Finishing Touch: Shellac – a no-full finish
Shellac is a wonderful finish that highlights wood figure and enhances colour as well as – many would say better – than any other topcoat. It’s a film finish, meaning it builds up a thin layer, or film, on top of the wood’s surface. It’s one of the most uncomplicated finishes to apply and probably the fastest drying. On top of that, it’s likely the easiest finish on the market to repair. Because it dries so quickly there’s much less chance of dust contaminating the finish.
When cured, a shellac finish offers decent wear resistance and excellent protection from moisture transfer. Another great feature of shellac is that you can apply just about any kind of film finish on top of a cured coat of shellac, including waterborne finishes like polyurethane.
Because there is virtually no odour after it cures, I like to use it inside drawers, cabinets and small boxes. You can also use it on items that aren’t handled on a daily basis, such as display cases, keepsake boxes, carvings, turnings, picture frames, trimwork and the like.
Furniture refinishers sometimes use shellac as a base coat for their work. Shellac will go a long way in sealing in a piece of furniture and creating a barrier between the newly stripped wood and the rest of the finish that will be applied on top of it. This helps seal in any pitch, wax, stains, odours and other contaminants that may be present that could negatively affect the new finish that will be applied. When painting wood, mainly in home improvement situations, a coat of shellac-based primer will eliminate the knot bleed-through that happens when you paint over a knot. This is especially helpful when painting pine, spruce and other knotty woods a lighter colour, as the pitch that bleeds through will otherwise become very obvious after a few weeks.
Garnet shellac flakes (left) are a lot darker than blonde shellac flakes (right). There are a few different tints between these two, as well as super blonde, which is almost colourless.
Different Tints, Different Looks
Here are two samples of walnut and white ash. The panel on the left of both of the samples is raw wood. The centre panel has been finished with blonde shellac. The panel on the left is garnet shellac. The darker garnet shellac causes the lighter white ash sample to look muddy.
Shellac Mixing Ratios
Mix, Then Let Sit
Mix the flakes and alcohol together in a glass container, then wait. The flakes dissolve relatively slowly. Mixing or shaking the jar from time to time can speed the process.
Six Hours Later
After six hours the flakes have almost fully dissolved in the alcohol. Another stir and a bit more time and the shellac is ready to use.
Make a Pad
Wad up a piece of cloth then wrap it with another piece, ensuring the outer surface of the pad is smooth. (Photo by Rob Brown)
Duguay prefers applying shellac with a lint-free cloth padded up into a ball. He recharges the pad regularly.
Shellac doesn’t stand up well to water, discolouring after a relatively short period of time. The white spots here appeared after about 30 minutes.
What is shellac?
The lac insect is found mainly in Thailand and India. They spend their lives in trees, ingesting sap, then secreting a tunnel-like structure that sticks to the bark of the tree as the lac insect moves around. Shellac is made by mixing the secretions from female lac insects with denatured alcohol or another appropriate solvent.
In addition to being a great finish for woodworkers and DIYers, shellac is also edible, and sometimes used to coat pills, candy and even fruits in the produce aisle. Next time you buy chocolate-covered almonds take a close look at their surface; the light layer of shellac reduces the likelihood the chocolate will smear in transit or melt on touch.
Shellac flakes are available in different tints, ranging from a light blonde to a rich amber colour. What tint you select for your next project depends on two considerations. The first regards the tone of the wood you’re finishing. While it’s somewhat common to use a light blonde shellac on a dark wood, lighter shellac is often used on lighter woods, like maple and ash. Darker shellac is often used on darker, richer woods such as walnut and mahogany. If a dark shellac is used on a light wood the result often looks muddy and unpleasant. The second consideration is personal preference. If you like the look of a specific shellac on a specific wood, then you should use it. As always, test out the finish on a sample before committing to an entire project.
Waxed vs. de-waxed
Shellac, both flakes and premixed versions, naturally has wax in it, but can be purchased in standard waxed or de-waxed versions. If the can, jar or bag doesn’t state whether it’s de-waxed or not, it very likely hasn’t been de-waxed. Often the wax won’t cause any problems, but there are other times when using de-waxed shellac is strongly encouraged. It all depends on how you’re using the shellac and what your expectations of the finish are.
The benefits of using a shellac that has wax in it is that it’s slightly easier to sand and it’s likely cheaper. I’ve heard some say wax will help a heavy application of shellac level off while it’s still wet, but I can’t speak to this. It also might have a slightly better sheen, though this is personal preference, and the sheen of the cured shellac finish can be adjusted by using steel wool and wax.
There are a few downsides to using a shellac with wax. The cured finish is slightly less water resistant and transparent, but likely the biggest downside is that coats of finish applied on top of a waxed shellac won’t adhere to the shellac well. This is more of a problem if you’re using shellac as a sealer while refinishing furniture.
It’s quick to make
To make your own shellac finish all you need are some shellac flakes (use dewaxed if you plan to use the shellac as a sealer under another finish), denatured alcohol (I use 99% isopropyl alcohol, available from most pharmacies) and a glass bottle. The ratio of shellac flakes to alcohol is called the “cut.” Slightly more or less of each component doesn’t matter. Technically speaking, a 1-pound cut includes 1 pound of shellac flakes in a gallon of denatured alcohol. I almost always use a 2-pound cut. Add the components to the bottle and wait overnight for the flakes to dissolve. You can speed things up by shaking the bottle or stirring the contents every few hours.
If the idea of working with ratios and exact quantities turns you off, don’t worry. Many people add some shellac flakes to a glass jar, pour in some alcohol, mix and wait until the shellac flakes are dissolved. With a bit of practice, you’ll be able to quickly figure out a mixture that’s close enough to what you want.
Depending on the grade you purchase, it may be worth your time to strain the shellac after the flakes have dissolved. This helps remove any impurities from the manufacturing process.
Easy to use
Shellac can be sprayed, brushed or wiped on. Most of the time I apply it with a cloth, somewhat similar to the pad used in French polishing. For very large surfaces, such as the inside of a large cabinet, I’ll use a brush. To wipe it on, ball up a piece of lint-free cotton or linen cloth and pour some shellac onto the cloth or dip the cloth into the shellac. Apply the shellac in a sweeping motion across the wood surface using light pressure. A small brush comes in handy for getting the shellac into tight areas and corners.
Shellac dries very quickly so you’ll need to constantly recharge the cloth. You can apply a few quick coats then let them dry. You’ll quickly get the feel for how fast you can apply a few coats. Often waiting 10 or 15 seconds is enough to apply another coat, but this depends on how strong of a cut you’re using. A 1-pound cut will dry faster than a 3-pound cut because there’s more shellac and less alcohol in a 3-pound cut. Having said that, you should only apply a few coats at a time, then put the project aside and let it dry thoroughly.
Don’t worry if you miss spots. Wait an hour or so and lay on another coat or two. Each coat will dissolve into the previous one and there’s no need to sand between coats.
You can lay down as many coats as you want. For a 2-pound cut I lay on five to six coats. Generally speaking, stop once the look and feel of the finish is to your liking. To repair a shellac finish use steel wool or a synthetic abrasive pad and alcohol to remove the damaged finish and reapply as described above.
Keep it glossy or reduce the sheen
Regardless of the colour of flakes you use, all shellac finishes produce a gloss sheen. If you prefer a satin sheen just rub the finish lightly with #0000 steel wool. Do so after the finish has fully cured – at least a week after your last coat. Two or three weeks is even better. If you notice any flat spots on the surface, apply another coat or two of shellac again, wait for the finish to cure and rebuff. I like to topcoat with a paste wax, which gives a wonderfully silky-smooth feel to the finish.
Like any finish, shellac has its drawbacks. Because it dries very quickly there can be no dallying around when applying it, especially if you’re brushing it on, as it tends to ridge at the edge of brush strokes.
It’s not as durable as modern film finishes, nor is it heat- or water-resistant. Water left standing on a shellac surface will leave white spots while alkalis like lye and ammonia, and of course alcohol, will damage the finish. Don’t use shellac on coffee tables, kitchen tables, countertops or islands, or anything in the bathroom.
If you’re finishing a project with a lot of flat surfaces and few inner corners or joints, shellac can easily be applied. If there are a lot of inner adjoining surfaces, like the inside of a box or the kumiko gridwork of a shoji screen, wiping or brushing on shellac might cause challenges. It’s easier to spray projects like this. It truly depends on your level of skill when it comes to applying a coat of finish.
When stored properly, shellac flakes should last about three years. However, after the flakes have been dissolved in alcohol the finish has only an eight- or nine-month shelf life. Oxygen, heat and moisture all play a role in degrading the finish, making it less likely to harden and lowering its resistance to water. It’s good practice to make only enough finish to use on the project at hand.
Pre-mixed shellac is a bit trickier, as you don’t necessarily know when the mixture was made. One way to test out a premixed shellac before applying it to a project is to put a few drops on a piece of wood and let it dry overnight. If it hardens properly it’s likely safe to use. A common-sense approach is needed, though. If you bought the premixed shellac 10 years ago, I wouldn’t risk using it, even if a few drops of it does harden overnight.
Where to get flakes
Wood Essence (WoodEssence.com) has the widest selection of high-quality, wax-free shellac flakes, but companies like Lee Valley and many others carry shellac in both flake and premixed versions. There are seven shades to choose from, including ultra-blonde or super-blonde, the clearest and lightest shellac, good for use on light-toned woods. Dark garnet is excellent for highlighting dark-coloured woods like mahogany, sapele and walnut.
You can create custom colours by adding aniline dyes or universal tinting colours (UTCs) to shellac. The flakes are available in 1/4-to-3-pound sizes. WoodEssence.com/Shellac/Dry-Shellac
You’ve likely heard the term “French polishing” in relation to shellac. While shellac is a finishing product, French polishing is a technique you use to obtain a very high gloss finish that has exceptional colour and luster. It’s a lengthy, repetitive process in which you use a cloth pad dampened with shellac and a small amount of oil to apply the shellac. If you’d like to give it a try read the article online called “French Polishing.”
Watch a video
Rob Brown, editor of Canadian Woodworking & Home Improvement magazine, shows how easy it is to create a beautiful shellac finish on wood.