The first step in finishing a project (beyond preparing the wood, of course) is to choose the finish you want to use. In fact, it’s wise to make this choice even before starting on the project because it may influence the wood you choose.<\/p>\n
There are seven broad categories of finishes to choose from:<\/p>\n
These seven can be reduced to four depending on whether or not you intend to use a spray gun.\u00a0 For example, there’s no point spraying slow drying varnish because you can get the same qualities with a faster drying finish and avoid a lot of dust nibs.<\/p>\n
So for spraying, limit your choices to one of the faster-drying categories: shellac, lacquer, water-base or two-part finish.<\/p>\n
If you’re going to use a brush or cloth, choose among oil, varnish, shellac and water base. Shellac and water base both dry slowly enough to be brushed as long as you move quickly. Also, “brushing lacquer” can be brushed, of course, if you have some reason to choose this product.<\/p>\n
Wax is not included in these lists because it has such limited use as a finish.<\/p>\n
Now that the choices have been reduced to four, how do you choose among them? There are six characteristics you need to consider. Usually, one or two will totally outweigh the others, so the choice is rarely complicated.<\/p>\n
The six are:<\/p>\n
Appearance<\/strong><\/p>\n There are two broad categories of appearance: how thin or thick the finish appears on the wood, and the amount of color the finish adds to the wood.<\/p>\n All finishes can be applied very thin to produce what is commonly called a “natural wood look.”\u00a0 Consider Danish teak furniture, which is often marketed as having an oil finish but is actually finished with a very durable, film-building conversion varnish. To get a natural wood look with any film building finish, simply thin the finish a lot to reduce the film build and apply two coats — the first to seal the wood and sand smooth and the second to provide the sheen (gloss, satin or flat).<\/p>\n Oil and wax can’t be built up on the wood because they never dry hard. All the excess of each has to be wiped off, so these finishes are entirely limited to producing a natural wood look. All other finishes can be built up thick.<\/p>\n Different finishes add different degrees of yellow\/orange coloring to wood. Most add some amount of yellow\/orange, but water-based finishes and CAB-acrylic lacquer add none. Amber (orange) shellac adds the most color. Oil and varnish are next.<\/p>\n Generally speaking, colorless finishes look great on white woods such as maple and ash, and yellowing finishes are better for bringing out the richness of darker woods such as cherry and walnut.<\/p>\n The differences in the amount of color a finish adds are less apparent when used over a stain.<\/p>\n Protection and Durability<\/strong><\/p>\n Protection refers to water resistanc — ethe degree to which a finish resists penetration of moisture. Durability refers to the strength of the finish film itself to resist being damaged from coarse objects (scratches), heat, solvents, acids and alkalis.<\/p>\n Though the two terms refer to different qualities, the words are often used interchangeably because finishes tend to rate similar for both. For example, polyurethane varnish is both more protective and more durable than nitrocellulose lacquer.<\/p>\n Protection has most to do, however, with the thickness of the film. Moisture has greater difficulty penetrating a thicker film than a thinner film. So four coats of shellac, for example, are far more protective than one or two coats of wipe-on polyurethane (polyurethane varnish thinned half with mineral spirits). But polyurethane is still the more protective and durable finish at the same thickness.<\/p>\n Because oil, oil\/varnish blend and wax can’t be built up, they are too thin to offer more than seconds of water resistance.<\/p>\n To better understand protection and durability, please refer to “How to Choose a Finish: Part II<\/a>.”<\/p>\n Ease of Application<\/strong><\/p>\n The degree of difficulty applying a finish is a big consideration, especially for beginners and woodworkers who don’t do much finishing.<\/p>\n Speaking generally, wipe-on\/wipe-off finishes such as oil, oil\/varnish blend, wiping varnish, gel varnish and wax are the easiest to apply successfully. If protection and durability are big considerations for you, along with ease of application, use wiping varnish and apply many coats.<\/p>\n Any of the finishes that dry slowly enough to be brushed are next in difficulty, with the trade-offs being that varnish has more time to level for reduced brush marking but also more time to collect dust nibs. Shellac and water-based finish (and brushing lacquer) provide less time for brushing and also collect fewer dust nibs.<\/p>\n All the faster drying spray finishes are more difficult to apply because of the more complicated care and adjustment of the spray gun. If you have never used a spray gun and do very little finishing, you would probably be wise to stick with slower drying wipe-on\/wipe-off and brushing finishes. You can get all the same qualities of appearance, protection and durability with these finishes as you get with the spraying finishes.<\/p>\n On the other hand, spraying is not at all difficult, and if you’re willing to devote the time to learn a spray gun, similar to the time it takes to learn woodworking tools, spraying is fast and produces almost perfectly level and dust-free results as long as you’re using a fast drying finish.<\/p>\n Rubbing Qualities<\/strong><\/p>\n Sanding a finish level and rubbing it to an even sheen is the only way to produce a perfect finish (other than French polishing using shellac). With all the finishes other than oil and wax, rubbing qualities are the opposite of the finish’s scratch resistance because rubbing is scratching using abrasives.<\/p>\n By far, the best rubbing results can be achieved with nitrocellulose lacquer. Shellac can also be rubbed to produce good results. Most other finishes are difficult to rub to an even sheen.<\/p>\n