Rediscover the Joys of Shellac
My friend Bill called the other day with a problem. He had applied more than a half-dozen coats of gel polyurethane on a cherry table he'd just made and now, a week before the table was to become a wedding gift, the sheen was uneven.
Two distinct patches on the top had a higher gloss than the areas around them. Given Bill's usual attention to detail, this wasn't going to work. What's up? he wondered.
Rubbing out the finish with a very fine abrasive fixed the sheen problem, or nearly so. But it made me think about the virtues of a very old finish that seems lost in the shuffle of solvent and water-based formulations.
Shellac Is Simple and Reversible
Compared to complicated chemical brews like polyurethane, conversion varnishes, and water-based acrylics, there's something charmingly old school about shellac. It was the finish of choice a century ago for furniture, casework, and trim, and it's too good to be ignored today.
Shellac comes from the secretions of the lac bug, which lives in the forests of India and Thailand. It's collected by hand, refined, and sold in flake and button form.
There are many things to like about shellac; its benign chemistry (children can chew on shellac-finished toys without any ill effect), its durability, its clarity and ease of use, the speed at which it dries, and its versatility as a sealer and finish.
It's also reversible, meaning that it's easy to remove without doing any damage to the underlying surface.
Make Your Own: It's Better Than What Comes in a Can
Although you can buy premixed cans of shellac at the hardware store, you're better off making your own from shellac flakes and denatured alcohol. The stuff in cans has a long shelf life, but it also contains wax, which some finishers insist can cause adhesion problems when a different top coat is applied over it.
You can buy shellac in many forms, ranging from dark seed lac to super blonde, and in waxed and de-waxed versions. Blonde shellac has an unusual clarity that gives figured wood great visual depth.
To make it, put some flakes into a jar, add denatured alcohol and let the flakes dissolve. This stock is thinned with more alcohol until you've got the consistency you want. A "two-pound" cut (mixed in the proportions of two pounds of flakes per gallon of alcohol) makes a good general purpose finish.
Shellac flakes are sold through woodworking supply houses and on the Internet. If you want to learn more, try www.shellac.net.
Shellac isn't as bullet proof as polyurethane, but it's much tougher than it gets credit for. And unlike many finishes that are very difficult to remove once they've cured, shellac can always be dissolved with alcohol.
That's its Achilles' heel, too. Shellac isn't the best choice for a cocktail cart. But for furniture and casework, it's worth trying and, as Bill would have discovered, very easy to rub out to a beautifully even luster.
See a full list of Scott's how-to columns at Old House Questions and Answers.