Understanding Wipe-On Finishes
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Understanding Wipe-on Finishes he moment of truth for many projects comes T and smooth, you have a thinned, or true, wiping long after the shop is cleaned, the tools are put varnish. If the puddle dries wrinkled and soft, itʼs away and the work is sanded. Applying a finish an oil/varnish blend. stops many woodworkers dead in their tracks. Why is it important to know what kind of wip- Finishing is the chore almost all woodworkers ing finish you have? When it comes to protecting fear most because it has the greatest potential the wood, varnish wins because it dries hard. for spoiling the project. So itʼs only natural that The reason has to do with the way the products woodworkers would seek a risk-free finish. For are manufactured. A typical oil-based varnish is this reason, many choose a finish thatʼs wiped on. made by cooking alkyd resins with an oil (usually Finishing manufacturers have capitalized on this modified soybean oil). To make a wiping varnish, fear and have developed rag-on finishes – thatʼs the finish is simply thinned with paint thinner or the good news about many products today. mineral spirits. Oil/varnish blends go further, The bad news is that the finishes you find on adding more oil and thereby further reducing the the shelves at your home centers have similar quantity of varnish in the finish. names but arenʼt alike – and you canʼt figure out Still confused about what to do? Well, the what each one does by simply reading the can. sure-fire way to get what you want is to make This is what they all have in common: You your own wiping varnish. Itʼs easy. Buy a can of wipe them on, allow them to dry and then add oil-based varnish and thin it with paint thinner or more coats for additional protection. mineral spirits. Add either one part thinner to four But the real questions for us are: Just how parts varnish or, for a slightly thinner mix, one many coats do you need? And how much pro- part thinner to three parts varnish. If you make tection can you expect? To get these answers your own, select varnish with the sheen you prefer. you first have to have some knowledge of the Usually a mid-level sheen such as semi-gloss or finishing productʼs contents. Because the actual satin is best for furniture finishing. contents arenʼt listed on most products and the With your finish mixed, actually applying it names canʼt always be trusted, you can do a simple is mostly foolproof. First, make sure you have test at home to get some answers. adequately sanded the project. I prefer to use a With the exception of pure oil finishes (such random-orbit sander for flat surfaces. Start with as boiled linseed oil) most wiping finishes are #120-grit sandpaper. Sand out all the imperfec- either a varnish thatʼs thinned with a reducer (like tions: scratches and marks left by your tools and paint thinner or mineral spirits) or a combination glue. Then move progressively through finer sand- of oil and varnish. To see which one you have, paper grits: #150, #180 and #220. Brush or blow pour a small amount on a hard surface like glass off the dust between each grit. Remove as much or metal to form a small puddle. Let the puddle dust as possible before applying the finish. dry for a couple of days. If the puddle dries hard To apply the wiping varnish, use a clean cloth rag. T-shirt material works well, rivaling cotton cheesecloth, which is touted as being especially lint-free. You can purchase cotton cheesecloth at Story by Steve Shanesy, editor & publisher most home centers or paint stores. Wipe on the finish equally on all surfaces. The oil-based pigmented stain, you need to be careful. surface should look wet but it should not pool. The application of a wiping varnish using a rag This is especially true for the first coat, which could cause the stain to redissolve and smear. soaks into the wood. The subsequent coats donʼt Instead, lightly brush on two coats and donʼt brush penetrate and will look wetter. over areas with wet finish. After the second coat After the first coat has dried, lightly sand using dries, sand the wood to smooth the surface. Be either #320- or #360-grit coated sandpaper. The sure to sand lightly, however, especially near coating helps prevent the finish dust from clog- edges or on moulding details. These areas are ging the sandpaper. Norton Abrasiveʼs 3X brand susceptible to sanding through the finish and and 3Mʼs Tri-M-Ite are good options. This light When a thinned or wiping varnish dries on a non- then through the stain color, which will expose sanding should substantially smooth the finish porous substance, such as this piece of glass, it is the natural color of the wood. WM smooth and hard (left). Oil/varnish blends, on the surface. Wipe clean all the dust and recoat. In all, other hand, will cure soft and wrinkly on a non-po- three to four coats should be enough. rous surface (right). If you colored your project beforehand with an Contact the author at 513-531-2690 ext. 1238 or steve. [email protected]. 30 O WOODWORKING MAGAZINE Spring 2004 A Finishing Experiment e conducted a couple of simple experi- Wments with five wiping varnishes readily available from local home centers, plus our own homemade version and a full-strength varnish. Two products (Minwax and General Finishes Arm-R-Seal) are wiping polyure- thanes, which technically are varnishes but use urethane resins instead of alkyd resins. In the first experiment, we applied all the finishes to a walnut plank and compared the looks, as seen in the photo. We applied four coats, with light sanding after the first coat. For the second experiment, we placed equal amounts of the finishes (measured to the thousandth of a pound) in identical open containers and allowed the finish to evapo- rate, leaving the dried resin on the bottom. We then weighed the dried material. The result told us how much of each finish was sol- ids (which protect the wood) and how much was solvent (a carrier of resins that evaporates, leaving a dry, solid film finish on the wood ). PARRISH AL PHOTO BY The dried samples also gave us a better under- We tested seven wiping varnishes to see how they performed when rubbed on a walnut plank, shown standing of the hardness, flexibility, clarity and here. At the bottom are the dried films that remained when the liquid dried in the open containers. color of each finish when cured. As a reference, these characteristics can be viewed in a variety of ways. For example, an clearest with a mild yellow color – Arm-R-Seal O Formby’s Tung Oil produced one of the amber color in the dried film could be good if was a bit more orange. Arm-R-Seal’s film was most pleasing-looking finishes of the group. you want to add warmth to the look of your less flexible and harder. In measured charac- While it tied with Sealacell for the lowest solids wood. But a finish with little color may be pre- teristics, it had the highest percent of solids rating (29 percent), the film on the wood had ferred if you’re finishing a white wood such as (34 percent) of all the commercial products a more natural look. The dried film was yel- maple or ash. Hardness is a good attribute but except unthinned regular varnish. Arm-R-Seal lowish and flexible, yet tough. It was almost as it’s a trade-off with flexibility, an equally im- is considered a sealing coat, with Sealacell clear as the two General Finishes products. portant attribute that allows the finish film to used as a finishing top coat. Sealacell tied for O Waterlox, as previously noted, appeared move with the wood during seasonal expan- the lowest percent of solids (29 percent). as a dried film more orange and far less clear. sion/contraction cycles. O The Minwax Wipe-On Poly sample dried The dried sample actually was translucent and Of the seven samples tested, only one dried to a tough, brittle, clear film that was amber had a solids content of 31.5 percent. On the notably differently – Waterlox. All of the other in color. On the board, it produced an attrac- board, it appeared duller and slightly less clear products showed minor differences. tive protective film without appearing thick than any other product. The dried film was O General Finishes Arm-R-Seal and Sealacell or plastic-looking. It was less clear than other softer and more flexible than the other prod- looked about the same. Both were among the products and had a 32 percent solids content. ucts, making us wonder about its suitability for use in demanding circumstances such as tabletops or countertops. O The unthinned varnish, a McCloskey Look through the shelves at your local home center and you’ll see many products with simi- product, and our home-brew wiping varnish lar names. But how do you know what the products really are? Our list will help. made from it produced clear, flexible yellow- Common Wiping Varnishes Common Oil/Varnish Blends tinted films that were as tough as any in the group. As expected, the varnish directly from • Daly’s ProFin • Behlen Danish Oil the can had the highest solids content at 39.5 • Formby’s Tung Oil Finish • Behlen Salad Bowl Finish percent.