Oils in Finishing
Learn why certain oils cure better and what makes an oil suitable for finish.
by Bob Flexner
Oil is one of the most important ingredients used in finishing products. Besides being a finish all by itself, oil is an important component in varnishes, polyurethanes and furniture polishes; a primary binder in stains, glazes and pore fillers; a plasticizer in lacquers; and a lubricant used together with sandpaper or abrasive powders to level finishes and rub them to an even sheen.
Despite its importance, oil is poorly understood. To help make sense of it and understand how the various types differ, a little technical knowledge is helpful.
The Nature of Oils
You’ve probably noticed that some oils stay liquid forever while others get sticky after a while and still others dry completely after a day or two. The explanation is that some oils have more reactive sites than others, and it is at these sites that oil molecules crosslink and cure, usually with the aid of oxygen.
Oils that never dry have very few or no reactive sites, oils that get sticky have a few reactive sites and oils that dry completely have sufficient reactive sites to make this possible.
Oils have three large families: mineral oil, vegetable oil and synthetic oil.
From the December 2017 issue, #236