<font color="brown">Okay, this will be my last post on this subject because I don’t want this thread to begin to degrade itself. Also, I need to pack suitcases and plan for a LONG drive to DC since my father won’t fly.
Supergirl, since you already have your books about hair chemistry from college, then there really isn’t a need for me to dig up and copy the structural diagrams about hair chemistry as it relates to relaxing, disulfide bonds, hydrogen bonds, etc. You can just refer back to the info if you want. But no one should expect to rearrange chemical bonds with conditioner . . .
However, I did find some information that I thought would be helpful for anyone who is confused by now! It is not really important for me to be “right” about this, and I don’t want it to appear that we are “at odds.” But I at least want to provide some easily understood information so that people can make up their own minds about what they want to believe about hair care products. Please know that I have the utmost respect for everyone that has contributed to this conversation - - after all the purpose of this forum is to share information, and we have all benefited from each other at some time or another.
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Excerpt from Chapter 3 of
Don’t go Shopping for Hair Care Products Without Me by Paula Begoun (2nd Edition)
CONDITIONER
For all the claims about conditioners penetrating, restructuring, regenerating, and rebuilding hair, they have no ability to do any of that. Conditioners strictly modify the cuticle layer of hair - - temporarily. The scaled layers of cuticle covering the hair shaft need to be held down tight to make the hair feel silky and soft. To that end, conditioners need to “glue” the cuticles down onto the hair shaft or fill in the damaged spaces, to bandage up the tears and breaks in the cuticle that make the hair feel rough and dry. This bandaging is done by ingredients that have an attraction to the cuticle and the ability to bond with it. Cuticles are much like any dead, inanimate surface: Not everything wants to stay put on them. Only certain substances have the physical properties to attach themselves to the unique physical characteristics of the hair.
Why can’t conditioning agents penetrate the hair shaft? Because the whole purpose of the cuticle is to protect its insides, and that means preventing things from getting inside. The cuticle layer and the cortex are there to keep the interior of the hair shaft intact and keep everything else out. Think about it this way: molecularly tiny hair-dye ingredients need a very elaborate, strong chemical process to get the new hair color into the hair shaft and keep it there. It also takes a very elaborate strong chemical process to get your existing color stripped out of the hair’s interior. Hair likes holding on to what it has and it doesn’t want to let anything inside or let out what is naturally inside.
That conditioning agents can’t get inside of hair isn’t a bad thing because they do attach on the surface, where you need them. Conditioning ingredients migrate and cling to the hair’s cuticle layers, helping to shore up what’s there and fill in (temporarily) what might be missing, which is exactly what the hair needs. In order to get as much of the conditioning agents to migrate over, around and under the cuticles, you need to leave the conditioner on the hair for a while so the conditioning ingredients have more time to get where they need to be.
PROTEINS
Proteins are large-chain molecules that cannot be absorbed into the hair shaft. Proteins are often partially hydrolyzed to help them cling better to hair. Regardless, proteins coat the outside of the hair, filling in gaps between the cuticles, which provides protection and a soft feeling. Proteins are a range of ingredients that include plant and animal by-products. Even though proteins are an elemental component of the hair’s makeup, adding protein to hair-care products does not restructure or add to the hair’s composition. To imply that any protein can somehow repair hair or permanently attach to hair is sheer alchemy and fantasy. Ironically, plant proteins, despite their desirability, don’t cling well to hair, at least not as well as the animal by-product alternatives such as collagen or elastin (Hair and Hair Care, Dale H. Johnson, ed.)
Collagen and elastin are proteins that like to cling to hair. They serve several important roles in conditioning the hair. Both nicely coat the outside layer of the hair, filling in the gaps of the damaged cuticle and adding a slight feel of thickness to the hair. Collagen and elastin also have water-binding properties that are delivered mostly to the surface, which is good for the hair.
Collagen and elastin can be broken down with water (hydrolyzed), creating a smaller molecule form that has a better chance of getting in and around the cuticle. (We’re talking a microscopic level of penetration, so don’t get excited or carried away thinking hydrolyzed collagen or elastin will repair your hair or somehow mend it. They won’t. ) Unfortunately, very little of the specially treated collagen or elastin can penetrate and be absorbed, because after they have been hydrolyzed - - partially broken down with water - - they are more prone to being washed away. Hydrolyzed collagen and elastin work best when given time to penetrate a dry or slightly damp hair shaft.
AMINO ACIDS
Hair is made of 22 known amino acids, including cystine, histidine, serine, glutamic acid, tryptophan, and proline. Proteins are assembled from amino acids, and in theory amino acids have a better affinity for hair because they are smaller and have a better chance of penetrating the cuticle layer and providing water-binding properties deeper in. But that’s only in theory. Most cosmetic chemists feel that because amino acids are so small, they are also quite unstable and easy to rinse away, and therefore never get a chance to penetrate and do their thing.
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Before I started doing my clarify, protein conditioner routine after relaxers--my hair never reverted. 
