Monday, August 15, 2011

Deep Conditioning

Sounds so nice – deep conditioning for your hair. And yet it seems impossible because hair is not living tissue. You wouldn’t try to deep condition a damaged, old wool sweater, would you? But then we don’t subject our woolens to the same handling we subject our hair.©Science-y Hair Blog 2013

Deep conditioning hair really means several things: softening the hair, bonding compounds to the damaged areas to make hair “hydrophobic” or water-repelling like healthy hair. Deep conditioning is meant to maximize those things which conditioner does for your hair: reducing friction to prevent tangles and resulting breakage from combing and other mechanical damage, sealing in moisture, adding flexibility and softness.
©Science-y Hair Blog 2013
There are several aspects of deep conditioning: product distribution, substantivity (ingredients bond to your hair rather than rinsing off), product penetration into the hair, duration (time of treatment) and use of heat.©Science-y Hair Blog 2013

Distribution: To thoroughly condition your hair, you need good product distribution which means combing or scrunching in a conditioner. When people use shower caps or plastic wraps, they are also improving distribution. Like painting a wall, the coating needs to be both even and thick.
©Science-y Hair Blog 2013
Bonding: Cationic ingredients and proteins bond to your hair, filling in the gaps (porosities) caused by damage and daily handling, also creating a thin layer of lubrication so that your hair is less prone to tangling, easier to comb, and aligns with the neighboring fibers better - which is key to having lustrous (shiny) hair that feels soft.©Science-y Hair Blog 2013

Penetration into hair: Some ingredients have the potential to penetrate into the hair (beyond the outer, cuticle layers) such as coconut oil and Cetrimonium bromide. Another which I do not have research data for, but which has low enough molecular weights (short enough carbon chain) is Cetrimonium chloride. So if your conditioner has any of these ingredients, it already has greater potential to be a “deep” conditioner.©Science-y Hair Blog 2013

Duration of conditioning treatment: I’ve read that cosmetics chemists (those who design hair products) maintain that a product will not do more good if you leave it on longer than stated on the bottle. And yet I find information to contradict this. It’s probably not a good idea to leave conditioner on your hair for hours or overnight because these are products meant to be rinsed off and you may not want some of these ingredients to have contact with your skin for an extended period. That being said, the longer a hydrolyzed protein, a conditioning polymer such as polyquaternium-4 or quaternium-26 or cationic surfactant such as Cetrimonium bromide stays in contact with your hair, the more is adsorbed to the hair and, where possible, penetrated into the hair. So if you prefer to condition for longer than a few minutes, you may benefit. Or you may end up with limp hair. But it will be soft, limp hair! There is a point at which the hair has bound all the proteins and/or conditioners it can and cannot "use" any more. ©Science-y Hair Blog 2013

Heat: Do products which are not designed to be used with heat, work better with application of heat? Possibly. 
1) Heat liquefies ingredients somewhat and this improves distribution, allowing oils (especially "solid" oils like coconut oil or shea butter) to spread and penetrate if they can. If you’re adding heat, you’ve probably wrapped your hair all up, also improving distribution. 
2) Heat speeds up reactions; when ingredients are bonding to your hair, it is a chemical reaction. Heat also creates a very moist environment, all that moisture is there while the hair is swollen from having been wetted, from being in the presence of a wetting agent (conditioner) – so the humidity created by adding (moist) heat is probably beneficial, protecting the hair from water loss during the process.
You can add heat by putting on a heat wrap or wearing a shower cap or plastic covering over your hair, or you can warm your conditioner first. But don't zap it in the microwave - heat some water in a dish and then set your conditioner in a smaller dish, in that bowl of water to heat gently and evenly.
Journal of Cosmetic Science, 56, 323-330 (September/October 2005)
Penetrationon of Cationic Conditioning Compounds into Hair Fibers: A TOF-SIMS Approach
S. B. RUETSCH and Y. K. KAMATH, TRI/Princeton 
Journal of the Society of Cosmetics Chemistry, 43, 259-273 (September/October 1992)
Assessment of the Substantivity of Cationic Quaternary Compounds to Hair by Potentiometric Titration Using the Surfactant Electrode


  1. Not sure if you are familiar with him, but Dr. Ali Syed is a master chemist and founder of a hair care line who has written also on this topic. You may find his journal articles interesting as he does studies on the effectiveness of deep conditioning for long periods of time versus using heat for a shorter time.

  2. This is great info. this blog is SUPER informative/educative. Thanks so much …I have always been confused on conditioners. From now on I will be looking for both Cetrimonium bromide and Cetrimonium chloride on my deep conditioners