Of all the many wood finishes available, woodworkers love shellac for its many benefits. The finish is non-toxic; it can be used as a sealer before applying a stain; it can be tinted, and it's easy to repair if damaged. Because shellac also dries quickly when applied to wood, it takes some practice to learn how to properly apply the finish.
How Shellac Is Made
Shellac has a unique manufacturing process. It's derived from a resin secreted by insects native to forests in Thailand and India. The secretion is scraped from the bark of trees and then processed to form small, light-brown, or orange flakes. The flakes are mixed with alcohol to create a finish.
How to Buy Shellac
You'll find shellac premixed in home improvement centers and ready for immediate application. Premixed shellac is perfect for beginners. But, you can also buy shellac in "cuts" to create homemade shellac mixtures.
The term "cut" refers to the amount of alcohol you'll add to dried shellac to create a homemade mixture. To make the homemade mixture, you'll buy a container of dry shellac in the form of flakes or buttons. The dry shellac will be "cut," or mixed with a ratio of denatured alcohol. Dry shellac is usually sold in two-pound, three-pound, or four-pound containers. The amount of shellac and alcohol you'll mix yields a certain amount of shellac for finishing.
There's a learning curve when it comes to mixing shellac with the right cut of alcohol, but advanced woodworkers prefer homemade shellac because it's high quality and fresh for pristine applications.
Brushing on Shellac
You can apply premixed or homemade shellac by brushing it on or padding it on to wood. Brushing is the more common method of applying shellac.
Brushing on shellac requires a fine, natural or china-bristle brush. Use a two or three-pound cut of shellac and apply generously with long, smooth strokes. Since shellac dries quickly, be careful to avoid drips or blotchy areas when applying because unlike other finishes, you will likely not have time to over-brush to eliminate the blemish.
Many woodworkers like to use a combination of brushing and padding. Apply the shellac with a brush, then immediately smooth it out with a piece of muslin. Use long strokes moving with the grain of the stock.
Padding on Shellac
Padding on shellac is a bit more involved. To create the pad that you'll use for applying shellac, find a clean white sock and cut a clean piece of medium-weight cotton muslin, or a lint-free polishing cloth, into a 12-inch square.
Before using padding to apply shellac, place the finish into a squeeze bottle with a fine tip for easy use. Squeeze a liberal amount of shellac into a sock, which acts as a reservoir. Wrap the piece of muslin around the sock, holding the edges of the fabric behind the sock. Begin applying by lightly squeezing the pad to allow a small amount of shellac to seep through the muslin.
Add a small amount of lubricant, such as mineral oil, on the pad before application. Mineral oil will not affect the final color or finish of your wood. If your pad seems a bit sticky as you're applying shellac, keep a small bowl with a little bit of mineral oil handy for light dipping.
To begin applying shellac, quickly ease the pad on and off the surface to avoid any blotchy spots. Avoid placing the pad directly down onto the wood and rubbing. Work the pad in gentle, irregular patterns rather than only going with the grain. This method ensures the surface is thoroughly covered with shellac. As you need more shellac, simply squeeze a bit more onto the pad.
Completing the Shellac Finish
After the first coat of shellac completely dries, lightly sand the surface with 400-grit sandpaper. Wipe off the white residue with a soft tack cloth, and apply a second coat. Repeat the process until you've applied the desired number of coats. About three to four layers of shellac will give you the beautiful, even finish you're after.
Shellac can result in a high-gloss finish. A mirror-like glossy shellac finish is achieved by French polishing. If you prefer a less glossy, satin finish, buff out the final coat with 0000 steel wool and a non-silicon based paste wax. Lightly work the wax over the finish until it's thoroughly covered. Allow the wax to dry, wipe it off, and buff the wood surface to a lustrous finish.
Repairing Shellac Finishes
Moisture and humidity can damage a wood surface with a shellac finish. It may become dull or a white residue will appear that's tough to remove. If the finish develops water spots, the repair is relatively simple. Use straight alcohol on a pad and remove the shellac. Then brush or pad on coats of leftover shellac, rubbing it out until the finish is once again even.
To fix scratches on a surface, use a fine artist's brush to fill in the scratch with leftover shellac. Buff the finish to even out the color between the repaired scratch and the surrounding finish.