust

Tools

• A digital hygrometer (one in the shop, a cheap one in the tool chest)
• An infrared thermometer to check the iron itself
• A dehumidifier sized for the shop
• A tool chest, till or cabinet with a lid that closes tight

Steps: keep the water off the iron

1. Hang a hygrometer and read it. Know the humidity before you leave for the night. If the shop sits above 50% for days at a time, that's your first job, before any spray can.
2. Close the shop up and dry the air. Shut the doors and windows on muggy days and run the dehumidifier. Empty it regularly, or plumb it to a drain. Fine Woodworking also suggests masonry waterproofing paint on basement walls and sealing garage floors, so moisture can't come up through the concrete.
3. Watch the morning swing. The worst time is a cold night followed by a mild, damp day. Don't throw the garage door open to let the warm air in while the iron's still cold. Shoot the plane sole with the infrared thermometer. If it reads at or below the dew point, keep the tools covered or in the chest until they warm up. Same goes for cranking a heater in a cold shop: the air warms up long before the cast iron does.
4. Wipe every tool before it goes away. Your fingers leave salt and moisture on the steel. A quick wipe with a clean rag takes the prints and the sawdust off. Vic Tesolin points out in Fine Woodworking that dust soaks up moisture and holds it against the steel, which is why old tool chests had a dust seal.
5. Dry it all the way after the waterstones. Sharpening on waterstones (the 10/17 tip) leaves water on the blade, the chipbreaker and the screw. Dry it completely, then oil it. Oil over a wet blade just traps the water.
6. Coat it thin. Hand tools you use every day: a few drops of jojoba or camellia oil, or Moovit, on a rag, wiped on and wiped back off. Cast-iron tops and tools that will sit: a spray that passed the test, like CRC 3-36. Wax on top of that only if you want the wood to slide.
7. Store it closed, with a dry pack. Put a desiccant canister or a VCI emitter in the chest or drawer and keep the lid shut. Fine Woodworking explains that both are made for enclosed spaces: a desiccant fills up and has to be dried out with heat (only some kinds can be), and a VCI gives off a vapor that coats the metal, lasts anywhere from six months to five years depending on the product, and leaks away if the drawer stays open. None of the sprays protect the inside of a power tool, either, so the cases need a dry pack too.
8. Catch it early. A little orange bloom comes off with a fine abrasive handblock; Lie-Nielsen says it uses one in its own shop. Anything heavier goes in an Evapo-Rust bath: the maker says 30 minutes for light rust, up to overnight for heavy. Then rinse with water; the maker calls that step especially important. Let it dry, then coat it.

On the dory: The boat sits where the fog rolls in off the harbor, and the shop sees every swing between a raw November night and a soft, damp morning. So the chisels and the block plane I use every day get a wipe and a few drops of oil when I put them down. The jointer, the bandsaw table and the planes that only come out for the next boat get a coat of something that passed the test. The bronze screws in the planking don't need any of it. And everything that matters lives in a lidded till with a desiccant canister, not out on the bench where the next fog bank can find it.

MOAM's shop note: The most common mistake I see is the guy who waxes his plane soles faithfully and thinks that's rust protection. Wax makes the plane glide; in Fine Woodworking's test it didn't do much to stop rust. The second is the guy who cranks a heater in a freezing garage for a Saturday project. The warm, moist air hits forty-degree cast iron before the iron can catch up, and by Monday the table saw has a rash. Keep the temperature steady if you can, keep the humidity under 50%, and wipe the salt off your tools before you coat them. And if you're near the water, remember: a dry-feeling shop isn't dry enough if there's salt on the steel.

The numbers here come from Fine Woodworking's rust-preventer test, CoatingsPro, the Journal of The Electrochemical Society, the National Weather Service, Woodworker's Journal, and Lie-Nielsen's and Evapo-Rust's own instructions. The dew-point example is my own arithmetic. Read the label on whatever you buy, and test it on a scrap of steel before you trust your good tools to it.

Sources: Fine Woodworking, Thomas McKenna, Got Rust? (July/August 2012); Camellia Oil Outscores Other Rust Preventers; Wax Keeps Rust Off Hand Tools; Vic Tesolin, Keep It Comfortable for You and Your Tools. CoatingsPro (AMPP), How (and Why) to Protect Metallic Surfaces (2012). Schindelholz, Risteen and Kelly, Effect of Relative Humidity on Corrosion of Steel under Sea Salt Aerosol Proxies, Journal of The Electrochemical Society (2014). National Weather Service, Dew Point vs. Humidity. Woodworker's Journal, How Will Cold Air Affect Tool Rusting? Lie-Nielsen, Jojoba Oil and Bench Planes instructions. Evapo-Rust, Four Easy Steps to Rust-Free Tools.

MOAM Out.

Woodworking Tip of the Day: Sanding Sequence: Which Grits You Can Skip and Which You Can't

This is catching the MOAM's attention today….. how many good finishes get ruined with sandpaper. Either somebody jumped from 80 grit straight to 220 to save twenty minutes, or somebody polished cured epoxy so slick the varnish had nothing to hang on to. I'm building a Chamberlain Marblehead gunning dory, and between bare wood, epoxy-coated planks and primer, I go through a lot of paper in this shop. So today: which grits you can skip, which ones you can't, and where to stop for wood, for epoxy under varnish, and for epoxy under paint.

Why it matters: Each grit's only job is to take out the scratches the last grit left. Skip too far and the finer paper just knocks the tops off the deep scratches. Lon Schleining put it plain in Fine Woodworking: no matter how long you sand, 180-grit won't remove the scratches made by 100-grit. They hide until the stain or the first coat of varnish lights them up. Go the other way, too fine on a surface that's getting another coat, and you've sanded off the "tooth" the coating needs to grab. WEST SYSTEM, Epifanes and Interlux all warn about that one.

The rules for skipping

• Start coarse enough, not coarser. Bob Flexner (Popular Woodworking) starts planed solid stock at 80 and factory-sanded plywood at 120, because 80 on veneer is wasted work and risks sanding through. Schleining starts hard maple at 120, since 80 and 100 scratches are tough to get out of it.
• Never skip two in a row. Uneeda, the abrasives maker, calls it the golden rule: never skip more than one grit. 80, 120, 180 is fine. 80 straight to 180 isn't.
• By hand, with the grain, you can skip one. Jeff Jewitt (Fine Woodworking) says hand sanding leaves scratches that run with the grain, so you can go 100, 150, 220. The American Woodworker editors checked with sandpaper makers and got the same answer: 80, 120, 180 or 100, 150, 220.
• On a random-orbit sander, don't skip. Jewitt again: those machines put cross-grain scratches in the wood, and if you skip, you'll likely see the coarse ones later. Flexner calls every grit (80, 100, 120, 150, 180) the most efficient way to go, as long as you only sand each one long enough to take out the last.

Where to stop depends on what goes on next

• Bare wood under a film finish (varnish, shellac, lacquer): Flexner says it's rarely worth going finer than 180, because after a couple of coats the finish makes its own surface. Go to 220 if random-orbit swirls still show, and finish by hand, with the grain, at your last grit. Water-based finish is the exception; Jewitt goes to 320 or 400 to cut down the raised grain. (Raising the grain was the 10/13 tip.)
• Bare wood under marine varnish: Epifanes says bare wood should normally be prepared to about 100 or 120 grit, and that much finer won't give that first coat enough grip. Then 220 dry over the first few coats to knock down the raised grain, and 320 wet or dry once the grain fills, right to the end. 400 is the finest they'd ever use between coats. Anything finer, there's no tooth.
• Epoxy-coated brightwork under varnish: TotalBoat says let the epoxy cure 5 to 7 days, wash it with mild soap and warm water even if it's sold as "non-blushing," dry it, then sand with 220 or 320. Only reach for 80 to cut down runs and sags (WEST), then climb back up through the grits.
• Epoxy under paint: WEST SYSTEM's manual says the coating maker's directions rule, and gives the ballpark: 80 to 100 grit is usually enough under a high-build or filling primer, 120 to 180 for primers and high-solids coatings, and 180 is often recommended for high-gloss finishes. Finer than that may not give enough tooth and can lead to sags and runs. Interlux's system for a clear-epoxy surface: let it cure 3 to 7 days, wash off the blush first (Interlux says sanding doesn't remove contamination), sand 80 to 120, fill and sand 120 to 220, then a two-part primer (Epoxy Primekote), 120 between primer coats, and 220 to 320 on the last primer coat before the topcoat. Their one-part Brightside topcoat gets sanded 220 to 320 between coats.

Materials

• Sanding discs for your random-orbit sander: 80, 100, 120, 150, 180, 220
• Sheets for hand and wet sanding: 120, 180, 220, 320, 400 wet-or-dry
• Maroon Scotch-Brite pads and clean water (for washing epoxy before sanding)
• A soft pencil
• The coating's data sheet or can label, so you know your last grit before you start

Tools

• 5-inch random-orbit sander hooked to a shop vac
• A flat sanding block (cork-faced or rubber) for flat work, and a longboard for fairing a hull
• A bright light you can set low for raking across the surface
• Shop vac with a brush head, and tack cloth for between coats
• Half-mask respirator with P100 filters for epoxy, primer and fairing dust

Steps: climb the ladder without missing a rung

1. Read the can before you pick up the sander. The coating sets your last grit, so know where you're stopping before you start: 180 for most film finishes on bare wood, about 100 to 120 under Epifanes varnish, 220 to 320 on epoxy under varnish, and whatever the primer's sheet says under paint.
2. Pick the starting grit by the worst defect, not by habit. Planer marks on solid stock: 80. Factory-sanded plywood: 120. Hard maple: 120. Cured epoxy with runs or sags: 80, just on those spots. A smooth epoxy coat that only needs tooth: go right to your finish grit.
3. Epoxy gets washed before it gets sanded. Let it cure all the way, then scrub with water and a maroon Scotch-Brite pad, and dry it. Sanding first just grinds the blush in. (The full story on amine blush was the 10/24 tip.)
4. Scribble pencil across the surface. The American Woodworker editors use pencil lines to tell when glued-up boards are flush. I use them for every grit: when the scribble's gone everywhere, that grit's done its job.
5. Sand, then check with a raking light. Set the light low and look across the surface before every grit change. One stray scratch is easy to fix now. Find it after the next grit and you're backing up two.
6. Vacuum, then move up one grit. On the random-orbit sander, go every grit. By hand, with the grain, you can skip one. Never skip two. Vacuum between grits so a loose coarse grain doesn't get dragged across your fine work.
7. Finish by hand, with the grain. After your last machine grit, hand-sand with a flat block at the same grit to take out the random-orbit swirls (Flexner).
8. Test it, clean it, coat it. On epoxy, rinse with fresh water: WEST says it should sheet out evenly. If it beads, wet-sand that spot again. Then wipe with whatever cleaner the coating maker calls for and get the coat on.
9. Between coats, sand light and not too fine. Wait until it's hard enough to sand. Epifanes says one-part varnish or paint is generally safe after 24 hours. Interlux's Brightside sheet says 12 hours at 75°F, 16 at 60°F and 20 at 50°F. Then use 220 to 320, and never finer than 400.

On the dory: The epoxy-coated planking that's headed for paint and any bright trim headed for varnish get two different ladders. The trim gets washed and taken to 220 or 320 for varnish. The hull gets washed, sanded 80 to 120, and goes under a two-part primer before any one-part topcoat, because Interlux's Brightside sheet calls for Epoxy Primekote or InterProtect over clear epoxy before the one-part topcoat goes on. And Primekote and Brightside both want the air, the paint and the hull at 50°F or warmer, so in a Marblehead shop in November, that's a warm-day job.

MOAM's shop note: The most common mistake I see is the guy who sands his last coat of epoxy to 600 because it feels like glass, then wonders why the varnish peels in the spring. Smooth isn't the goal. Tooth is. Epifanes says anything finer than 400 won't give enough mechanical bond, and WEST says going finer than about 180 under paint may not give enough tooth for good adhesion. If you want it slick, do it with the finish, not the sandpaper. The other mistake is the guy who goes 80 to 220 on a random-orbit sander, puts stain on, and finds a tabletop full of little curlicues. Every grit, on the machine. It's faster than doing it twice.

The numbers here come from the makers' data sheets and help pages (WEST SYSTEM, Interlux, Epifanes, TotalBoat and Uneeda) and from Fine Woodworking, Popular Woodworking and American Woodworker. Read the label on your can. If the coating maker says something different, the coating maker wins.

Sources: WEST SYSTEM, User Manual (Final surface preparation). Interlux (AkzoNobel), Epoxy Primekote data sheet, Brightside Polyurethane data sheet and product information sheet, and the Perfection application bulletin. Epifanes NA, Q & A. TotalBoat, Varnishing over epoxy. Uneeda, Grit Sequence. Bob Flexner, Rules for Sanding Wood (Popular Woodworking). American Woodworker, 12 Tips for Faster, Smoother, Better Sanding. Fine Woodworking, Lon Schleining, Tips for Better Sanding, and Jeff Jewitt, Sanding Basics.

MOAM Out.

Tools for this tip

As an Amazon Associate I earn from qualifying purchases.

• Diablo SandNet 5 in. assorted sanding discs with connection pad, 10-pack (2 each 80/120/180/220/400), DND050ASTH10I: one pack covers the climb: 80, 120, 180 and 220, plus 400 for between coats; fits 5- and 8-hole random-orbit sanders
• 3M 05519 rubber sanding block, 2-3/4 x 5 in. (wet or dry): a flat block for hand sanding with the grain and wet-sanding primer and epoxy
• 3M Pro Grade Precision sanding sheets, assorted 220/320/400: 220/320/400 sheets for sanding between coats of varnish and paint
• 3M Scotch-Brite 7447 general purpose hand pads, maroon, 6 x 9 in. (20-pack): the maroon pad for washing cured epoxy with water before you sand it
• Oneida Air Systems Dust Deputy DIY anti-static cyclone separator for wet/dry shop vacs: cyclone between the sander and the vac, so the fine dust lands in the bucket
• 3M 6503QL Rugged Comfort Quick Latch half facepiece reusable respirator, large: half-mask respirator for sanding epoxy, primer and fairing compound

Use whatever you already have in the shop; these are just the ones that fit this job.

Woodworking Tip of the Day: Amine Blush: How to Spot It, Wash It Off and Keep It From Ruining Your Next Coat

Raw, damp October in the boat shop, and you know what that brings….. amine blush. This time of year on the Chamberlain Marblehead gunning dory, you roll a coat of epoxy on in the afternoon, come back in the morning, run your hand over it, and it feels like somebody wiped it down with a candle. That greasy film is amine blush. It won't hurt the epoxy, but it will ruin the next thing you put on top of it if you don't deal with it. The good news is it comes off with a bucket of water and a pad. The bad news is that most folks reach for the sandpaper or the acetone first, and neither one does the job.

What it is: The hardener side of most marine epoxies is full of amines. While the epoxy is still curing, the amines sitting at the surface can react with carbon dioxide and moisture in the air instead of with the resin. Gougeon Brothers (the WEST SYSTEM folks) say that forms a wax-like film, and MAS describes the product as a carbamate. It's a thin layer, and WEST says it doesn't affect the strength of the cured epoxy. It's water-soluble, which is the whole key to getting it off.

Why it matters: Blush gets in the way of whatever comes next. WEST says it reduces the secondary adhesion of the next coat of epoxy, can keep polyurethane finishes from drying, can make the epoxy look slightly cloudy, and can interfere with the cure of some paints and varnishes and all polyester gelcoats. It also clogs sandpaper. Interlux (Epiglass, Brightside) warns that blush left under its one-part primer can work up through the primer, so the topcoat doesn't cure right over those spots, and both primer and paint can let go. On a boat, that's a peeling job next spring.

What makes it worse: Everything a New England shop does in the fall.

• Cold. Cold slows the cure, and the longer the epoxy stays uncured, the more time the amines have to react with the air. WEST's advice is to work above 65°F if you can.
• Damp air, and temperature dropping overnight. WEST says a cool, damp day makes more blush than a hot, dry one, and blush shows up most when a coat cures while the temperature is falling. A hull that's colder than the shop air can sweat condensation right onto your wet coat.
• Thin films. A thin coat doesn't make much heat, so it cures slower and blushes more than a thick one.
• Open-flame heaters. Kerosene torpedo heaters add carbon dioxide to the air, and WEST says unvented kerosene or propane heaters can also slow the cure and leave unburned hydrocarbons on the surface. That's the classic cold-shop mistake.
• Too much hardener. Off-ratio mixes make more blush and a weaker epoxy. Pump it right and stir it well.
• Fast hardeners, with a cold-shop catch. A 2025 Epoxyworks article says slower hardeners like WEST's 209 and 207 make less blush than faster ones, and TotalBoat and Chesapeake Light Craft (for MAS) say the same about their own fast and slow hardeners. The catch: a slow hardener that barely cures in a 50-degree shop gives the amines all night to react, which is why an older Epoxyworks piece recommended 205 Fast below 72°F. WEST lists a 60°F minimum for 206 Slow and 40°F for 205 Fast. So pick a hardener that will actually cure at your shop temperature, and plan on washing either way.

Materials

• A bucket of clean, warm water (WEST says water clean enough to drink) and a second bucket or a hose for rinsing
• Maroon Scotch-Brite general-purpose pads (WEST names the 7447 by number)
• Plain white paper towels, a big roll
• 80-grit aluminum oxide paper for any glossy spots left after washing (no stearate-coated paper)
• Nitrile gloves
• Release fabric (peel ply) if you're laminating and want to skip the wash next time

Tools

• A thermometer and hygrometer for the shop, and an infrared thermometer for the hull's surface temperature
• Sanding block or random-orbit sander
• Shop vac

Steps: spot it, wash it, then sand

1. Assume it's there. WEST's manual says it isn't unreasonable to assume blush has formed on any cured epoxy surface. TotalBoat says it can be there even when the surface looks clean and glossy, and it can form unevenly, so one spot is fine and the next few inches aren't. Plan on washing every cured coat.
2. Check it anyway. Run a clean, gloved fingertip over it. Blush feels greasy, waxy or slick. Look for a dull or cloudy haze instead of gloss, and in bad cases, white salt-like spots. Then do the water test: wet it and watch. Water that beads up or channels means it needs cleaning; water that sheets out evenly means the surface is clean. WEST calls that the water break test.
3. Wait for a hard cure. Blush comes off after the epoxy has cured hard, so don't scrub a coat that's still soft. In a cold shop that can take a lot longer than the can says.
4. Scrub with warm water and a Scotch-Brite. Wet the surface and scrub every inch, working in sections. TotalBoat says warm water dissolves it faster than cold. WEST says plain water is all you need and that soap, ammonia or bleach can leave a residue of their own. TotalBoat, Interlux and System Three add a little mild soap; if you do, rinse well, because soap left behind causes the same trouble as the blush.
5. Change the water often. The water picks up the dissolved blush. Scrubbing with a dirty bucket just spreads it back around.
6. Dry it with paper towels, right away. Wipe it off while it's wet so the dissolved blush comes off on the towel and doesn't dry back onto the surface. Use plain white paper towels, the way WEST and Epoxyworks call for. Then let it dry all the way. Don't put the next coat over a damp surface.
7. THEN sand. Sand any spots that are still glossy with 80 grit so the next coat has scratches to key into, and vacuum. For paint or varnish, finish with whatever grit the coating maker calls for. Wet-sanding with wet/dry paper also takes blush off. What doesn't work is dry-sanding first: it clogs the paper and, per Epoxyworks and Interlux, works the blush deeper into the surface.
8. Skip the acetone. Blush is water-soluble, and WEST says many organic solvents don't remove it well. Interlux says it straight: acetone won't remove it. Save the solvent for real grease or oil, and wipe it on and off with fresh paper towels.

When you can skip the wash

• Recoat while it's still tacky. In the gel, or "green," stage, the next coat of epoxy chemically links with the last one, so you can recoat without washing or sanding. The coat should be tacky but firm enough to hold the next one. WEST says you can still dent it with a thumbnail at that stage. That window runs anywhere from about 15 minutes to several hours, depending on the hardener and the temperature, so check your own product's data. WEST's tip for coating: put all your coats on the same day. Their caution matters up here too: once a coat is past the soft-gel stage in a cool, damp climate, don't count on it. When it's hard to the touch, wash and sand, period. And when in doubt, WEST says, be conservative: let it cure, then wash and sand.
• Peel ply. Lay release fabric over the wet epoxy when you're laminating or glassing. When it's cured, you peel the fabric and the blush comes with it, leaving a textured surface WEST says doesn't need sanding before the next layer.
• A blush-free hardener. WEST's 207 Special Clear won't blush or turn cloudy in humid conditions, but its minimum cure temperature is 60°F, so it still needs a warm shop. System Three sells SilverTip, Clear Coat and Cold Cure as blush-free; MAS and TotalBoat sell non-blushing systems too. TotalBoat and Interlux still say to wash any cured epoxy before you recoat, even if the label says no blush. Cheap insurance.
• Not for paint or varnish. The tacky shortcut only works epoxy-to-epoxy. Before paint, primer, varnish or gelcoat, WEST says let the epoxy cure fully, then wash, sand and follow the coating maker's directions.

MOAM's shop note: The cold-shop trick is to plan around the weather instead of fighting it. Mix and coat in the warmest part of the day, as System Three recommends, and keep the heat steady overnight so the temperature isn't falling while the coat cures. Warm the shop with a vented or electric heater, not a torpedo heater blowing combustion right at the hull. On a job like coating the inside of the dory's planking, put the second coat on while the first is still tacky and the third the same afternoon, so there's one wash at the end instead of three. And there's a bonus from Gougeon: if the first coat raised the grain, you can flatten those fuzzies back into the tacky epoxy with a plastic squeegee and recoat right away, no sanding.

Numbers and recommendations here come from WEST SYSTEM and Gougeon's Epoxyworks, System Three, MAS and Chesapeake Light Craft, TotalBoat and Interlux. Recoat windows and cure temperatures vary by product, so check the data sheet for the epoxy on your bench.

Sources: WEST SYSTEM, Surface Preparation, User Manual, 207 Special Clear Hardener. Epoxyworks, What is Amine Blush?, Jeff Wright, Let's Talk About Amine Blush (2024) and Tom Pawlak and Tim Atkinson, Minimizing Amine Blush (1994). System Three, Why did my epoxy blush? and Working in cool temperatures. MAS Epoxies, What Is Non-Blushing Epoxy?. Chesapeake Light Craft, Epoxy Tips and FAQ. TotalBoat, How to Remove Amine Blush. Interlux, What is amine blush?.

MOAM Out.

Tools for this tip

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• 3M Scotch-Brite 7447 general purpose hand pads, maroon, 6 x 9 in. (20-pack): the maroon pad WEST names by number for scrubbing blush off with clean water
• WEST SYSTEM 207-SA Special Clear Hardener, 0.66 pint (use with 105 resin, 3:1): WEST's blush-free hardener for clear coats over brightwork (minimum cure temperature 60°F)
• ThermoPro TP50 digital hygrometer / indoor thermometer: shop temperature and humidity at a glance before you mix
• Etekcity Lasergrip 774 infrared thermometer: checking the hull's surface temperature, so a cold hull doesn't sweat on a fresh coat
• The Gougeon Brothers on Boat Construction (book): the Gougeon brothers' book on coating and building with epoxy

Use whatever you already have in the shop; these are just the ones that fit this job.

Woodworking Tip of the Day: Dust Collection You'll Actually Use: Hoods, Shrouds and PPE

This is catching the MOAM's attention today….. the dust. Not the chips on the floor, the stuff you can't see. Right now on the Chamberlain Marblehead gunning dory I'm sanding cured epoxy, fairing compound, a little teak and some cedar, and every one of those makes a fine powder that hangs in the air long after the sander stops. I've been building boats and running jobs as a licensed contractor long enough to know the dust setup that works is the one you'll actually turn on every time. So here's a simple one: catch it at the tool, clean the air as a backup, wear the right mask the right way, and clean up without stirring it all back up.

Why it matters: NIOSH treats wood dust as a potential occupational carcinogen and recommends keeping it under 1 mg/m³ over a work shift. OSHA's legal limit is much looser (15 mg/m³ total dust, 5 mg/m³ respirable), and OSHA itself says many of its limits are outdated and points employers to the NIOSH number. Teak is on the ACGIH list as a suspected human carcinogen, and Western red cedar is a known respiratory sensitizer, with a tighter ACGIH limit of 0.5 mg/m³. California's health department lists cedar, oak and mahogany among woods known to cause asthma. Then there's epoxy. WEST SYSTEM says the sanding dust of partially cured epoxy is still reactive, and breathing it raises your risk of becoming sensitized. Once you're sensitized, even a little exposure can set you off. Fairing fillers aren't much of a hazard on their own, WEST says, but any nuisance dust makes existing lung trouble worse.

Materials

• A HEPA-filtered shop vac (built for HEPA, not just a shop vac with a HEPA cartridge stuck in it)
• A cyclone separator and a bucket or drum between the tool and the vac
• Sander with a dust port, hose and adapter to fit it; hook-and-loop discs with holes that line up with the pad
• A small hood or shroud (store-bought or a shop-made box from scrap plywood) for jobs the sander port can't catch
• A half-mask respirator with P100 filters (or a NIOSH-approved N95 for short jobs); organic vapor/P100 combination cartridges if you'll be using solvents
• Safety glasses with side shields marked Z87, and earmuffs or plugs

Tools

• Random-orbit sander, longboard or sanding block
• Ceiling-hung air cleaner (optional, as a backup)
• Spray bottle and a damp rag or mop for the last pass of cleanup

Steps: a dust setup you'll actually use

1. Catch it at the tool, first. Hook the sander's port straight to the vac hose, with the cyclone in between. Fine Woodworking tested Oneida's Dust Deputy cyclone with quarts of the finest sanding dust, and "not even a teaspoon" got into the vacuum. That keeps the vac filter from clogging, so your suction stays strong, and you're not beating a caked filter out in the yard. Line up the holes in the disc with the holes in the pad, or the port isn't pulling anything.
2. Make sure the vac is really HEPA. A HEPA filter catches 99.97% of particles at 0.3 micron, the size that's hardest to catch. EPA's warning is worth hearing: a shop vac with a HEPA cartridge dropped in isn't necessarily sealed, so dust can leak past the filter. Buy one designed to run with a HEPA filter.
3. Put the hood right where the dust comes off. Suction dies off fast. OSHA's ventilation manual says that at one duct diameter in front of a plain opening, capture velocity is about 10% of the velocity in the duct, and the source should be no more than 1-1/2 duct diameters from the hood. OSHA's example: a 6-in. duct, 9 in. max. By the same rule, a 2-1/2-in. vac hose has to be within about 3-3/4 in. of the work. Blowing air carries a long way; suction doesn't. So for scraping, hand-sanding fillets or working inside the hull, clamp the hood right up to the work, and baffle the sides with cardboard or plastic so a fan or an open door doesn't blow the dust past it.
4. Run the air cleaner as a backup, not a substitute. Fine Woodworking's 2010 test of five ceiling-hung air filters in a mock 400 sq. ft. shop found they did clear the finest dust (0.1 to 10 microns) in 20 minutes or less, about 15 minutes for the best. The same test concluded they don't keep the air at levels experts call safe; for that you need collection at the source. Turn it on while you work and leave it running after you quit.
5. Pick the right mask. For dust, you want a particulate filter: N95 means it catches at least 95% of particles, P100 at least 99.97%. N means not oil resistant, R is somewhat resistant, P is oil proof. WEST's minimum for epoxy, wood and filler dust is N95 or better. On a long sanding session I wear a half mask with P100 filters. Organic vapor cartridges are for vapors (solvent wipes, or epoxy in a closed-up space like inside the hull), and a plain OV cartridge does nothing for dust. If you need both, use a combination OV/P100 cartridge.
6. Check the seal every time you put it on. OSHA's user seal check: cover the exhalation valve and breathe out gently; you should feel slight pressure with no leaks at the edges. Then cover the cartridges and breathe in gently; the mask should pull in slightly and stay that way while you hold your breath for 10 seconds. That check doesn't replace a fit test, which is how you find the right model and size. And the hard truth for us old-timers: OSHA doesn't let employers put tight-fitting respirators on anyone with facial hair under the seal. A beard breaks the seal. That rule is written for tight-fitting masks, so if the beard stays, look at a loose-fitting powered (PAPR) hood instead.
7. Change filters on time. NIOSH says replace any particulate filter when it's damaged, dirty or noticeably harder to breathe through. Vapor cartridges are a different story: OSHA requires either an end-of-service-life indicator or a change schedule based on objective data, like the maker's service-life figures. Bag the cartridges between uses.
8. Eyes and ears, quick. OSHA requires eye protection with side protection where there are flying particles; look for Z87 on the frame. NIOSH's recommended noise limit is 85 dBA averaged over 8 hours, and 85 dBA is also OSHA's trigger for a hearing conservation program (90 dBA is OSHA's limit). Planers, routers and a shop vac all at once add up. Earmuffs hang right on the vac.
9. Sand epoxy only when it's fully cured. WEST says epoxy cures to a sandable solid fast, but full cure can take more than two weeks at room temperature (or a post-cure with heat). Wait several days before sanding fresh epoxy, wet sand when you can, and if you can't wait, gear up: mask, glasses and long sleeves. Wash up with soap and warm water after sanding.
10. Clean up with the vac, never the air hose or the broom. The UK's safety regulator (HSE) says it straight: never dry sweep or blow wood dust off with compressed air, because it just makes a dust cloud you breathe. WEST agrees: vacuum or mop, because less dust goes back in the air. Vacuum the boat, the bench, the floor and your clothes, then a damp wipe.

MOAM's shop note: The dust setup that works is the one that's quick to start. Keep the vac, cyclone and hose on one cart next to the boat, with the mask hanging on the handle in a bag and the earmuffs on the hose. Plug the sander into the vac's tool outlet if yours has one, so the vac starts when the sander does. If it takes five minutes to hook up, some Saturday you'll "just do a quick pass" without it, and that's the pass that gets you. And if your shop's like mine in late October, with the doors shut and the stove going, the air cleaner and the mask matter more, not less.

Numbers here come from NIOSH/CDC, OSHA, EPA, WEST SYSTEM, Fine Woodworking, the California Department of Public Health and the UK HSE. The 3-3/4 in. figure is my arithmetic from OSHA's 1-1/2-duct-diameter rule.

Sources: NIOSH/CDC, Filtering Facepiece Respirators, User Seal Check FAQ, Service Time Recommendations for P-Series Filters, Understand Noise Exposure; 42 CFR 84.170 (LII). OSHA, Wood Dust, PELs vs. RELs, 29 CFR 1910.134 and Appendix B-1, 29 CFR 1910.133, Occupational Noise Exposure, Technical Manual, Ventilation. EPA, What is a HEPA filter? and HEPA vacuums. WEST SYSTEM, Preventing Overexposure, Shop Hazards, Epoxy Safety. Fine Woodworking, Dust Deputy Cyclone and Eric Constans, Air Filters (July/Aug. 2010). California Dept. of Public Health, Wood Dust and Work-Related Asthma. UK HSE, Wood dust.

MOAM Out.

Tools for this tip

As an Amazon Associate I earn from qualifying purchases.

• Oneida Air Systems Dust Deputy DIY anti-static cyclone separator for wet/dry shop vacs: cyclone between the sander and the vac, so fine sanding dust lands in the bucket, not the filter
• 3M 6503QL Rugged Comfort Quick Latch half facepiece reusable respirator, large: half-mask respirator for long sanding sessions on epoxy, fairing compound and teak (seal check every time)
• 3M 2091 P100 particulate filters, 3 pairs: P100 filters for the half mask: at least 99.97% filtration, oil proof
• 3M 60921 organic vapor/P100 cartridge, 1 pair: combination organic vapor/P100 cartridges for solvent wipes and epoxy in a closed-up hull
• 3M PELTOR X4A over-the-head earmuffs, NRR 27 dB: earmuffs to hang on the vac cart for sanders, routers and planers

Use whatever you already have in the shop; these are just the ones that fit this job.