Q: I heard that a type of oil known as boiled oil dries quickly. What type of oil is it exactly?

A: Boiled oil is composed of a drying oil to which a pro-oxidant is added, such as metal naphthenate, which is heated to between 100 and 150 ℃ with hot blowing air to accelerate its oxidation. As a result of this process, this type of creates a film that dries quickly. It is often said that oil dries quickly if you simply boil it, however, without the addition of a pro-oxidant, it does not appear to be the case. It is highly likely that many oils labelled as natural coating oils are processed with a pro-oxidant of sorts. We are as yet not sure whether and how pro-oxidants affect human health.