There is a world of difference between the various types of finish one might use on their woodworking projects. There are four categories of finishes: polyurethane, varnish, Shellac, and lacquer. What is the difference?
Well, let’s break it down below!
What is Polyurethane
This versatile finish can be sprayed or brushed on virtually any wood surface with impressive results. It’s highly effective at resisting moisture penetration, it is very durable and easy to use.
They’re water-based and they can be used indoors or outdoors. Polyurethanes also provide some abrasion resistance and/or a protective topcoat that helps preserve the wood underneath.
What is Varnish
Vanish is neither a lacquer nor a shellac. However, it is related to polyurethane in the sense that Poly is a kind of Polyurethane. Poly, on the other hand, is tougher, stiffer, and contains less oil. Generic Varnish is oily and more flexible.
While you can use varnishes on outdoor pieces, do not use them as primary finishes in high-traffic areas unless you have sealed your piece with something like spar urethane first.
What is Shellac?
Shellac is a natural finish made from cocoons of the lac bug, which is harvested by scraping the bark off certain trees in India and Thailand. The active ingredient that makes shellac so special for woodworking is its resin content.
Shellac resin can penetrate all wood pores to fill up voids and help seal an exposed surface of the wood. Shellac is often used on furniture because it gives a soft satin finish that brightens the wood’s natural color. It also fills in any open pores to help repel stains and liquids.
What is Lacquer
Lacquer is also a finish, but one that is much harder to apply than either shellac or polyurethane. A single can of lacquer will go a very long way. You only need to use it on projects where extreme durability is required like table tops that are subject to wet dinner plates.
It’s usually used as a sealing coat on furniture assembled with wood glue. It dries to an incredibly hard finish that is flexible enough to not break from bending but strong enough to hold up well under extreme stress.