How to Pick Tung Oil Finishes
Some handy tips for IDing and using tung oil finishes plus a list of products
• Why use it?
Among natural finishes, tung oil—an extract from tung-tree nuts—surpasses shellac and linseed oil in hardness, durability, and water resistance. It’s also food-safe, once cured.
Pure tung oil takes two to three days to harden, and needs at least five coats. Oil/varnish blends and wiping varnishes are faster-drying, more practical options, but such terms rarely appear on labels. For help picking a finish, see below.
• How to ID a tung oil finish
Penetrating tung oil finishes come in three varieties: pure tung oil, oil/varnish blends, and wiping varnish. They all share the benefits that tung oil imparts to a finish—durability, water resistance, resilient hardness, and color stability—depending on how much of the oil they actually contain and what form it takes.
Pure tung oil is easy to identify because it contains no solvents. That may be a good thing in terms of limiting your exposure to VOCs, but applying it is an exacting, drawn-out process. You have to wait at least two to three days for each coat to harden. And it takes five to seven coats to get a protective film. Rushing the process, or applying too thick a coat, causes wrinkling, which has to be sanded off. Regular reapplication is a must—“once a week for a month, once a month for a year, once a year ever after,” as the saying goes. The results can be gorgeous, as long as you have the necessary patience.
Oil/varnish blends and wiping varnishes were created to speed up these poky drying times and make application less fussy. Both types do this by adding man-made resins and solvents to keep those resins in solution. If you see “contains petroleum distillates” on the label, then it’s one of these finishes.
The difference between these two is subtle. Blends consist of an oil (or oils) mixed in with a varnish. (A varnish is made by cooking resins in a hot oil until resin and oil form a chemical bond.) Wiping varnishes are just what the name implies—straight varnishes that have been thinned enough to be wiped on with a cloth. All the oils in a varnish are bound up in the resin.
Unfortunately, the terms “oil/varnish blend” and “wiping varnish” are seldom used by manufacturers to describe their tung oil products. The easiest way to tell them apart is to read the application instructions. If they say to wait a certain number of minutes after you put the finish on, and then to wipe up or buff off the excess, it’s a blend. (If you don’t wipe up the extra oil, it will wrinkle and have to be sanded off.) If the instructions don’t call for a follow-up wipe, then it’s a wiping varnish, which dries smooth and hard all on its own.
In short, go with an oil/varnish blend if you want the soft luster of an oil and a faster drying time. Choose a wiping varnish for its ease of application and high durability.
Here’s a list of products that fall under those categories.
Tung oil wiping varnishes
Tung oil/varnish blends