I recently "re-discovered" a finish for my work that is easy and versatile. I
was looking for something that was easy to apply, went over various
stains, colors, and woods, and could be coated multiple times
in one day. I had been reading an article on shellac in a woodworking
magazine and realized I had forgotten about the properties of
shellac and how to work with it. Shellac is an excellent finish
for carvings that can be sanded smooth when I want a clear, silky
finish.
First, shellac is an excretion of the Lac insect in India and other close-by regions of the eastern world. It is sold either as dry flakes or premixed with alcohol. Usually in hardware stores and similar places you will only be able to get pre-mixed, 3 lb cut shellac in one or two grades. If you buy from Garrett Wade and similar vendors, you can find shellac in dry flake form in several grades. The grades range from dark to blonde, with blonde being nearly clear and the purest. The dark has more impurities in it that have not been strained out and so you can get anything from a very clear coat to an antique look without any additional work. The cut referred to is the number of pounds of shellac flakes dissolved in a gallon of alcohol. 3 pound cut is the usual pre-mixed variety but with the addition of more alcohol, you can reduce the shellac to a thin coat equivalent to a 1 or 2 pound cut. Each cut has it's use and application for us.
You need to decide if you want to have the finish clear or allow the shellac to add an orange-brown color and choose your shellac grade accordingly. If your wood is unfinished or already stained, you should brush on a wash coat of very thin 1 lb cut shellac. (To achieve this thin mix, add 2 parts alcohol to 1 part 3lb cut shellac) Brush this on and let dry. Sand your carving with a 220 grit paper to de-wisker the wood once dry, then go over the carving again with the thin shellac mix. Sand again with a finer grit paper and then apply 2-3 coats of shellac, allowing each to dry. Sand this again as fine as you want/care to. You can, depending on the open or closed grain of the wood, develop a satin smooth finish, based on how many coats of varnish you care to apply. This application of shellac and then sanding will eventually fill even butternut and other open pore woods. Tight pore woods like cherry and maple will seal and be satin smooth in far fewer coats. Once the surface is the way you want it, apply a final coat of shellac, either padded on with a clean cotton cloth, or brushed on and then carefully polished up to final finish with rubbing compounds such as auto rubbing compound down to as fine as rottenstone for a high gloss shine.
Shellac will bond with each layer below it, so brush it on quickly and evenly and don't spend a lot of time re-coating the same area as you will be working with the softened finish under the coat you are applying. Being alcohol based, you should use a good grade of Ethanol alcohol as other alcohols may not work as well, or be more toxic to you as you use them. Behlens is one brand of shellac flakes and alcohol and has their own variety of alcohol for cutting the shellac and is a good choice if you are uncertain what to use. Garrett Wade sells Behlens products and their catalog offers good advice on the varieties of shellac and solvents. Other woodworking supply catalogs also carry shellac products as well.
Shellac offers the advantage of being able to be tinted with alcohol based analine dyes and stains or can be applied over water- or oil-based stains already on the wood that have dried completely. Once you have the wood sealed with the wash coats of shellac, you can tint the 3 lb cut with whatever color you want to create a deep, vibrant look. If the finish gets too dark for you, you can remove it carefully with rags and alcohol and the original wood is still the same color. This trick can be used to blend lighter sap wood with darker heart wood on a carving. Woods such as walnut tend to have very noticeable color changes in the wood and you can minimize that difference if you so desire.
Shellac does not work with foam brushes, but you can use a good natural bristle brush and clean it in alcohol with each use. After cleaning in solvent, I work waterless citrus-based hand cleaner deeply into the bristles and give the brush a final washout with warm water.
Shellac is a good barrier finish between oil and varnish, or even works under spray lacquer if necessary, I believe. Always test your finishes and stains and colorants on a scrap piece of the same wood as your carving to insure compatibility. With this in mind, you can use an oil-based stain on the wood, let it dry, give it a coat of shellac, and later use water-based poly over it for a final finish. although I would tend to stick with just shellac after than. Conversely, you can apply a wash coat of shellac over uncolored wood, and then apply a dark stain over the shellac to allow a more uniform color. Once dry, finish upwith shellac. This keeps the end grain from becoming darkly stained and allows you to get an even color.
Shellac has a number of good points: it brushes and sprays well, it can be very clear or tinted to any shade you like, it resists humidity well, scratches can be repaired quickly and easily, and it is fairly safe and environmentally friendly. On the down side, it does not resist water well, or heat, or alcohol and other chemicals; however, most of our carvings are unlikely to be placed in a position where that is a problem.
This is far from a complete review of shellac, but I would recommend checking with periodicals like Wood magazine, Fine Woodworking, and Shopsmith for articles detailing how to use shellac. Past issues are often available in libraries or from the publisher. There are also several good books out devoted entirely to finishes that include good information on shellac, I highly recommend them!