The finish is the last thing a piece receives and the first thing anyone sees and touches. It sets the colour, the sheen and the feel, and it decides how the surface copes with spills, sunlight and handling. There are four main kinds, and within each the choice comes down to how much durability you need and how much work you want to put in.
Penetrating oils
Linseed, tung oil, Danish oil and hardwax oil soak into the wood and harden inside it. The surface looks natural, with no film on top, and it feels like wood. Oils bring out the grain and deepen the colour.
- Boiled linseed oil is cheap and traditional. It darkens the wood to a warm amber. It cures slowly, taking several days, and needs renewal every year or two.
- Pure tung oil cures harder and more water-resistant than linseed, but takes many thin coats and a long cure.
- Danish oil is a blend of oil and varnish, and cures faster. It builds a light sheen after two or three coats.
- Hardwax oil combines oil and wax, for a durable low-sheen surface on floors and tabletops.
Application is by wiping on, waiting a few minutes and wiping off the excess, then leaving the piece to cure. Oil is easy to repair: a worn patch is wiped with more oil, and blends in. Its durability against heat and liquids is lower than film finishes.
Film finishes: varnish and polyurethane
Varnishes and polyurethanes form a clear film on the surface. They seal against water, heat and scratches much better than oil.
- Oil-based polyurethane is durable and slightly amber, and gives a warm look. It takes several hours to dry between coats.
- Water-based polyurethane dries clear and fast, and does not yellow, which suits pale woods and painted pieces. It can raise the grain, and needs a light sand after the first coat.
- Wipe-on polyurethane is thinned, and applied with a cloth. It is forgiving, with no brush marks, but needs more coats.
Apply thin coats, sand lightly between coats with a fine grit such as 320, and wipe off dust. Three coats are typical for a table. A film finish is the choice for tabletops, bar tops, and anything that will see water and daily use.
Shellac and lacquer
Shellac is a resin dissolved in alcohol. It dries fast, in minutes, and gives a warm glow. It is an excellent sealer under other finishes and blocks the blotching on pine and cherry. Its weakness is alcohol and heat, which mar it, so it is best for decorative pieces, frames and as a first coat.
Lacquer dries extremely fast and builds a smooth, hard film with sprayed coats. Aerosol lacquer is the convenient form for small pieces. It is used in professional furniture finishing for speed, and can be repaired by melting new coats into old.
Wax
Paste wax gives a soft, low sheen and a silky feel. It is a light finish over bare wood or over a cured oil, and is easily renewed. It gives little resistance to water. It is often used as a final coat over another finish to add smoothness.
Stains, dyes and paint
Stain adds colour, and is followed by a clear finish.
- Oil-based stain penetrates slowly and gives a forgiving, even colour, but can blotch on pine and maple.
- Gel stain sits on the surface, and is used on difficult woods, giving more even colour.
- Water-soluble dye is vivid and transparent, with no blotching; it raises the grain and needs a wipe of water before the dye and a light sand.
- Milk paint gives a matte, chalky, antique finish. It can be sealed with wax or oil.
Matching finish to use
| Piece | Suggested finish | Reason |
|---|---|---|
| Dining table | Water-based or oil-based polyurethane | Resists liquids |
| Coffee table | Wipe-on polyurethane or hardwax oil | Durable, easy to repair |
| Shelf, bookcase | Danish oil or shellac plus wax | Low use |
| Cutting board | Mineral oil and wax | Soaks in, easy to refresh |
| Outdoor furniture | Exterior varnish, penetrating oil | Weather resistant |
| Toy, small box | Shellac or hardwax oil | Quick, light |
| Painted piece | Primer, paint, then clear coat | Even colour |
The finishes database lists sheen, dry time, application method and durability for sixteen finishes, so you can compare them side by side. The finish tool takes a description of the piece, the wood and its use, and recommends one with application steps.
Preparing the surface
Finish shows every scratch. Sand through grits, 80 or 100, 150, then 180 or 220, and stop at 220 for most work. Finer sanding closes the pores of the wood and stops oil and stain from soaking in. Wipe off the dust with a cloth or tack cloth. Raise the grain by wiping with a damp cloth, let it dry, and sand lightly before the first coat, if you use a water-based product.
Woods that blotch
Pine, birch, maple and cherry have an uneven density, so stain soaks in patches and shows dark blotches. A pre-stain conditioner, or a thin coat of shellac, evens the absorption. Gel stain avoids the problem. Oak, ash and walnut take stain evenly, and the woods database notes which species blotch.
Fixing problems
| Problem | Cause | Fix |
|---|---|---|
| Sticky surface | Coat too thick, cold room | Wipe with solvent, recoat thinner |
| Brush marks | Finish dried too fast | Thin slightly, use a wipe-on |
| Bubbles | Shaking the can, brushing too fast | Stir, brush slowly |
| Rough surface | Dust or raised grain | Sand lightly between coats |
| Blotchy stain | Uneven density | Conditioner or gel stain |