By far the most common finish used when one wants to see the grain of the wood is varnish. While there are other finishes available, varnish has been used literally for centuries. Some modern varnishes are adaptations on the original, but they still qualify as being varnish. Many of these are labeled as “polyurethane varnish” rather than just saying “varnish.”
To understand the differences that these new varnishes provide, we need to have a basic understanding of the chemistry behind varnish. There are three basic ingredients in any varnish: resin, oil and a solvent. The solvent is there to allow the varnish to be brushed on and flow, with the intent that it dissolves. Therefore, it really isn’t all that important. I think we can all trust that the manufacturers will use a solvent that will accomplish the purpose.
It is the other two ingredients; resin and oil that make the difference in varnishes. The types of these ingredients used, as well as the ratio between the two of them, are what give each varnish its particular characteristics.
There are three types of resins used: phenolic, alkyd and polyurethane. In recent times, most varnishes are polyurethane, due to its lower cost, higher scratch resistance and clear coloration. The best (and most expensive) varnishes are made using phenolic. It is also possible that a combination of these resins will be used in one varnish.
There are two types of oils used in varnish: tung oil and linseed oil. Of the two, linseed oil is by far the more common, due to its lower price. However, many people feel that tung oil is a superior product, and it is found in the higher priced varnishes.
The other major distinction to look for in a varnish is the use that it is created for. Most varnish is created for indoor use, where the wood and the varnish on it are protected from weather and ultra-violet light. Spar varnish, sometimes referred to as marine varnish is created specifically for outdoor use. Since any wood left outdoors is much more susceptible to absorbing moisture and expanding, these varnishes have a higher ratio of oil to resin, making them more flexible. They also have UV inhibitors added to the varnish to protect it.
When selecting a varnish, it is important to consider the application; specifically, where the finished item will be used. If it is going to be used outdoors, then you definitely want a spar varnish. If it is going to be used indoors, then the next question is whether it will be subject to a lot of wear. A table top needs a more durable finish than baseboard and casing. Therefore, selecting a hard varnish, with good scratch resistance is important.
Epifanes Clear Gloss Varnish
Man O' War Spar Varnish
Behlen H3983 Rockhard Table Top Varnish
Cabot Satin Spar Varnish #8042
Minwax Fast-Drying Polyurethane
Epifanes is considered by many to be the best varnish around. This is a spar varnish, with UV inhibitors built in. It is made with a combination of phenol and alkyd resins for superior protection. They also use tung oil, rather than the less expensive linseed oil. The best of everything is used in this varnish, to provide the best possible end result. Epifanes also has a number of other varnish products, including one that provides a hand-rubbed appearance.
McCloskey is actually an owned brand of Valspar, who bought them out many years ago. This is another spar varnish, designed for use outdoors. As such, it has the necessary UV protection and flexibility needed to survive the harshness of the outdoor environment. This varnish is made from tung oil, although the manufacturer’s information doesn’t say what type of resin they are using. The only thing we’re sure of is that it isn’t a polyurethane. It adheres extremely well to oily woods, such as mahogany. Available in both satin and gloss finishes.
Rockhard is a varnish specifically formulated for use on tabletops and other surfaces which are likely to receive lots of rubbing. It is very hard, being made of urethane resin, so it resists scratching well. It also resists the damaging effects of water, alcohol, foods, chemicals and detergents. This is an indoor varnish that is not UV protected for outdoor use. Being a hard varnish, it’s not flexible enough for use where changes in humidity would affect it. The low VOC formulation is great for working indoors. Available in both gloss and satin finishes.
Cabot makes another spar varnish, at a lower price than the Epifanes varnish listed above. This one uses alkyd resin. The manufacturer doesn’t mention what type of oil is used in their literature, but based upon the price, I’d say it’s probably linseed oil. Nevertheless, this varnish provides an excellent finish for both indoor and outdoor uses. It is UV protected, and being a spar varnish it is designed to be flexible and handle the effects of weather. It is also available in gloss and semi-gloss.
We couldn't put this list together without mentioning Minwax, the biggest name in varnish and stains. While they don’t produce a spar varnish, they do produce excellent polyurethane varnishes at a reasonable cost. This is an indoor varnish, designed to provide superior scratch resistance. However, it doesn't work as an exterior varnish, as it is not designed for that. Minwax calls this a “fast drying” varnish, saying that it can be recoated in four to six hours. However, many other varnishes can be recoated in the same time, so take that name with a grain of salt.
Before embarking on the current stage of my life, I spent 15 years as a Manufacturing Engineer in both the medical equipment field (medical electronics) and automotive engineering (city transit buses). After that, I owned a small construction company, mostly doing residential remodeling and commercial tenant finishes. I am no longer in either of these fields, but still get my hands plenty dirty as a consummate do-it-yourselfer; working on everything from remodeling my own home to rebuilding my car’s engines. My hobby (when I can find the time) is woodworking; making everything from toilet paper holders, to shelves, to music stands for my own home. My wife long ago gave up the idea that a two car garage is for parking two cars; it is my workshop.
While I cannot claim to having worked professionally with all types of tools, I have worked professionally with some. This comes from my previous careers, where I had to specify, buy and at times live with those decisions. Additionally, I would have to say that my engineering background has given me a thorough understanding of the construction of such tools. So, while I may not have used a particular type of tool personally, I have the knowledge to cut through all the advertising hype and statistics; in order to get at the truth of how well a tool will operate and last.
In my current career as a writer, I've written over 90 books. This includes my own titles and those I've written on contract. I've also written a complete website on how to build your own home.