Oil and wiping varnish. When I buy a container of wipe-on finish I typically put a puddle on the top and let it dry so I can determine whether it’s oil or wiping varnish. Oil, or any finish that contains oil, such as Danish oil, wrinkles and stays soft. Wiping varnish dries smooth and hard.
The oil most shrouded in mythology is tung oil. Like linseed oil, tung oil is a vegetable oil that doesn’t harden well. So all the excess has to be wiped off after each coat to get a functional finish.
Beginning in the late 1960s a fellow named Homer Formby began promoting a wiping-varnish finish he labeled “Tung Oil Finish” in TV infomercials and in appearances at antique clubs and stores. He claimed that tung oil, which originates in China, is such a great finish that it was used to protect the Great Wall of China! Come on! The Great Wall of China is made of stone and in its many parts is over 13,000 miles long and high enough to keep marauding tribes out. You have surely seen pictures of tourists walking on parts of it near Beijing. It’s so huge that it can be seen from space.
The idea of people coating this stone structure with oil to protect it is absurd. And the further idea that the oil would hold up for longer than a few months when exposed to the harsh weather in northern China makes this claim even more absurd. So imagine my surprise and exasperation when I read this totally unbelievable claim repeated recently.
Tung oil. The problem with tung oil is that manufacturers often label wiping varnish “tung oil” as McCloskey has done here on the right in contrast to Old Masters on the left. You can tell what the finish is by letting a puddle dry on a non-porous surface or by whether on not a thinner is listed on the can. Wiping varnish always contains a thinner, tung oil doesn’t.