Experienced woodworkers know that wood finishing is certainly one of the biggest tasks when it comes to their craft. While the precise and intricate machining required to complete their job doesn’t daunt them, and the complex joinery of the many different parts leaves them equally unafraid; you will find that even the most professional woodworkers may slightly cringe when it comes to applying a finish.
Many of them spend a lot of time thinking about what the best finish is for any particular project – which is precisely what we’re going to talk about here today!
Picking The Right Wood Finish
Obviously, regardless of the project in question – you need to make sure you’ve got the proper cherry on top of the cake. This holds true in woodworking and home projects alike.
For example, some people like picking even the tiniest details of their home aesthetic with extreme care; or adding more functionality through products like soundproof curtains. And when you’re doing some woodworking for your household, the proverbial cherry is the finish.
When it comes to finishing products, there are various categories you can group them into; based on the level of protection that they enable, as well as their general qualities.
Mostly, we’re talking about water-based finishes, lacquers, shellacs, varnishes, oils, and waxes – many of which we’ll talk about in more detail below.
While these methods and products all have different aesthetic appeal, repairability, application difficulty, and durability, there is no single greatest finish out there. Instead, you need to make a trade-off based on informed opinions and take the specifics of your project into account.
If we take a look at all of the different wood finishes out there, we can classify them all into two categories, based on the way they dry.
There are evaporative finishes – like water-based finishes, shellac, and lacquer – that leave a hard film once the solvents evaporate. Such finishes can always dissolve again if you apply the solvent for thinning them; meaning that they’re less durable than the other, reactive finishes.
Speaking of which, reactive finishes are varnishes, catalyzed lacquers, and stuff like linseed. These also have evaporating solvents, but they dry (or as the term is, “cure”) by either reacting with a chemical or with the outside air.
So, the finishes go through a chemical change while they cure; meaning that you can’t redissolve them in the thinning solvent. Obviously, such finishes will hold up to extensive chemical use and heat much better.
It’s safe to say that most woodworkers don’t think that wax is actually a finish on its own. Some people use beeswax, carnauba and other types of paste wax but only for polishing furniture pieces that already have their finish.
Tung oil and linseed oil, the most commonly used drying oils, are quite inexpensive compared to some of the other options we’re going to list here. And perhaps more importantly, they’re readily available.
There’s a reason why they’re referred to as “true oils” – to let them stand apart from some products that are marketed as oil finishes, but really aren’t, or semi-drying and nondrying oil like soybean.
There are a few forms of linseed oil available for purchasing. For example, there’s the raw, unrefined linseed oil. You won’t find this used on woodworking very often because it’s quite slow to dry.
However, people figured out long ago that boiling this oil makes for a thicker finishing product; thus, one that dries far quicker.
This is what we call polymerized, or heat-treated oil. These days, you’re most likely to find boiled linseed oil that’s not really boiled, but raw oil with a mixture of chemicals that achieves the same sped-up drying effect.
On the other hand, we’ve got tung oil – one that’s been derived from the nuts of Asian trees. To be more specific, these kinds of trees originated in Asia, but they’ve since been successfully cultivated all around the world.
Just like linseed oil, you can also find boiled and raw tung oil; with the same effect on the duration of the drying process. On top of expediting the time needed for the finish to dry, boiling reduces the likelihood of tung oil “frosting” – or drying enough to obtain a whitish appearance.
Compared to linseed oil, tung oil is generally paler, and it boasts a higher degree of resistance to moisture.
Both tung oil and linseed oil represent penetrating finishes – in other words, they harden after penetrating the very fibers of the wood beneath.
Also, in practice, they are definitely among the easiest kinds of finish you can apply. You only need to wipe these on the surface in question, wait for them to penetrate surface layers of the wood, and then wipe off anything that remains as excess.
Compared to lacquer or varnish, they won’t form any kind of surface film, seeing as their buildup is far softer.
Next up, we’ve got varnish. This is a finish produced out of durable and tough synthetic resins, additionally modified using drying oils. Usually, the labels on varnish cans will list out what kind of resin we’re talking about – like urethane, phenolic, or alkyd – as well as the oil in question (such as linseed or tung).
Just like with true oils, the process for curing that varnishes use is, in essence, polymerization. However, the resins that are found within will make these finishes far more long-lasting compared to pure oil.
In general, oil-based varnishes are the most common finish that the average woodworker will apply. In terms of resistance to external elements like solvents, heat, and water – the varnish will likely surpass a majority of other finishes.
The types of varnishes that have the highest percentage of oil can be referred to as long-oil varnishes. Among these are many of the interior varnishes available on the average retail market, as well as spar and marine varnishes. Compared to other types of varnish, the long-oil varieties are softer and more elastic.