One of the many decisions involved in any woodworking project is deciding the finish to apply. Beginning woodworkers think they only have two basic choices: paint or varnish. But as the woodworker gains experience, they also experiment with other forms of finish, seeking out what will make their project look the best. This is especially true with fine woodworking projects using exotic hardwoods.
Any finish should be able to do two things: enhance the beauty of the woodworking project and protect the wood from damage, specifically water-related damage. While the amount of protection that a particular project needs may change, due to where it is located and the wood that the project is made of, weather isn’t the only thing those projects need protection from. Fungi, wood-eating insects and grimy hands are all capable of damaging the beauty of a superbly executed woodworking project.
But the bigger concern in most woodworkers’ minds is how the finish will enhance the beauty of the project. Many finishes will enhance the natural color of the wood, bringing out the grain, making it more obvious. Even wood types with dramatic grains or grain coloration can benefit from the judicious application of the right sort of finish. The fact that those finishes also protect the wood at the same time is an added benefit to most woodworkers.
However, the real concern should be how that finish is going to protect the completed project. Properly applied, all finishes will make a project look good. Varnishes can provide a much glossier finish, while oils will provide a warmer, softer look. But varnish provides more protection to the project from impact and abrasion. The tradeoff there is that it takes a whole lot more work to repair damage to a varnished finish, than it does to an oiled finish. In many cases, if the need for repair is caught soon enough, all that’s required to repair the oil finish is the application of another coat of oil. Oil/varnish mixes, like birchwood Casey’s “Tru-Oil” mix the benefits of both.
Tru-oil is a linseed-based oil product, with other oils, mineral spirits and urethane varnish mixed in. The non-drying elements have been removed to the mix, ensuring that the finish will dry completely. It provides a very durable finish, which is still relatively easy to repair if damaged. Some woodworkers, gun makers and luthiers swear by Tru-Oil as being the best wood finish available.
As a combined oil and varnish mix, Tru-Oil provides the best of both worlds, soaking into the wood to enhance the grain and protect it from excessive drying, while depositing a thin coat of varnish on the surface, providing abrasion resistance. When repairs are necessary, it is easier to sand off the thin varnish coat and reapply Tru-Oil to the wood than it is to sand off an actual varnish finish, going back to bare wood and refinishing it.
This finish is different than Tung oil in that Tung oil soaks into the wood more, not leaving a hard finish on the surface. It is more like Danish oil, which is another oil-varnish mix; but Tru-Oil builds up more of a surface finish than Danish oil does.
Tru-Oil is predominantly used for finishing gunstocks, although it has gained a considerably following in the musical instrument industry, especially amongst high-end string instrument builders. The combination of finish quality and abrasion protection for the wood works out just as well for instruments, as it does for firearms. Abrasion can be a big issue on string instruments, especially on the back of the neck and the area that a guitar pick would cross over, if the pick guard is inadequate.
Another place where oil and oil/varnish finishes is popular is in finishing projects which will be used for preparing and serving food. Varnish should not be used in any application where the surface is likely to be cut by a knife, such as cutting boards. This applies to Tru-Oil and other oil/varnish mixes as well. But it can be used well for wood serving plates, platters and bowls. The combination of oil and varnish will protect these dishes from being damaged by moist and food. At the same time, these finishes are food-safe; it is even safe to ingest polyurethane, although it is not recommended.
It is easy to apply Tru-Oil to a project, as it is a wiping finish. That saves having to use paintbrushes and then having to clean the brush. However, a small brush might still be useful in a situation where there is fine carving or molding work, where the finish won’t get down into the details without brushing.
The biggest mistake that new users of Tru-Oil make is in not applying enough coatings of the finish. As with any other wood finish, the more coats applied, the better the project ends up looking. To get the most out of Tru-Oil, a minimum of 8 coats should be applied, allowing the finish time to dry between coats and sanding lightly with 600 grit sandpaper. This is not to say that only 8 coats can be applied, as some users start with a minimum of 12 coats. Applying thicker coats isn’t better and may result in drips and sags on the surface. The final coat should be allowed a week to dry fully.
Tru-oil can be used in conjunction with other finishes. As with any wood finish, the wood can be stained before applying the Tru-oil. Just allow the wood adequate time to dry, so that the finish can soak in. Once sufficient coats of Tru-oil have been applied to the project, it can be waxed or varnished over, if desired. However, while varnishing will provide for a tougher, more durable finish, the finish will be harder to repair, should that become necessary. Wax is easy to repair, and can be applied either alone or over varnish, but it doesn’t work out well to try applying varnish over wax.