Why finish wood at all
A finish does several jobs. It slows moisture exchange, protects against stains and wear, and shows off the grain. Bare wood is not always a problem, since many pieces for dry indoor use are left unfinished, but it picks up marks and moisture easily. The right finish depends on how the piece will be used, how you want it to look and how much effort you want to put in.
Safety comes first with finishes. Many contain solvents or other chemicals. Work with good ventilation, away from flames, pilot lights and sparks. Wear gloves and eye protection, follow the container’s instructions, and consider a respirator rated for organic vapors where the label calls for one. Rags soaked with some oil finishes, especially drying oils such as linseed, can heat up as they cure and may ignite on their own. Spread used rags flat outdoors to dry, or soak them in water in a sealed metal container, and follow local disposal rules. This is a real fire risk, so see the article on workshop fire safety.
Three broad families
Finishes fall roughly into three groups: those that soak in, those that sit on the surface as a hard film, and those that are a soft coating buffed on top. Many products blend features, so check the label of whatever you buy.
Oils
Oil finishes soak into the wood. Some, called drying or curing oils, harden slowly within the fibers, while others stay softer. Many commercial “oil” products are blends that include other ingredients to speed drying or add protection.
Look and feel: A natural, low-sheen appearance that brings out grain and color, often deepening the tone. The surface feels like wood.
Protection: Moderate. Oil resists some moisture and makes the wood easier to clean, but it generally offers less protection against scratches, heat and spilled liquids than a hard film. Some are food-safe once cured, but you should check the product’s own claims rather than assuming.
Effort: Easy to apply with a cloth, brush or pad, forgiving because there is no brush-mark problem, and simple to repair locally. Several coats may be needed, with wiping off of excess so it does not stay tacky. Cure times can be long. It usually needs refreshing over time, especially on surfaces that get use.
Good for: Tables, chopping boards (with a suitable product), tool handles and pieces where a natural feel is wanted.
Waxes
Wax is a soft coating of natural or synthetic waxes, applied with a cloth and buffed to a soft sheen.
Look and feel: A warm, smooth, satin look and a silky touch.
Protection: Light. Wax repels a little water and reduces friction, but wears off easily and does not stand up to heat, standing water or solvents. It is mostly used over another finish or on pieces with little wear.
Effort: Easy to apply and renew, and it is simple to rewax a worn spot. The cost is frequent maintenance.
Good for: Decorative pieces, picture frames, and as a top coat over oil or sealer to add feel and a little extra protection.
Varnishes and film finishes
This family includes varnish, polyurethane, lacquer and shellac, which form a layer on the surface. They differ in chemistry, drying time and repair, but share the idea of a protective film.
Look and feel: Anything from matte to high gloss, depending on the product. The surface can feel somewhat plastic compared with oil, though thin coats feel more natural.
Protection: Generally the highest of the three families against wear, moisture and stains. Quality, thickness and product type matter. Some are intended for exterior use with ultraviolet protection, others for interior use only.
Effort: More demanding. You need clean, dust-free surfaces, careful application to avoid runs and bubbles, light sanding between coats, and longer drying times. Repairing a damaged film often means re-coating or stripping a whole area rather than a spot.
Good for: Tabletops, floors, doors, window frames and anything exposed to moisture or heavy use.
Comparing at a glance
| Aspect | Oil | Wax | Varnish-type film |
|---|---|---|---|
| Typical look | Natural, in-the-wood | Soft satin | Matte to gloss, on the surface |
| Typical protection | Moderate | Light | Highest of the three |
| Ease of application | Easy | Easy | More demanding |
| Ease of repair | Easy, local | Easy | Harder |
| Maintenance | Periodic re-oiling | Frequent | Occasional recoat |
These are broad tendencies, not guarantees. Individual products vary a lot.
Preparing the surface
Finish shows every flaw, so preparation matters.
- Smooth the surface. A sharp hand plane or scraper may leave a finer surface than sanding, as described in the overview of hand tools. Sand with progressively finer grits and go with the grain, since cross-grain scratches show up under finish.
- Remove dust. Vacuum and wipe with a barely damp cloth or tack cloth, and control dust in the shop, since particles settle into wet finish. See the article on workshop dust.
- Remove glue residue, which blocks finish and shows as pale patches. Joints with squeeze-out left behind are a common culprit.
- Test first. Try the finish on an offcut of the same wood. Different species take finish differently, and testing shows the final color before it is on the real piece. Hardwood and softwood can look quite different under the same product.
Choosing for a project
- A dining table: a hard-wearing film or a durable hardened oil product, since spills and hot dishes are likely. Check the label for heat and water resistance.
- A bookshelf or decorative box: oil or wax, for a natural look with little wear.
- A chopping board or wooden utensil: a product marked as suitable for food contact by its manufacturer. Check the label.
- Outdoor furniture: a finish designed for exterior use, plus acceptance that outdoor finishes require periodic renewal. Wood left outside will weather in any case.
- A child’s toy: look for products labeled as suitable for toys under the rules of your area, and allow full cure time before use.
Applying evenly
Thin coats beat thick ones for nearly every finish. Follow the label for number of coats, drying time and sanding between coats. Apply in good light, keep the edge wet as you work to avoid lap marks, and stop fiddling with a coat once it starts to set. Temperature and humidity affect drying, so avoid very cold or damp conditions.
Maintenance
Finishes age. Oil needs reapplying when the surface looks dry or water no longer beads, wax needs renewing as it wears, and film finishes need recoating when they dull or scratch through. Because wood moves with humidity, as described in the piece on wood movement, finishing all sides of a board helps it behave evenly.
No finish is best in every case. Match it to the piece’s use, your tolerance for upkeep and the look you want, test on scrap, and follow the manufacturer’s instructions and safety directions.