Oil and Wax Finishes

Drying oils

A drying oil cures by reacting with oxygen, turning from a liquid into a solid film inside and on the wood ¹. The two used on furniture:

• Linseed oil (from flax): raw linseed cures very slowly; boiled linseed oil (BLO) contains metallic driers so it cures in about a day. Ambers over time. (The Traditional Paints and Finishes course covers linseed in depth.)
• Tung oil (from tung tree nuts): cures slower than BLO, slightly more water-resistant, less ambering. Many products labeled “tung oil finish” are actually oil-varnish blends; check the label.

Nondrying oils - mineral oil, olive oil, vegetable oil - never cure. Mineral oil is used on cutting boards because it’s inert, but it isn’t a finish; it just soaks in and wears off. Food oils can go rancid.

Applying oil

1. Prepare the surface (see Surface Prep).
2. Flood the oil on with a rag or brush and let it soak for 10 to 20 minutes, keeping the surface wet.
3. Wipe off all the excess thoroughly. Oil left on the surface turns gummy.
4. Let it cure fully, typically a day for BLO, longer in cold weather.
5. Repeat for 3 or more coats, rubbing lightly with fine abrasive pad between coats if needed.

Oil-varnish blends and wiping varnish

Oil-varnish blends (“Danish oil,” many “tung oil finishes”) mix oil, varnish, and thinner. They apply like oil but leave a little varnish in the wood, adding some protection. Wiping varnish is varnish thinned with mineral spirits; it builds a thin film rubbed on with a rag. Both are easy, forgiving next steps up from straight oil ¹.

Wax

Paste wax (beeswax, carnauba, or blends in solvent) adds a soft sheen and a slick feel:

• Apply thinly with a cloth or fine pad, let the solvent flash off, and buff.
• Over oil or shellac, it adds feel and minor protection.
• On its own it’s very thin and wears quickly.
• Wax makes later refinishing harder; most other finishes won’t stick over it until it’s removed.

What oil does and doesn’t do

Strengths: looks natural, enhances grain, feels like wood, simple to apply, easy to renew - just wipe on another coat. Good for chairs, tool handles, and pieces you want to age with use.

Weaknesses: an oil finish is thin and in the wood. It resists water, heat, and stains poorly compared with a film finish like varnish ¹. A wet glass will leave a ring on an oil-finished table. For tabletops, use varnish or at least an oil-varnish blend.

Outdoors, oil on its own weathers quickly; penetrating finishes need renewing every year or two, though they don’t peel like film finishes ².

Safety

Oily rags can spontaneously combust. As drying oils cure they generate heat, and a crumpled pile traps it until the rags ignite - a National Park Service crew’s linseed rag did exactly that ³. Always:

• Spread used rags flat to dry outdoors or on concrete, away from buildings, or
• Store them in an approved closed metal can, ideally under water, until disposal ³.

What to take from this

Drying oils (boiled linseed, tung) cure with oxygen; mineral and food oils don’t. Flood, wait, wipe off all excess, and let each coat cure. Oil-varnish blends and wiping varnish add some protection; wax adds sheen and feel but little durability. Oil looks natural and renews easily but resists water and heat poorly. Spread oily rags flat or seal them in a metal can - they can catch fire.