Tung (Chinawood) Oil
Tung Oil, also commonly referred to as Chinawood Oil, is a high-performance drying oil normally used in small amounts to increase the oxidizing and polymerizing properties of an ink. Tung Oil is so prone to oxidation that metallic driers must be used sparingly, if at all.
Care must be taken when handling Tung Oil, because items such as rags soaked with Tung Oil can auto-oxidize and catch on fire. Tung Oil has a clear-to-light-brown color and a rich, nutty aroma. Normally, only 5 to 10 percent is all that is used in an ink to noticeably boost setting speed and hardness of drying. Tung oil can also be used to increase curing speed and hardness of oil-based air dry overprint varnishes.
Tung Oil has 100% bio/renewables content.
Tung Oil can also be used as a tack reducing agent and will impart flow to stiff-bodied (high-viscosity, low-flow) litho and letterpress inks.
The Tung Oil fruit (right) and the Tung Nut (bottom). Tung Oil (top left) is expelled by crushing the nut.