A Technique, not a Finish
In the last article I described shellac as an easy to use finish: easy to apply, easy to clean up, and easy to repair. In this article we’ll look at an elegant nature of shellac: French polishing.
According to Bob Flexner’s “Understanding Wood Finishing”, French polishing refers to a technique for applying shellac, not a finish in and of itself. Essentially you apply a very large number of thin coats of shellac using a pad, a wee bit of oil, and a lot of elbow grease. There’s no need to get too caught up in the ‘right’ way of doing it. Like anything in life, with ample practice your French polished pieces will look better and better, and you’ll work out a sequence of steps that suit you best.
Do keep in mind that while a French polished surface has a high water vapour resistance, it has relatively low abrasion resistance. So it’s best used for pieces that won’t get a lot of heavy use, or be subject to water or alcohol spills.
What You Need
French polishing doesn’t require much in the way of materials. You’ll need some freshly made shellac (begin with a 1-pound cut which is thinner and easier to apply; later you can use a 2-pound cut if you want to speed up your finishing); a rubbing pad, and some mineral oil (which keeps the rubbing pad from sticking to the freshly applied shellac). If you’re using pre-mixed shellac remember that it’s likely a 3-pound cut, so you’ll want to thin it by adding some denatured alcohol. As an alternative to denatured alcohol you can use 99% isopropyl (available at most pharmacies) or denatured ethanol (typically a mixture of 85% ethanol and 15% methanol). Methyl hydrate should be avoided as it’s highly toxic. Regardless of the thinner you use, it’s important to wear a respirator (preferably a full-face) and nitrile gloves. And remember not to flush any solvent or thinner down the drain – call your local recycling center to find out where to dispose of it safely.)
Because you only need to apply a bit of shellac at a time, things go easier if you pour some shellac into a squeeze bottle (old mustard bottles work great; it’s also a convenient way to dispense the alcohol). To make a rubbing pad you’ll need some lint-free cotton, or linen, for the ‘cover’ (about 8″ by 8″) and some cotton, wool, or cheesecloth for the ‘core’. Make a wad about the size of a tennis ball with the core material, and then wrap the cover over it, ensuring that the bottom of your pad is smooth. Before using a new pad you can ‘condition’ it by delivering a couple of good squirts of shellac onto the core of the pad. Store the pad in a jar or zip lock bag when not in use, as you don’t want to let it completely dry out. When the cover material gets dirty or torn just replace it; the core will last for ages. You’ll be exerting a lot of pressure when applying the shellac, so it’s a good idea to secure your work piece to your work surface (I used padded battens).
Fill the Pores
For wood with small pores, such as maple or cherry, you go straight to work with the shellac. For large pored woods, such as oak or walnut, the finish will look smoother and glossier if you fill the pores. The easiest and quickest way to fill the pores is to brush on consecutive coats of shellac, sanding between coats, until the pores are filled. If you’re a purist and want to fill the pores the old fashioned way, you can read about it in Flexner’s book. On darker woods, like cherry, I lay a thin coat of boiled linseed oil on the surface before filling the pores, to increase the depth of the finish.
When you are ready to apply the shellac, squirt enough shellac onto the pad to dampen it (damp, but not ‘sodden’). This process is called ‘charging your pad’. Then give it the traditional ‘French kiss’ (smack the pad against the palm of your hand) and you’re ready to go.
The first step is called ‘bodying’. Three things to keep in mind at this stage: 1) keep the pad moving. If you let it sit on the surface it will stick; 2) once you’ve padded over an area, wait until it’s dry before going back over. If you don’t do this, your pad will stick; and 3) begin with light pressure then increase pressure as you polish. Good lighting is important so that you can see whether you’re applying the shellac consistently across the whole work surface.
Begin your bodying by pressing the pad on the work surface and simultaneously begin moving in circles or figure ‘8s’. No need to go too fast, just keep your pad moving. As you start to feel some resistance when moving the pad, apply more downward pressure. When you start to feel a lot of resistance, it’s time to lift the pad off the surface. Add another squirt of shellac, plus a drop of mineral oil, which you’ll add, each time you recharge your pad with shellac from now on. Give it the French kiss, then rub on. Once you begin adding the mineral oil, you will begin to notice streaks (called ‘clouds’) of oil on the surface. You will remove those clouds later.
Remember that shellac dries pretty quickly, so by the time you’ve applied one coat it’s dry enough for the second coat. The idea is to lay down as may coats as it takes to make the surface look smooth and level. And don’t forget those edges. You don’t have to complete the polishing all at one go. Try applying six or seven coats then let it dry overnight. That will give the shellac time to cure. Lay on another six or seven coats the next day, and so on. You’ve completed this stage when you’ve built up a mirror like finish on the surface.
The next step is called ‘spiriting’ or ‘clearing’. It consists of removing the oil that’s still left on the surface. It’s a good idea to let the shellac cure for a few days before you clear off the oil. The traditional way is to use alcohol. Make a new polishing pad and charge it with a few drops of alcohol. Use the pad in a sweeping motion across the wood surface: begin on one side of the surface like an airplane coming in for a landing, sweep across the surface, then lift it off at the other edge, like a plane taking off. Continue until you have a glossy sheen. Be careful not to damage the shellac by rubbing too hard. A quicker and easier way to remove the oil is simply to wipe the surface with naphtha (camp stove fuel).
The final step is to apply a wax and buff it out.
French polishing isn’t for everyone. But, like Alexander Keith’s Pale Ale: people who like it, like it a lot!
The process of French polishing is like any recipe: it has as many variations as the people who use it. For another variation of French polishing, see Canadian Woodworking Magazine: August 1999 and October 1999.
You can get shellac flakes or pre-mixed shellac from Wood Essence, www.woodessence.com or 306-955-8775