Calcium Hydroxide Treatment

Calcium hydroxide, a caustic white powder also referred to as slaked lime, is used to treat sewage, manufacture brake pads and even process a traditional Nordic fish dish, lutefisk. But it is also an active ingredient in hair-relaxer treatments designed to chemically straighten naturally curly hair. Not all hair relaxers contain calcium hydroxide, but those that do have somewhat different chemical properties than others.

Identification

Calcium hydroxide is a compound created when calcium oxide is slaked with water or when the aqueous solutions of calcium chloride and sodium hydroxide are combined, according to Absolute Astronomy. Though rare, the compound does occur naturally in some volcanic, plutonic and metamorphic rocks and coal fires. Calcium hydroxide is extremely alkaline; saturated solutions have a pH of 12.4. In addition to its common name of slaked lime, the substance is also sometimes called hydrated lime, slack lime or pickling lime.

Hair-Straightening Options

The calcium hydroxide treatment is just one method used to straighten curly hair, but it represents a middle ground between methods that may be viewed as either not effective enough or too harsh. According to celebrity stylist Ouidad's book "Curl Talk: Everything You Need to Know to Love and Care for Your Curly, Kinky, Wavy or Frizzy Hair," one of the more gentle and common methods of hair straightening is to use a straightening iron. While this does not chemically alter hair, it must be done regularly, which can be time-consuming. It is also impractical for curly hair that's very short.

On the other end of the spectrum, hair relaxers containing lye are also fairly common and can be highly effective. These treatments can permanently alter hairs until they grow out, making them less time-consuming, and they can be performed on short hair. But lye is highly caustic, and with too-frequent or improper use, it can damage hair and even burn skin.

Calcium hydroxide relaxers affect hair in much the same way as lye relaxers, but they are somewhat less caustic. They may not always straighten hair as completely as lye relaxers, but they pose less of a damage risk.

Function

Naturally curly hair is packed with amino acids called cysteines, notes the Cornell Center for Materials Research. These amino acids are connected by disulfide bonds, which physically alter the shape of a hair when they occur in great concentrations, making the hair curl. Caustic hair relaxers work by weakening and breaking these disulfide bonds, capping them so that they cannot re-form later.

Process

Calcium hydroxide relaxer kits vary in their components and prescribed methods, but most include latex gloves, a disposable comb, petroleum jelly, a calcium hydroxide solution, a guanidine carbonate solution, a neutralizing shampoo and a conditioning shampoo, according to Ouidad's book.

When using an at-home kit, you should begin with clean, dry hair. Apply petroleum jelly to the scalp along the hairline to prevent the scalp from burning in case there's any dripping. Wearing the latex gloves, mix the calcium hydroxide and guanidine carbonate to create the activated relaxer, then evenly and thoroughly comb the solution through the hair.

Leave the solution in for the prescribed time, then rinse it out thoroughly with water. Shampoo with the neutralizing shampoo, which will restore a healthy hair pH, and finish with the conditioning shampoo, which will protect the hair in its weakened state. This process is safest and easiest when applied by someone other than the person receiving the treatment, preferably a trained hairstylist.

Warnings

The Food and Drug Administration warns that even though calcium hydroxide relaxers are more gentle than those with lye, they can still burn the skin. To avoid damage, leave the relaxer in for only as long as prescribed, and try to avoid direct contact between the relaxer and the scalp.