Curl Chemist for NaturallyCurly.com, Tonya McKay Beckeer, compares the two...

Both types of oils are found in various hair care products, and coconut oil is quite often used in homemade treatments, as well. The superior properties of natural oils are frequently lauded, so it should be interesting to review a few scientific comparisons backed by data.

Water in - water out

Several published studies have summarized experiments done to evaluate and compare the emollient properties of mineral oil, coconut oil, and to a lesser extent, olive oil and safflower oil. In one paper, researchers reported using an analytical technique (dynamic vapor sorption, for those curious) to measure and determine the moisture diffusion coefficient for mineral oil, coconut oil, and other oils when applied to hair. They were interested in finding out was how much water vapor can penetrate into or diffuse out of hair that has been coated with oil.

The data obtained in the experiments revealed that both coconut oil and mineral oil form a protective barrier that effectively prevents the diffusion of moisture out of the hair in low-humidity environments, thereby improving moisture retention and minimizing dry, fly-away hair. All of the oil-treated hair samples showed this effect, whereas the untreated control remained unchanged.

It was noted that for coconut oil, the moisture-retention effects dissipated significantly over time. This is credible evidence that coconut oil absorbs into the hair shaft while mineral oil remains on the exterior surface. (Remember this—it will be important later).

Curl Formation and Clumping

Both coconut oil and mineral oil enhance clumping of adjacent hair strands. This mechanism aids in curl formation, definition of curl pattern, and curl retention. Capillary adhesion, the mechanism by which this is possible, occurs when oils form sufficiently thick films on the surfaces of hair strands and capillary forces between adjacent hairs attract them to one another, effectively binding them into clumps.

Researchers found that capillary adhesion between hair fibers remains constant with mineral oil, but is found to decrease over time with coconut oil, olive oil, and sunflower oil. The reason for this is that the very non-polar mineral oil molecules remain on the surface of the cuticle of the hair. In contrast, the saturated or mono-unsaturated fruit and vegetable oils in this study slowly penetrate into the cell membrane complex (CMC) and are transported into the hair shaft. As this diffusion occurs, the film thickness on the surface of the hair gradually decreases, which diminishes capillary forces. As a result the cuticle scale structure begins to dominate the behavior of the surface of the hair once more, and subsequent tangling and frizz can occur.

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