How to Choose the Right Woodstain or Finish for Carpentry DIY Projects
Woodstain, Fixes and Finishes
A finish does a number of things. It protects the wood from stains and wear, preserves it from the effects of sunlight and moisture if it’s exposed, enhances it to bring out color and grain patterns, and can even alter it by hiding defects or adding color. It does all this by covering the wood with a thin film of resin, made workable with the addition of a solvent which evaporates during drying.
There are essentially two kinds of finishes: “evaporative” and “reactive.” The difference between the two is that evaporative finishes start as a flowable resin and dry as a hardened resin; only the solvent has evaporated. This is not so with reactive finishes, which undergo a chemical change as the film is formed to become an entirely different material.
As far as you are concerned, the difference means two things. First, evaporative finishes can be re-dissolved once they’ve dried by introducing the original solvent. This is what happens every time a new coat is applied, and when it’s dry, the finished film becomes one single layer. (A reactive finish, on the other hand, dries in separate layers.) Secondly, evaporative finishes, because of their tendency to self-meld, are a lot easier to maintain because repairs on them generally don’t show.
What’s the best choice?
Among the evaporatives (which include the time-tested shellacs and lacquers), an easy-to-work-with water-based polyurethane, sold as a polyurethane coating, is at the top of the list. For reactive finishes, polyurethane in an oil base offers the benefits of hardness, adhesion, flexibility, and water-resistance. And though it doesn’t do well over time in direct sunlight, it can be applied easily over stains and existing finishes.
For outdoor things or those in transitionary use, you might consider a clear wood finish, either oil-based or water-borne, such as the kind used on decks and railings. A semitransparent stain also works well in this kind of application because it brings up the natural features of the wood beneath and protects the grain by soaking in and providing some ultraviolet shield in the form of pigmentation.
Since most of the projects in this section of this website are for the indoors, you will probably be considering paint as an option. Enamel paint can provide a smooth, hard, colorful finish that fends off moisture and protects the wood from scuffs and the effects of direct sunlight. For some of the projects, the way paint is applied can highlight certain features and mute others. Decorative treatments can also be painted right on a panel surface to make it functionally attractive.
Inor wood products that have a tendency to absorb a finish, a sanding sealer should be used to prepare the wood before applying paint or stain. Usually, a single coat will be sufficient, and giving the wood a light sanding after it’s applied will bring down any raised grain.
If you plan on staining the wood to bring out its natural characteristics, you’ll have to do that before applying whatever protective finish you choose. There is a confusing array of stains available, and to make matters more confusing, there are colorants such as Japan colors (made with linseed oil), universal tinting colors (pastes that are harmonious with almost any coating), and pigment powders used for touch-up work and making special putties and stains.
But to simplify things, stains can be categorized as either pigment stains or dye stains. The difference is that pigments are mineral particles in suspension within the stain that settle in the pores of the wood and on its surface. Dyes are crystals that are in solution within the stain and only color the wood in a very transparent way. So pigmented stains will enhance the existing grain pattern in a piece of wood, and will even make the surface muddy if applied too thickly. Dyes don’t have that capability, and are able to color without hiding — or improving — the wood’s natural characteristics.
When applying pigmented stains such as wiping stains or pigmented oil or water stains, flood the surface then wipe it off with a rag or sponge. The more you leave on the wood, the darker it will turn out. Don’t restain until the first coat has dried.
With dyes, like penetrating oil stains or penetrating dyes, the process is similar, but the amount left on doesn’t affect color; that’s done by either adding powder to darken it or adding more solvent to lighten it. Color mixing can be done beforehand or in a later application once the first one has dried.