Deep conditioning: Curl definition and Damage?

A specific comment on the original deep conditioning post says that deep conditioning produces excellent curl definition. The panel were presented with  one theory on why this happens ( BBA,pp 210-216,1999). This study suggested keratin changes structure when exposed to water for long. For example a study on nails (same keratin type as hair) showed that protein (keratin) coiled very differently after 15 minutes (saturation point of water). This coiling change led to softening and weakness in the keratin.  The panel were asked



1. Do you think that curl definition associated with deep conditioning could be linked to temporary changes in keratin

2. Do you think it is beneficial or do you think there should be a time limit on water exposure?

Nails and hair have same type of keratin, therefore I think that this link is valid (meaning water changes the keratin pattern). I do not think it is right to avoid water but I do think some regimes can be quite extreme for example leaving the conditioner on overnight. I think repeating this regularly could lead to softer but weaker hair. Weak hair breaks.






"The bonds that link up the polypeptide chains of the hair are hydrogen, salt and disulfide bonds. Hydrogen bonds account for one-third of the hair's strength. The hydrogen bond is a weak physical side bond that is easily broken by water or heat. Hydrogen bonds can be reformed by drying or cooling the hair." Hair recovers from water very well without damage. Source: http://www.texascollaborative.org






I was going to quote a similar fact that Ktani stated regarding hydrogen bonds in hair. They can be temporarily broken by water (hence the various styles we achieve from braiding/twisting while wet), they reform when the hair is dry. However, I believe that these hydrogen bonds are broken when some type of physical change is placed on the hair - typically via styling. I don't agree that DC will yield excellent curl definition by sole application of the product. I do believe that DC can smooth the hair cuticle - this smoothing naturally causes curl definition for some. In the case of some conditioners, more time yields more penetration or deposition onto the hair follicle. I do think there is a point at which using extended time periods to DC your hair is excessive.






I would agree with the responses, especially that hydrogen bonds can be broken by water. It is known that hydrogen bonds make up the amorphous matrix of hair and nails, the above is a valid point. Ref: H.P. Baden et al (1973)






I also think this point is valid and depending on one's hair type conditioner alone does define curls. I pretty much get the same curl definition with water as I do with conditioner, but with conditioner the definition stays longer and curls/waves are elongated, and with water once my hair starts to dry the definition goes away as my hair shrinks. I think using conditioner to define curls can be beneficial for those whose goal is to do so, but I think there should be a time limit and/or care should be taken as to the amount of conditioner used. I believe the conditoner should be diluted with at least 80% water if it's going to be left on the hair for extended amounts of time or used as a styling agent.