Reaching the point in a woodworking project where a decision needs to be made means we’ve chosen our wood, cut the wood into the right pieces and shapes, and assembled our project.
Each of those choices was made with some care – the project and the wood.
Each of those steps to cut and assemble was carefully planned and executed.
The remaining steps are to choose and then apply a finish. We want our project to have a nice finish, look good, remain durable, and offer the right degree of protection to the wood. The degree of protection will have much to do with the use to which the project will be put when completed.
In the case of something that will not get a lot of wear and tear and will not be abused, it might be something like window or door trim or maybe shelving. Used and abused might include flooring or a dining room table. It might be something as simple as wooden coasters for our coffee or tea mug or our cold drink in a frosty glass or mug.
Thus, the type of finish needs to match well with the use. In the case of a wooden coaster, our concerns would be the ability to withstand heat (coffee or tea mug) and moisture, either from a sweating glass or merely liquid spills.
So, the type of finish we choose must be durable enough to withstand any of those possibilities.
Choice of Durable Finishes for Wooden Coasters
When it comes to wood finishes, and for our purposes today, we will exclude stains from the discussion; we have two very basic categories: those that will penetrate the wood fibers and those that will simply provide a film finish.
In the former category, we’re talking about finishing oils, and in the latter, we are talking about finishes (both oil-based and water-based) that will coat the wood with a protective film.
Oil Finishes For Wood Coasters
In this category, we have three to consider: linseed oil, tung oil, and Danish oil. We’ve used each of these, but admittedly not on wooden coasters. However, their use on wood is consistent no matter the project on which they are used.
We know it comes from the flax plant, its seeds, and stalks. While it is used for its nutritional value in a raw state, we know it as a preservative for wood and rope. Written evidence of its use dates back to the 6th century CE, and it has been produced in the US since 1793.
It will fully penetrate wood and provide strong protection against the elements. It should be used only on bare wood or wood that has already been oiled. It’s easy to apply with either a brush or a cloth and will bring out the natural color and grain of the wood.
However, it takes a long time to dry, and this is the biggest knock on the use of raw linseed oil. To speed up the drying time, “boiled” linseed oil was developed. Raw linseed oil is mixed with oil that has had hot air forced through it, and then further processed by adding metallic thinners that enhance drying time, reducing it from 1-2 months down to 1-3 days, depending on the surrounding environment.
This boiled linseed oil will penetrate deeply into the wood fibers and provide protection to them. That protection, though, does not extend to water, as boiled linseed oil does not add a waterproof quality. Since wooden coasters are susceptible to spills and sweating glasses, we can cross linseed oil off the list for us today as a standalone finish.
The use of tung oil dates back at least 2500 years in China, which is where the tung tree grows as a native plant. It was used to waterproof ships, and we noted in a previous piece of tung oil being used on oil-paper umbrellas because of its waterproofing quality.
It’s a food-safe product and can be used on kitchen-type items as a result. Wooden coasters would fall in that category, we suppose.
Tung oil penetrates deeply, and at least 3 coats are advised for that penetration depth. When exposed to air, it will harden, a process referred to as polymerization. That process will offer great water resistance, and thus its use on ships historically, as well as on wooden boat decks today.
As a result, we can keep tung oil in consideration for a durable finish for wooden coasters.
Linseed oil is from flax seed and was once commonly called flaxseed oil; tung oil is from the seed of the tung tree, but Danish oil does not come from Danes (yes, we know – a bad joke). Actually, there is no generally accepted formula for the blend that is called Danish Oil.
It is often made of tung oil, rosewood oil, or polymerized linseed oil. Again, there’s no definitive formula, and its constitution varies from manufacturer to manufacturer.
It dries to a hard finish that builds up with each subsequent coat. It is resistant to liquids but not waterproof. When thoroughly dried, though, it is resistant to chipping and cracking. It dries to a satin or semi-gloss finish and will tend to darken wood when used.
We’re not as apt to recommend its use on wooden coasters, though, because it is not waterproof. Resistant to liquid spills, yes, but not fully waterproof. So, we’ll cross its use off the list in this instance.
Moving on from oil finishes, we will now consider a couple of other finishes that will provide a durable film finish to protect wooden coasters.
Polyurethane Finish For Wood Coasters
We’re all familiar with polyurethane, and most of us have used or continue to use it as a finish material for our projects.
Oil-based polyurethane is one type of it, using oil as the medium in which the polymers and urethane are suspended. It smells, is toxic, and needs protective gear like a respirator when being used, as well as a well-ventilated room with lots of good air circulation. It also takes a very long time to dry and cure.
But, it will provide a film finish with a plastic look and feel to it that is waterproof, hard, and durable. Many wood floor installers will tend to choose oil-based poly to finish off their work. That waterproof finish from an oil-based finish is of interest to us when it comes to protecting a wooden coaster, so we’ll keep it on the list.
Water-based polyurethane is the other type of product, using (as you might expect) water as the medium to support the polymers and urethane. It doesn’t have anywhere near the noxious odor of its oil-based cousin, is not as toxic (although we would not drink it), dries and hardens much faster than oil-based, and offers a durable and hard film finish that is waterproof.
Its application is much less dramatic in that no safety gear is absolutely necessary, although good air circulation will speed up the drying process so that you can get a second coat applied on the same day as the first coat. Speaking of coats, the water-based poly will require more coats, anywhere from 4-6, to be most effective.
Again, it dries to a hard and durable finish, a film of plastic protecting the wood, and so it stays on the list for wooden coasters.
Lacquer Finish For Wood Coasters
Lacquer is another common and popular type of finish often found on high-end furniture. It’s fast-drying, dries to a clear and transparent finish, and is impervious to water. It does not yellow with age and requires little to no maintenance. You can even buy it in a spray can for easy application.
There are a number of lacquer types, and although we will not go into great detail, we will mention them:
Nitrocellulose, originally used as a car finish in the 1950s, and now often used to finish high-end musical instruments. It dries to a high gloss finish and gives a rich luster and patina to some woods.
Acrylic, also developed in the 1950s, is used on lighter-colored woods like maple and ash. It dries to a water-white color and does not color with age.
Water-based, fewer hazardous chemicals, less toxic, odor-free, and more durable than the other types of lacquer. It lasts longer than acrylic lacquers and is cheaper. It’s very environmentally friendly and repairs easily when damaged. Resistant to chipping and waterproof, it remains on our list for wooden coasters.
Varnish For Wood Coasters
The last type of finish on our list is varnish. It is made from resins, oils, and solvents and is highly resistant to scratches and abrasions on wood. It usually has a yellowish tint to it because of the way in which it is made.
It waterproofs wood, too, in addition to protecting it from scratches. It’s a hard film coating on the wood, very durable, and is well-suited for outdoor uses as well as indoor. The solvents evaporate during the drying process, leaving behind the constituents that oxidize and polymerize to form that durable film coating.
Waterproof and durable obviously mean we leave it on the list of finishes for coasters.
No Wooden Coaster Videos Today
While we usually include some videos about the topic of our articles, today, we offer none. We all know about finishing our projects, and we can now see the wide variety of options for the type of finish we want for wooden coasters. We also know how to apply them, whether by brush (bristle or foam), cloth, or spray can.
It’s the durable, hard, and waterproof finish we want to use for them, knowing that there will be spills and sweat. Additionally, we also know we’ll be washing the coasters. We have varnish, lacquer, poly, and tung oil on our list of recommendations for you.
Stain may or may not be involved; your choice, with one of these topcoats, and coating tung oil with a poly or varnish topcoat would also work.
The final word we will offer is that coasters can end up being good uses for scrap wood after a larger project. Don’t throw those scraps away or toss them in the fireplace – make coasters out of them.