Which of the following is a semi drying oil?

• A. Sesame oil
• B. Coconut oil
• C. Corn Oil
• D. All of the above

Answer: (D)

Oils differ in how they react with air to form a film: drying oils harden quickly, semi-drying oils harden more slowly, and non-drying oils don’t harden at all. This drying behavior tracks with the level of unsaturation in their fatty acids—the more double bonds, the more likely the oil is to oxidize and cross-link.

Coconut oil is highly saturated, so it doesn’t dry to a film. Sesame oil and corn oil both contain enough unsaturated fatty acids to dry slowly, giving them semi-drying properties. So, among the options, sesame oil and corn oil fit as semi-drying oils; the idea of “all of the above” would be incorrect because coconut oil isn’t semi-drying. If you had to pick one, either sesame or corn would be a correct choice for semi-drying oil.