How to Choose the Best Wood Finish
For many woodworkers and DIYers, finishing is often the most dreaded step of a furniture project. A lot of the information available on this topic is conflicting or overly complex, so we’ve put together a comprehensive guide to help you select the perfect finish for any woodworking project. To keep things simple, we focus only on finishes for indoor furniture.
Finishes can generally be broken down into the following categories:
- true oils
- wiping varnishes
Each offers different levels of protection, durability, and aesthetic. There’s no perfect finish that excels in every category, but there are finishes that work better than others for certain circumstances and for certain furniture projects.
Boiled linseed oil and tung oil make up the bulk of true oil finishes on the market. These are both drying oils, which means they change from a liquid to a solid state through polymerization. Most of these oils have been heat treated and have had chemicals added to speed up the drying time — this is what separates true oils from raw oils, which are rarely used as a furniture finish.
True oils are great because they’re easy to apply: wipe on, let the oil soak into the wood grain, and wipe off. True oils enhance the natural look of wood, giving the grain a warmer and richer look and feel. Another great thing about oil finishes is that they can be quickly and easily reapplied if necessary.
Apart from pure oils, which are rarely used as finishes, these oils build up minimal protection and are thus best used for projects that won’t see heavy wear to their finished parts. Furniture and projects that are best suited for oil finishes include: chairs, shelves, and picture frames. Since these finishes don’t build up a protective film that has potential to chip or flake off, they’re also a good choice for food preparation stations like butcher block countertops and end grain cutting boards.
Varnishes are mixtures of drying oils and resins that leave tough surfaces capable of withstanding moderate to heavy wear. Like true oils, varnishes cure through polymerization, but their relatively high resin concentration makes the surface they leave behind much more durable. Most varnishes for interior applications use one of two synthetic resins, alkyds or urethanes. Alkyd-based varnish is a general purpose varnish, suitable for most situations. Urethane-based varnishes, more commonly referred to as polyurethane, offers additional protection against wear, heat, and water.
Applying a varnish requires some patience, as it can be a time consuming process. Before varnish is applied it’s best to apply a sealcoat. For your sealcoat, you can use a 1:1 ratio of varnish and mineral spirits or simply use dewaxed shellac. Once your sealcoat has dried, brush on your first coat of varnish. It takes around three to five coats to build a durable, lasting film finish. Let each coat dry overnight and sand with a high grit paper (320-400) in between coats until any nibs or surface imperfections are removed. Furniture and projects that are best suited for wipe-on varnishes include: tables, bar tops, and bathroom cabinets.
Oil-based wiping varnishes are a mixture of oil and resins that are intended to be–spoiler–wiped on. They’re one of the most popular finishes on the market today with good reason: they offer superior protection than traditional oil finishes, while still bringing out much of the wood’s natural beauty. They also don’t need to be reapplied as often as a traditional oil finish. Though they offer slightly less protection than a true varnish, the protective coat is easier to control and less likely look like plastic in the end.
These finishes are more time consuming to apply than traditional oils. Each coat applied builds upon the last, offering a greater level of protection. It’s best to start with a heavy coat followed by subsequently lighter coats, sanding with high grit paper (320-400) in between until the desired result is reached (typically 4-5 coats). We recommend both Minwax Wipe-On Poly and Waterlox.
Furniture and projects that are best suited for wipe-on varnishes include: tables, bookcases, and cabinets.
While most people think of shellac as a furniture or nail finish, it’s actually a natural resin produced by the female lac bug. After processing, shellac is either dissolved in denatured alcohol and sold premixed, or sold in a variety of colors as dried flakes. Whether you buy flakes or premixed cans, there are two main types shellac to be aware of: waxed and dewaxed.
Waxed shellac is more common and won’t often be labelled “waxed”, however dewaxed shellac will be labelled “dewaxed.” Waxed shellac is less resistant to water than dewaxed shellac and doesn’t bond to other finishes well. Due to this, it’s best used on its own. Dewaxed shellac is commonly referred to as the “universal sealer” because it bonds well to other finishes and makes an excellent sealcoat. Many woodworkers use colored shellac as a sealcoat since it allows them to alter the color tone or warm the appearance of their wood before applying a topcoat.
Since the solvent in shellac is denatured alcohol, it evaporates and dries incredibly fast. However, because shellac is a solvent-based finish, subsequent applications will run the risk of redissolving some of the shellac that’s already been applied to the project. Minimize this risk by applying thin coats each time without lingering in one area for too long.
Here’s a trick to check if the shellac has adequately dried and your project is ready for another coat. Alcohol evaporates via an endothermic process, meaning it absorbs energy as heat from its surroundings. When you think you’re ready to apply another coat, touch your project. If it’s cold, that means the alcohol is still evaporating and you need to wait a little bit longer.
Lacquers come in three main varieties: nitrocellulose, CAB-acrylic, and catalyzed. Nitrocellulose lacquer is the most common type that you’ll find at most home centers. It makes for a great finish, but has a tendency to yellow as it ages, so avoid when working with lighter colored woods. CAB-acrylic lacquer uses acrylic resins that dry “water white.” This is a good alternative to nitrocellulose lacquer when using a lighter wood since it won’t yellow over time. Catalyzed lacquers use chemical catalysts to speed up the curing process. You can buy them pre-catalyzed (catalyst already added) or post-catalyzed (add when finishing).
While lacquers make fantastic finishes that many woodworkers swear by, they’re not nearly as forgiving as other finishes. Lacquers require a bit of an upfront cost as they’re best applied with a spray gun. Also, since lacquers dry rapidly, they’re prone “blushing” when applied in humid environments. Blushing occurs when water becomes trapped in the lacquer film as it dries, resulting in a cloudy surface.