Finishes

Waxes are rarely used as a finish on their own. Instead they are often applied as a polish on top of other finishes like shellac or polyurethane. Common options include paste wax (a mix of wax and solvent) or beeswax. 

Types of wax:

• Beeswax is a soft wax secreted by bees for comb building and was historically the primary wax for woodwork

• Carnauba wax comes from palm leaves and is the hardest of the natural waxes

• Candelilla, from a desert plant found in northern Mexico and southern Texas, is often used in blends because of its low cost and compatibility in mixing with other waxes

• Paraffin refined from petroleum is a very soft wax that's often blended with harder waxes to make them easier to apply.

True oils, sometimes called “drying oils,” include tung oil and linseed oil. These finishes are widely available, inexpensive, and easy to apply–simply wipe on, allow to soak in, then wipe off any excess before leaving to cure. True oils change from a liquid to a solid through polymerization, a process that strengthens the cured finish. They keep the wood looking natural, but are only moderately resistant to water, heat, and chemicals, and offer very limited protection from wear and scratches.

• Linseed oil is available in several forms. Unrefined, it’s called raw linseed oil, which is rarely used on wood because it dries so slowly. “Boiled” linseed oil has heavy metal additives to speed up the drying time. 

• Tung oil is derived from the nuts of trees that are native to Asia but have been cultivated in other parts of the world. Tung oil is available in a pure, unrefined form and in a heat-treated or polymerized form. The heat-treating process makes the oil a bit more durable and speeds up the drying time. It also minimizes a tendency of tung oil to “frost” (dry to a whitish, matte appearance). Tung oil is paler in color and has better moisture resistance than linseed oil.

Hardwax oils recently made the leap from the flooring industry to the world of fine woodworking. They promise a durable finish with easy, fool-proof application. They contain some combination of plant-based oils (typically tung and/or linseed oil but also sunflower, safflower, soybean, thistle, and others) and one or more waxes (carnauba, candelia, and beeswax among them). Some products also include hardeners and other chemicals, meant to add durability and protection and decrease drying time, with corresponding health and safety implications.

Examples include:

• Rubio Monocoat

• Osmo Polyx-Oil 

• Tried & True Original Wood Finish

• Odie's Oil

Varnishes are made of tough and durable synthetic resins that have been modified with drying oils. Labels on cans of varnish list resins such as alkyd, phenolic and urethane, and the oils include tung and linseed, as well as other semi-drying oils such as soybean and safflower. Varnish cures by the same process as true oils — polymerization — but the resins make this finish more durable than oil. In fact, oil-based varnish is the most durable finish that can be applied without specialized equipment. Varnish surpasses most other finishes in its resistance to water, heat, solvents and other chemicals.

The type of resin used in the varnish determines the characteristics of the finish. Alkyd varnish is the standard all-purpose interior variety with decent protective qualities. Phenolic varnish, usually made with tung oil, is predominantly for exterior use. Urethane varnish, also called polyurethane, offers a better resistance to heat, solvents and abrasions than any other varnish.

Varnish is hard to apply (brush marks, sags, runs, and a magnet for dust) but offers enormous protection. Oil is easy to apply (simply wipe on and wipe off), but offers minimal protection. Between these two extremes lie wiping varnishes and oil/varnish mixes, which combine properties of both. 

https://www.finewoodworking.com/project-guides/finishing/the-confusion-over-wipe-on-finishes

Shellac is a traditional finish made from a natural resin secreted by the female lac bug on trees, mostly in India and Thailand. The secretions, in the form of cocoons, are gathered and eventually refined into dry flakes, which are then dissolved in denatured (ethyl) alcohol to make a usable finish. It can be applied in a thin wash coat for a satin look and minimal protection, or built up and buffed to a full French polish mirror sheen. 

Shellac is available premixed in either clear or orange (amber) formulations, or as flakes that you mix yourself with denatured alcohol. Flakes have more color options, and you have control of the “cut,” or dilution of the finish. 

Shellac naturally has wax in it, but it is also available "dewaxed." This version has the helpful property of being compatible with nearly any other finish. Shellac sticks to (almost) everything, and (almost) everything sticks to shellac. It is often used a "sealing" or "sanding" coat before applying paint or other finishes. 

Lacquer is a favorite of professional shops with spray equipment and ventilation. It is quick-drying, durable, and imparts depth, richness, and shine to wood. Downsides include a tendency to chip and to yellow with age. Variations include nitrocellulose, acrylic lacquer, and catalyzed lacquer. 

Waterborne finishes contain some of the same ingredients as varnish and lacquer — notably resins like urethane, alkyd and acrylic — but many flammable and polluting ingredients have been replaced with water. The chemistry in this product is complex. Because the resins don’t have a natural affinity for water, they must be chemically modified or forced to combine with water.

Waterborne finish is usually made with either an acrylic resin (sold as water-based lacquer) or an acrylic urethane mixture (sold as water-based polyurethane). As with varnish, the addition of the urethane makes the resin tougher and more scratch resistant, but water-based urethane does not have the same solvent and heat resistance as its oil-based counterpart.

Paint is often left out of discussions of wood finishes, but it is a great option with tons of historical precedent. In terms of protecting wood and minimizing wood movement, it’s hard to beat. Milk paint and oil paint are finishes that wear beautifully, don’t look plastic-y, and allow grain texture to show through the color.

Mineral oil is a food-safe substance (you may have seen it sold in drug stores as a laxative) that never cures or hardens, so it offers minimal protection. The idea is that this harmless, innocuous substance penetrates the wood and remains there, helping to drive out moisture and preventing bacteria from getting into the wood and breeding. Mineral oil just stays somewhat “wet” and needs to be recharged and replenished from time to time.

Soap finish is traditional in Scandinavia, particularly on floors. It doesn’t offer much protection, but it is safe and easy to apply, easy to repair, and wears into a beautiful surface with time and use. Not convinced? Read Chris Schwarz’s argument for finishes that look great in the long term. 

Shou sugi ban is a traditional Japanese process of charring cedar on the surface to confer the practical benefits of resistance to water and fire. Japanese cedar is hard to come by, so North American softwoods like Southern cypress, Western red cedar or basswood are good alternatives, or even common domestic species like pine, maple, oak, cherry, and walnut. See burn tests on various species of wood here.

Using a propane weed burner for larger projects, or a propane torch for smaller ones, hold the flame to the wood until it is charred the desired amount. Deeper charring results in a deep black look with an alligator skin texture, and lighter charring brings wood grain to the surface for an attractive rustic effect. Work outside (duh), and keep a bucket of water nearby. Brush off the soot with a stiff brush. While the wood is still warm, apply a coat of wax, oil, or an oil/wax mixture, then wipe off the excess with a rag. The rag will end up covered in soot, but the surface stops transferring black marks once the finish dries.

Nothing. Available everywhere. Makes a reasonable finish for some woodenware. No application time. No dry time. Nontoxic. No PPE required. Free.