Shellac vs Polyurethane: Which Should You Use? (2023 Guide)
Two common wood finishes are shellac and polyurethane. These finishes are pretty similar, but there are also some key differences that you need to know.
Below, I break down shellac vs polyurethane so you can know when you should use each and which is better overall. Let’s dig in!
Shellac is non-toxic, easy to apply, thin, and great at highlighting wood’s grain and color. However, it isn’t the most durable finish, yet it still provides decent protection. Polyurethane is much more durable, but it’s more toxic and somewhat harder to apply. Plus, polyurethane can take multiple weeks to cure, whereas shellac dries in days.
In This Article:
What is Shellac?
Shellac is a kind of resin that’s secreted by the female lac bug. These bugs can be found on certain trees throughout India and Thailand, and the resin they secrete consists of jalaric acid, aleuritic acid, shellolic acid, and other natural waxes.
The liquid shellac that woodworkers use is the result of dissolving dried shellac flakes in alcohol.
Before the invention of nitrocellulose lacquer—a commonly used brushing lacquer—Shellac was one of the dominant wood finishes in the western world. In fact, phonographs and the 78 rpm gramophone records that were played on them were made out of shellac.
In addition to being a natural primer and sealant, shellac is also a tannin- and odor-blocker. It can also be used as a stain or high-gloss finish.
Checkout this epoxy vs polyurethane guide to find out which you should use!
Easy to Apply and Remove
Shellac is an easy-to-apply wood finish, in large part because you don’t need many coats to achieve an attractive and sound finish; usually two to three coats are enough.
And since it’s brushed on, it’s easy to disperse and it’s easy to apply it in tough-to-reach spaces, like joints, crevices, and gaps.
Easy to Repair
Shellac is easy to repair as well. When you apply shellac finish to a pre-existing coat, it won’t take long for the two coats to blend.
Plus, since this finish is pretty thin, you won’t have to apply a lot to touch up the surface. Just use enough to cover up the minor scratches and faded areas.
Visually Appealing When Applied to the Right Wood Surfaces
It’s best to use shellac with lighter woods. The reason why is because shellac can accentuate the colors most softwoods boast, and the same can’t be said for other wood finishes.
Anything medium-brown or lighter should be coated with shellac. For darker wood, apply lacquer or polyurethane.
Another quality that makes shellac attractive is it’s not a synthetic resin. So when you use it, you don’t have to worry about it being toxic.
Even though it doesn’t contain engineered chemicals and other components, it can still ensure protection while accentuating the grain pattern and the color of the wood it’s applied to.
Since it doesn’t emit harmful fumes, you don’t have to leave your home after it’s been applied like you would polyurethane.
Decent Water Resistance
Even multiple coats of shellac won’t make a wood surface totally waterproof, but these will make it quite water resistant. This is in part why shellac is used as a sealer.
So if you apply shellac to your kitchen cabinets, you won’t have to worry about them being negatively affected when water gets splashed on them.
That said, shellac isn’t a good finish for surfaces that are constantly exposed to water like outdoor projects.
Although it isn’t the most durable finish, shellac does have decent UV resistance, so it can be used outdoors (as long as it’s shielded from the rain).
A lot of fine furniture that’s designed for outdoor use is finished with shellac—instead of polyurethane—because the visual appeal is more important than durability. Still, there’s enough durability to prevent the sun from wreaking havoc on the finish.
Oil-based poly, on the other hand, could turn a pale yellow if constantly exposed to the sun.
Not as Durable
An unfortunate and unavoidable downside of shellac is that it’s not as strong as other finishes. Even if you applied it in thick layers, it’s not going to provide the durable, long-lasting finish that other wood finishes provide.
For this reason, shellac is not applied to floors, stairs, tabletops, countertops, and other surfaces that are at a greater risk of being dented, dinged, scratched, or gouged.
Poor Heat Resistance
Shellac doesn’t resist heat well, and because of this you should think twice before applying it to kitchen furnishings. Prolonged exposure to high heat will wear down the finish and make the surface underneath more susceptible to damage.
What is Polyurethane?
Polyurethane, otherwise known as liquid plastic, is a commonly used varnish.
Once completely cured, polyurethane provides a durable finish. Even a thin coat can provide meaningful protection. Still, most woodworkers usually apply multiple coats of polyurethane.
Sometimes, polyurethane is thinned with mineral spirits so it’s easy to spread out, but this is really only necessary with oil-based poly.
Speaking of which, it’s important to point out the differences between oil-based polyurethane and water-based polyurethane.
Oil-Based Poly vs Water-Based Poly
Oil based polyurethane is thicker, more toxic, more durable, and it takes longer to cure (usually 30 days).
Water-based poly is thinner, contains less volatile organic compounds (VOC), isn’t as durable, dries much more quickly, and is colorless.
Because of its durability, oily polys are often used outdoors, whereas water polys are mainly used indoors.
Like other oil finishes, oil-based polyurethanes provide more durability, and this is a key reason why they’re applied to wood, wood-based products, and other surfaces.
The durability is mainly a result of composition. Also, since oily polys cure mainly above the wood’s surface, they’re stronger. Wood stain, on the other hand, is absorbed into the wood via its pores.
Since it’s a durable finish, it should come as no surprise that both oil-based and water-based polyurethanes are long-lasting. However, polyurethane finish needs to be applied properly and maintained well to last several years.
Easy to Apply
Applying water-based polyurethane and oil-based versions is easy, provided you have all the materials you need, an ideal space for applying poly, and the time it takes for the polyurethane to cure. By using a polyurethane brush you can easily apply the substance to your projects in minutes.
After you apply the first coat, all you have to do is rough it up a bit with steel wool or sandpaper. Then you can apply the next coat.
In truth, it’s a simple and easy process as long as you have patience.
Variety of Options
Because there are different polyurethane types, you can use this with light woods and darker woods. Specifically, the water-based versions go with the lighter materials because they’re colorless, whereas the yellowish, amber-tinted oil-based polyurethanes work best with dark wood.
Emits Toxic Fumes While Curing
Both oil-based and water-based polys emit fumes as they’re curing. For this reason, you have to be out of your home after applying polyurethane on a large scale, such as well it’s applied to hardwood floors.
In liquid form is when it emits the most fumes, and overexposure to these could make you pass out.
Can Discolor Surfaces
Oil-based polyurethane in particular—because it displays a warm glow after curing—can discolor wood surfaces. Again, this is why oily polys aren’t used with soft woods, as these tend to be light in color.
Differences Between Shellac and Polyurethane
Shellac vs Polyurethane: Appearance
When it comes to appearance, shellac is much more visually appealing than both kinds of polyurethane. Shellac can bring out the unique features a piece of wood possesses, and because it’s so thin you can barely tell it’s there sometimes.
With polyurethane, you could get the plastic-like appearance, especially if you don’t apply it right.
One thing to keep in mind about shellac, however, is that it doesn’t withstand heat all that well. So if you put a hot mug on an end table that’s coated with shellac, you may find that the mug left a heat mark that’s tough to remove.
Shellac vs Polyurethane: Durability
But in the durability department, polyurethane is superior to shellac. Even polyurethane that’s been thinned by paint thinner or denatured alcohol can provide a protective finish.
Shellac mixed with a hardener is more durable than shellac alone, but you may not like the look of mixed shellac.
It doesn’t take many layers of polyurethane to form a protective barrier, so refrain from applying too many layers.
Shellac vs Polyurethane: Water Resistance
Both finishes resist water well, but oil-based polyurethane that’s applied properly can ensure a near-waterproof seal. This is the main reason why most outdoor wood furnishings are coated with an oil poly.
Shellac can resist moisture that’s in the air and it won’t be damaged by a splash here and there. But frequent exposure to a large volume of water can wear this finish down quite quickly.
For this reason, if you’re going to use shellac in your kitchen, it’s best to keep furnishings that are coated with it away from your sink and dishwasher.
Shellac vs Polyurethane: Drying Color
Both shellac and oil poly have some color to them; water-based polyurethanes do not.
It’s important to consider the yellowish/amber tone that shellac and oil poly have, especially if you’re going to be applying either to surfaces that are on the lighter side.
These finishes can distort the natural colors of the surfaces they’re applied to, causing a blotchy or discolored mess that isn’t visually appealing in the slightest.
Shellac vs Polyurethane: Drying Time
Drying time is an important thing to consider when applying shellac or polyurethane.
In the case of shellac, you don’t have to wait very long for a coat to dry. Usually, a thin coat dries in 30 minutes to an hour.
So even if you’re applying four to five coats, you can still get the job done in one day.
Both kinds of polyurethane take much longer to cure. In the case of water poly, you’re looking at a two-week cure time; that’s doubled for oily poly.
These finishes also take longer to apply. In the case of water poly, you have to wait 45 minutes to an hour before applying another coat. With oily polys, you need to allow for five to seven hours of drying time.
You can check out my polyurethane drying guide for more info on how long it takes to dry!
Shellac vs Polyurethane: Ease of Application
Both finishes are equally easy to apply.
With shellac, it’s best to use a natural-bristle brush. Polyurethane, on the other hand, should be rolled out with a roller. Water-based polyurethane, however, can be sprayed on because it’s so thin.
You could also apply polyurethane with a foam brush or a dry cloth. I personally like applying water poly with a cotton rag because this way I avoid applying too much poly.
Polyurethane also comes in spray cans, but I’m not a big fan, as it’s hard to get an even finish with them. That said, some woodworkers are masters with poly spray cans.
When to Use Shellac
Working With Softwoods
Shellac is mainly used for finishing high-end furniture and antiques.
And because it highlights wood’s features without diminishing its natural qualities, you can find all kinds of shellac-coated furnishings nowadays, including picture frames, clocks, and shelves.
So if your wood has a light-brown color and a unique grain, shellac will bring both elements to the forefront and provide protection all the while.
But because of the purposes shellac is used for, it comes with a higher price than most polyurethanes.
Also, it has a very short shelf life. This point is definitely something you should keep in mind if you don’t want to waste money.
When Durability Isn’t a Chief Concern
If durability isn’t important, then consider using shellac. Furniture that’s used indoors is often coated with shellac because this kind of furniture isn’t subjected to things that can damage it routinely.
Outdoor furniture, on the other hand, is subjected to the elements, unpredictable temperature fluctuations, and a range of other things that can wear it down.
When You Want a More Eco-Friendly Finish
If you’re looking for a more eco-friendly option, go with shellac over polyurethane. Shellac is made of natural components and isn’t toxic. The same can’t be said for polyurethane.
Also, applying shellac doesn’t force you to leave your home for five to seven days. Again, the same can’t be said for polyurethane.
And even though shellac is made of natural components, it’s still durable enough to provide decent protection.
When to Use Polyurethane
When Durability Is Important
Polyurethane is chosen over shellac when durability is of upmost importance. After all, the more durable a surface is, the longer it’ll last.
Polyurethane is not only heat- and water-resistant but also UV- and corrosion-resistant.
And if you mix polyurethane well and apply it correctly, you can get the unmatched durability without compromising the surface’s natural visual appeal.
Even though water poly is less durable than oil poly, it still holds up much better than shellac—and it’s way more affordable!
In the end, it’s hard to say that one finish is superior to the other. In truth, both can be used to great effect in different circumstances.
Shellac is ideal if you want to accentuate wood’s grain and color while ensuring added protection. Polyurethane is a good option if durability is what you want most out of the finish.