Working with Wipe-OnsComments (0)
This article is from Issue 23 of Woodcraft Magazine.
Unless you own a HVLP system and have outfitted your shop with a spray booth, you probably rely on brush-ons and wipe-ons for most of your finishing. And of these two, you may prefer the latter for a few very good reasons. Wipe-ons, specifically, wiping varnishes are perfect for small shops because they apply easily, dry quickly, provide lasting protection, and make wood look terrific. (See “What’s a Wipe-On?” below.) For Scott Phillips’ Trestle Table and Bench on page 20, a wipe-on varnish proved ideal because it let Scott finish the tabletop, seat, and rails while cutting the base parts on the other side of his shop.
That said, quick and easy doesn’t mean foolproof. To help you achieve the best possible finish and avoid common goofs, we’ll show you a five-step process that involves sealing, building, and fine-tuning the finish to get the look and protection you want.
Before you crack open a can, check out the “Tools and Materials That Do the Job” on the next page (and the Convenience-Plus Buying Guide on page 36). Even if you don’t use all these items on your next project, you’ll want to keep this basic wipe-on tool kit handy so that you can complete a finish with a minimum of starts and stops.
What’s a Wipe-On? Wiping varnishes, oils & blends
The term “wipe-on” describes an application process. Technically such finishes include varnishes, oils, and oil/varnish combos. Oils are fine when you want a thin, easily renewable finish, but for this story, you’ll use a wiping varnish. The varnish establishes a scratch-, water-, and stain-resistant film that can be built up in coats, and then rubbed out to the desired sheen. How can you tell?
Here’s a simple test: place a few drips of finish on a piece of glass or paint lid and give it a day or two to cure. If it cures hard and smooth, (un like an oil or oil/varnish blend) it’s a varnish.
Prep work: sand smarter, not harder
In truth, most of us sand too much. With a thicker film-forming finish, such as a brush-on polyurethane, sanding up to 180 grit is sufficient. Because wipe-ons leave a thinner film, consider sanding up to 220 grit just to play it safe. Sanding with any finer grit won’t help.
How you sand can make a difference. To prep the surface properly, follow power-sanding by hand-sanding lightly with 220 grit. Sand with the grain to erase machine-made swirls or squiggles. To avoid creating finger divots, use a sanding block on larger flat areas. Fold the paper to stiffen it slightly when sanding tighter spots.
Wipe-ons deal with dust better than any other finish, but there’s no point in pushing your luck. Always remove dust and grit after sanding. Use a vacuum, tack cloth, or brush to clean the surfaces. (Avoid a compressed air blow-off, as it tends to suspend super-fine dust in the air for days.)
Brush on a base coat
With a base (sealer) coat, your goal is to give the wood as much finish as it wants. Spending a little more time and finish now makes it easier to build to the desired finish later.
Using a foam or cheap bristle brush, lay on a generous coat of finish, as shown in Photo A. Continue applying finish to the thirsty spots for about 20 minutes or until the surface maintains a fairly even “wet-but-not-puddled” look. (Don’t wipe off the excess; most will be absorbed by the wood, and the rest will be sanded off in the next step.) Now allow the finish time to dry; eight hours works; overnight is even better.
Sand once, then only when you must
At this point your finish will not only look blotchy, but also may feel rough due to loose wood fibers lifted by the first coat of finish. Using a sanding block and 320-grit paper, scuff-sand the surface, as shown in Photo B. Scott uses Norton’s 3X paper because it cuts longer than standard paper and is stearated to resist clogs. (See the Buying Guide.)
Don’t sand too much. Two or three light passes should cut off any whiskers or dust nibs. Aim for a surface that feels smooth; minor finish imperfections will even out after one or two topcoats. After sanding, wipe off the dust and stearate residue with a rag dampened in mineral spirits. (The rag not only cuts down on airborne dust, it also gives you an early look at what the final surface will look like.)
From here on, the 320-grit sanding block can usually stay planted on your shelf. Of course, accidents happen. If a tool takes a nosedive onto your piece in mid-finish, or if a dust chunk plants itself in a coat, you may need to feather out the damage. Just remember that the finish is thin; if you get carried away, you’ll sand through days of work.
Padding on the finish
The directions provided by most wipe-ons can mislead you. Wiping on, waiting, then wiping off the excess winds up putting more finish on the rag than your project. If you don’t wait long enough, you’ll wipe off the finish you’re trying to apply. Wait too long, and the rag sticks to your work. The trick: build up a nice looking film faster by treating wipe-ons like super-forgiving brush-ons. As an added benefit, the cheapest, most controllable applicator is waiting for you in the rag bag. (If you run out of old T-shirts or cotton bedsheets, see the Buying Guide.)
Bunch the rag into a tight ball, or fold it into a thick square pad, as shown in Photo C. Your goal is to make a smooth applicator that absorbs a decent amount of finish and releases it onto the surface in a controlled, smooth manner.
Wipe-ons give you plenty of application time, but they will get tacky, so you want to work fairly quickly. Dip the pad into your finish and then transfer it onto your surface. As when brushing on the base coat, apply enough finish to create a glossy-wet surface without puddles.
Immediately after “padding” on the finish, wipe away pad marks and puddles by making light touch-and-go passes as shown in Photo C. To do this, first dampen the pad so that it won’t pull finish off the surface. Using long, even strokes, land the pad on the surface, wipe the surface with a long, even motion, then lift the pad at the end of the stroke. Any remaining streaks should quickly level out, but don’t worry if they don’t. Later topcoats will fix minor inconsistencies.
The regs on reapplication
The hardest part of this step is knowing when to walk away. If you see a light spot halfway through, or if the pad leaves marks, use a little more varnish, but your best bet is to put the rag down and give the surface 4-6 hours to dry. Decide then if the blemish can be blended in with additional coats, or if you need to feather it out with 320 grit.
The advantage to wipe-ons is that they dry fast. If you start early, you can apply two or three light coats in a day. (If you need to sand, you may want to give the surface an extra day to cure to ensure that it doesn't clog your sandpaper.)
Exact coat counts are but a suggestion. Film thickness really depends on the finish brand, how much you lay on with each coat, minus what you sand off. For most projects, three to five coats is plenty, but for extra protection, apply 10 coats or more. (Depending on how well you hit the application windows, the process can take from three days to a week.)
Tools and materials that do the job
A few items can help you fix minor imperfections and finish faster. You won’t use them every time, but they’re good to keep in your finishing arsenal, just in case.
Seal-A-Cell and Foam Brushes
Brush on a generous base coat to seal wood. You can use a wiping varnish, but the oil in Seal-A-Cell adds more color than competing wipe-ons.
Arm-R-Seal and Applicator Pad
The convenience and control of a cotton rag is tough to beat. To avoid contaminating the can with dust, pour the finish into a smaller container and work from it.
320-Grit Sandpaper and Sanding Block
Scuff-sand the base coat as little as possible. Laying on an extra coat is faster than sanding through and starting from scratch.
Steel Wool and 600-Grit Sandpaper
Sandpaper levels the finish; steel wool evens out the sheen, but use both with caution. If you burn through, you’ll need to re-wipe and wait a week before rubbing out.
Brown Paper Bag and Wax
These low-grit and no-grit solutions hide scratches, bring out the shine, to create a super-smooth surface. They're worth trying before using coarser abrasives.
Gels: Goof-proof, but slower-going
Gel varnishes originate from the same resins as wiping varnishes, but contain less solvent and/or an extra agent to make them mayonnaise-thick. This consistency makes them less messy (it’s tough to make them drip, even if you accidentally tip the can). Ease of use depends on the size of project, and the sheen your desire.
The wipe-on, wipe-off gel application process produces a flawless finish that you can recoat in 2-4 hours. This makes gels great when racing to finish small- to medium-sized projects… if you’re looking for thin satin finish. However, because gels don’t self-level, you can’t build a film by leaving it on thick. And the lower-solvent content means that they dry quickly, so you need to finish large surfaces in sections before it hardens beyond use and grabs your rag.
In side-by-side shop tests, it took five coats of General Finishes Gel Topcoat (#826990) to produce a sheen roughly equal (but slightly lighter in color) to a sample finished with one coat of Seal-A-Cell and two coats of Arm-R-Seal. While the gel-finished board looked good enough to leave the shop, the other required a little steel wool and wax.
I prefer the protective film and flexibility afforded by wetter wipe-ons, but use gels when I don’t have the time or simply don’t want to fine-tune a finish. –JH-W
Finishing the finish
Like full-strength varnish, wipe-ons can be abraded to even out the gloss, or rubbed to build up a sheen. The amount of work left after padding on finish depends on the finish you desire. Less is best. In some cases, you can avoid using the wet-dry sandpaper and go directly to wax.
If the surface looks good, you’re almost done. Give the finish time to cure, a week is good; two weeks, better. Next, burnish the surface with a brown paper bag. There is just enough grit in the paper to smooth over nibs, but not enough to change the sheen, unless you rub really hard. From here, decide if you want to down-shift to steel wool, or wrap things up with wax.
Use steel wool if you need a little more “cut,” or if you want a medium-luster finish. Unfold a pad of 0000 steel wool and lightly rub the surface. Keep checking it under a raking light. When you get an even dullness, wipe off the steel wool crumbs, and then finish with wax.
Leveling bigger bumps, and/or achieving a super smooth finished surface, requires a small step back. Give your last coat of finish a day or two to dry, and then use a sanding block and 600-grit sandpaper to level the topcoat (Photo D). Lubricate the paper to prevent clogs that might create irregular scratches. Wipe off the residue to check your work. You can use a smaller block to sand any remaining shiny spots.
Once the surface is smooth and level, you can try wooling and waxing, but for a super-smooth finish, apply one thin coat of wiping varnish or gel. This coat will fill the scratches and dry before dust has a chance to stick. Give that spit coat a week to cure, and then finish with wax.
Wax on, wax off
A wax topcoat is only a few molecules thick, but it provides decent protection against water and food stains. Most importantly, this easily renewable topcoat hides tiny scratches and makes the surface silky smooth. To apply, wipe on a thin coat of clear paste wax, and then buff it off as soon as it hazes.
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