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Shellac is a non-toxic, quick-drying liquid. Woodworkers have been using it since the 19th century to solve a variety of woodworking problems. There are two methods for applying shellac to wood.
This article will teach you which method to choose for your project and give you step-by-step instructions for applying shellac.
What Is Shellac?
Shellac is made from a resinous secretion of the lac beetle. These colorful insects colonize tree branches, suck the sap out from inside, and secrete ‘sticklac’. The result is a cocoon-like tunnel.
The entire branch is harvested, processed, and purified, producing resin discs or shards. When these discs or shards of resin are combined with denatured alcohol, shellac is the result.
While lacquer and polyurethane wood finishes have become more common in the past century, DIYers and professional wood workers alike are returning to shellac as a versatile, non-toxic finish. It can be applied to wood as a primer, sealant, stain, or varnish. It’s tough enough to keep odors locked inside wood, but gentle enough for use as a food glaze.
How to Apply Shellac
Choosing an Application Method
The application method you choose for your project depends on the shape of your workpiece. Applying shellac with a pad is referred to as ‘French polishing, and tends to provide more even coverage with fewer drips and streaks. A brush does a better job of getting into corners or carvings.
It’s easier and more common just to buy a brush and get shellacking, and this is the best option for most projects. If you’re working on something special or want to try out an advanced technique, give French polishing a try.
Preparing to Apply Shellac
- Check the temperature and humidity. The dry time and performance of the shellac is related to the temperature and humidity of the surrounding air. The optimal conditions for applying a finish such as shellac would be air temperature of about 70 degrees, with humidity between 50 and 70 percent.
- Prepare your workspace. Place your workpiece on a drop cloth to catch any drips. Position the workpiece at a comfortable height for brushing on shellac. Ideally, you should be able to reach all edges of the workpiece without repositioning it.
- Sand your workpiece. Use sandpaper to smooth the surface of the wood. Start with coarse sandpaper, progressing to finer grits. Remove the sawdust with a vacuum or tack cloth.
- Raise and sand rogue surface fibers. Wiping a damp cotton cloth across your workpiece will raise any remaining loose wood fibers. Let the piece dry before sanding one more time with 400-grit sandpaper. Remove the bulk of the sawdust with a cloth, and then wipe the surface with denatured alcohol to finish the task.
- Mix your shellac. If you’re using store-bought shellac, it is likely that you want to thin it out somewhat by using denatured alcohol. If you’re making your own shellac, check the section below for more details.
- Pour the shellac into a clean container. As you brush on the shellac, the bristles may pick up dust or debris and introduce it to the container. Using a clean container for each job prevents contamination of the entire mixture.
- Test the mixture on a piece of scrap. Shellac dries quickly — within about 30 seconds. This means there is no time to smooth out drips. It’s best to try your technique on scrap before moving on to your workpiece. This also gives you a chance to test the spreadability of your shellac mixture.
Applying Shellac With a Brush
- Load the brush with shellac. Shellac should never be applied with a foam brush, as denatured alcohol dissolves foam. Instead, choose a natural bristle brush with fine bristles. A hake or china-bristle brush will work well. Dip about one inch of the bristles into the shellac mixture, and remove any excess to avoid drips.
- Brush on the shellac. Working in the direction of the grain, apply shellac in long, even, smooth strokes. The brush should glide along the surface of the wood. Reload the brush the moment you notice it dragging instead of gliding.
- Quickly apply the first layer. Aim for even coverage, but if you miss a spot, just keep moving. Shellac is a kind of varnish that builds over time, with each layer dissolving into the one before it, so you’ll have opportunities to fix your mistakes in subsequent layers.
Applying Shellac With A Pad
- Construct a polishing pad. Use gauze or wool to form a wad. This will be the core of your polishing pad, and serves as a reservoir of shellac. Wrap the wad in a cotton cloth.
- Load the pad with shellac. Using a squeeze bottle, add shellac to the core. Tap the polishing pad against a hard surface a few times to distribute the shellac.
- Seal the wood. Apply three thin, light coats of shellac to the entire surface, waiting a few minutes between each coat. Use a light wiping motion. Wipe in the same direction of the grain. Think of the pad as an airplane and the wood as a runway. You want to land the pad smoothly, keep it moving, and then lift it off again.
- Check your polishing pad. Do not press the pad into the wood, as this will release too much shellac. If the pad drags, a few drops of pure olive oil on the surface of the cotton will work well as a lubricant. If the cotton snags, tears, or picks up sawdust, replace it with a fresh piece of cotton.
- Wait for the base coat to dry. Place your pad in an airtight container to prevent it from drying out. The base coat of shellac should take about one hour to dry completely.
- Remove the oil, if necessary. If you use oil to lubricate your polishing pad, it will rise to the top of the shellac. The oil must be removed before another layer of shellac can be added. Wipe the dried surface lightly with alcohol to remove the oil.
- Fill in pores with pumice. Add 10 drops of alcohol to your mostly-depleted polishing pad core, and press it against a hard surface or the back of your hand to distribute the liquid. Shake pumice onto the surface of the polishing pad. Use random, circular motions to work a small amount of pumice into a small area of wood at a time. When the pores are filled and the finish feels smooth to the touch, you’re done.
- Apply the first layer of varnish. Put a new, clean cotton cover on your polishing pad. Add shellac to the core. Apply several coats at a time, allowing a few minutes for dry time between each coat. Use a circular motion and medium pressure to apply the shellac. Reload the pad with shellac as necessary.
- Allow one hour of dry time between layers. Store your pad in the airtight container again, and give your workpiece a few hours to dry completely before adding additional layers. The shellac will be dry to the touch after about 30 minutes, but needs a full hour to completely cure. Waiting can be the most difficult part of this project, but try to be patient.
- Apply additional layers. Using the same technique, build the varnish layer by layer to your desired thickness. Unlike with polyurethane or lacquer, no sanding is necessary between layers. Three to four layers is usually the least you can get away with. For thick, high-gloss shellac, as many as ten coats may be necessary.
- Dull the finish, if desired. Shellac is highly reflective. If you want a more matte look, use 0000 steel wool to buff out the top coat. Work a non-silicone paste wax into the wood.
How To Mix Shellac
As discussed in the intro, shellac is created when discs or shards of lac resin are combined with denatured alcohol. As the ratio of lac resin to denatured alcohol changes, so will the thickness of the shellac.
Shellac without enough denatured alcohol will be thick, gloppy and difficult to apply. If too much denatured alcohol is added, the shellac will become very thin, and may require additional coats. Striking the perfect balance depends on achieving the right ratio of resin to alcohol.
This ratio is known as the ‘cut’. A ‘two-pound cut’ of shellac is achieved by mixing two pounds of resin with one gallon of denatured alcohol. The resin is measured by weight, and the alcohol is measured by volume.
Most store-bought shellacs are a three or four-pound cut. This allows you to add as much denatured alcohol as you need, to achieve the mixture you desire. A two-pound cut is probably the most common ratio, with one-pound cuts being used to slowly build the varnish.
Watery looking half-pound coats are occasionally used as a wash cut.
When you know what ratio you want, simply add the flakes to the denatured alcohol and seal them in a closed container. The mixture is ready to use when the flakes are dissolved, which can take up to 24 hours. If you’re hoping for quicker results, shake them periodically.
Shellac is a resinous varnish that brings out the beauty and natural grain of wood while also offering protective qualities. It can be purchased pre-mixed, or mixed in the shop using raw materials. Use a pad to apply shellac to larger, flat areas.
A brush can be used to evenly apply shellac in hard-to-reach areas. Allow an hour of dry time between each layer of shellac. The resulting finish will be a mirror-like gloss. Steel wool and paste can be used to achieve a less shiny surface, if desired.