Shellac is a great tool for finishers and restorers alike because it has a myriad number of uses for furniture. This short blog will aim to quickly familiarize you with its applications in a professional restoration shop setting. That being said, this is merely an academic summation, and I would strongly recommend you go out, buy your own shellac, and practice on some test pieces of 400 sanded grit boards. Experience is the best teacher.
Shellac is a natural resin produced by an arboreal insect called the Lac Bug. Today Lac Bugs are farmed on trees in both India and Indonesia, and their resin is used for: pill coatings in the pharmacology industry, an additive mixed into candy and edible products, and it is refined into dry flakes for wood finishing. In reference to its chemistry, Shellac liquid and shellac flakes are both soluble in an alcohol solvent. They are not compatible with water, lacquer thinner, or direct mixing with oil or organic petroleum solvents.
Traditionally, restorers sourced bags of refined flakes and melted them down ahead of time before restoring a piece of furniture. Melted flakes gives a restorer control of the shellac viscosity, working properties, and some interesting color choices. For example, flakes can be purchased in a variety of states of refinement with different wax contents. The higher the wax content, the easier is can be applied by hand because the shellac is more malleable and can be burnished more easier via French polishing. This makes sense, because more wax means less friction during application.
French Polishing is the art form of applying shellac resin by hand on furniture. It’s heyday was around the 1820’s in Europe, when pieces were being refinished and French polished to bring out the natural figure and chatoyance inherent in wood grain. This method of finishing was popular until the 1940’s, when nitrocellulose lacquer was developed, and then became the industry standard for the next half a century. As a finish Shellac is not very durable. However, it is very repairable, quite beautiful, and most importantly it’s chemically stable. When I say chemically stable I mean it can be left alone with very little care for over 100 years.
In a professional setting I like to employ 4-5 different kinds of shellac in my finishing arsenal. For rich color and quality during French polishing I use Blonde flakes from BT@C, which can be purchased online from woodcraft.com. If I want to create a slight ambering effect to mimic a patina, or cover over a color matched area to build a topcoat quickly, I like to use Garnet flakes. Garnet flakes have undergone the least amount of chemical refinement and so they are darker, and have a higher wax content. This allows me to French polish an area and build much quicker then by using Blonde alone.
Two other useful shellac products I always keep in inventory are Shellac clear and Seal coat. These are both produced by Zinssner, are premelted in a can, and can be purchased at a local Home Depot. They are go to staples, the most affordable and also have several uses each. Shellac clear has a high wax content which makes is easier to apply and build quickly. However, as such, it’s higher wax content acts like mixed solids in a lacquer that disperse light. This creates a softer more satin sheen to a French polish. Therefore, if you know a head of time that a client wants a satin sheen finish as an end product, this kind of shellac is a great tool for getting there quickly. Seal coat is a highly refined blonde shellac in a can; ranging from a pint to a full gallon in volume. It has a great color, and works quite well in a spray booth setting to spray color; or used as a topcoat to lock in a color underneath it. Typically I stay away from it when French polishing because it has a very low wax content, so it’s more physical work to apply it and get it down smoothly and uniformly on a piece of furniture. It drys harder and looks great, but I reserve it for the spray booth where it can be more functional. Seal coat’s low wax content is ideal for this application because it can then be used in conjunction with other finishes on top of it.
Hopefully this small write up will encourage you to get out there, take some small risks, and go play with these products to learn about them yourself. Experience as your teacher will tell you which shellac you like to use in your own shop. Also, for a great source of information, I would highly recommend reading Jeff Jewitt’s book: The Complete Illustrated Guide to finishing. It’s like finishing bible for this esoteric artform, and has soo much good information that it might blow your mind. Additionally, should you get the opportunity to visit the Winterthur Furniture Museum in Delaware, I would highly recommend closely inspecting the Americana period pieces. Specifically check out their collection of desks, high boys, and chests of drawers. Not only are the pieces masterfully made, their traditional finishes are still going strong.