http://www.dralisyed.com/2008/10/can-relaxed-hair-be-stripped.html
To answer the question--
can relaxed hair be stripped?--
it is necessary that we first understand the chemistry of the hair, as well as the lanthionization (relaxation) process.
When two or more polypeptides align themselves parallel to each other, and their cysteines (amino acid) combine with each other to form cystine or disulfide bonds across these polypeptides, a keratin fiber is created in the process.
Hair, or keratin according to chemical terminology, is made up of polypeptides. (Polypeptides are made up of amino acids -- the basic unit of protein.) Polypeptides are aligned in a parallel fashion and are cross linked with cystine bonds (also called disulfide bonds). Note that cystine bonds have two sulfur atoms.
When excessively curly hair is chemically straightened with hydroxide-based relaxers, (i.e., sodium, potassium, lithium, and guanidine hydroxide, etc.) approximately one-third of the cystine bonds are changed to lanthionine bonds. The lanthionine bond has only a single sulfur atom; one sulfur atom less than the cystine bond of virgin hair.
Lanthionine bonds are very stable, meaning that they are no longer susceptible to further change.
Thus, once cystine bonds have been changed with a relaxer treatment, there is now no way known in science for the lanthionine bonds to be changed back to cystine bonds. In other words, chemical relaxation is a permanent process that cannot be reversed.
Why then do you hear clients saying that their relaxer "didn't take, went back, or reverted"? Or, why do professionals sometimes witness a frizzy appearance on portions of their clients' hair that were previously relaxed? Actually, there are a few explanations.
The first is that the hair was insufficiently straightened in the first place. If, indeed, less than one-third of the cystine bonds were converted into lanthionine bonds, the hair may look straighter on the day of treatment, but will eventually appear to revert. To prevent this occurrence, the proper relaxer strength must be selected and adequate time given to the smoothing segment of the process.
The second possible explanation is that something was done to the hair to roughen-up the cuticle, (i.e., improper shampooing, the use of pH-imbalanced products, incorrect combing, and brushing, etc.). Also, due to the fact that relaxed hair is more porous than virgin hair, humidity can give hair that "less-than-straight" appearance, especially in hot and high humidity climates.
The third possibility is a rare phenomenon, which I call "natural reversion." Although this is a hypothesis and not a documented scientific fact, it is one that has been discussed over the years among some in the scientific community. It has been established that when hair is relaxed, the natural arrangements of atoms and molecules of hair in the space are changed. The "natural reversion" theory purports that this new rearrangement of atoms and molecules in the hair is so stressful and uncomfortable for the hair that it fights to return to its original positions. Therefore, within a week or two, the hair may slightly revert back to its original status i.e. some noticeable reversion.
Keep in mind that even as theorized, natural reversion is a very, very rare occurrence that is experienced by only an infinitesimally small number of people.
By and large, even if relaxed hair seems as though it has reverted, don't be confused...most likely it hasn't.
Since the early 1980's, there have been at least a couple of products that claimed to strip relaxed hair so that it then could be permanently waved. These attempts were not successful. Equally unsuccessful are the mythical "home remedies" of rising the hair with highly acidic substances such as vinegar.
None of these methods have been scientifically proven to work, and they can actually cause damage by ruffling the cuticle and disturbing the charge balance of amino acids and polypeptides of hair fibers.
Should a client ever want to return his or her hair to its natural state, the only way is to cut off the relaxed portion once there is adequate growth. For those who now have a natural head of hair and are not comfortable with the idea of a permanent texture change, it's best to press the hair to achieve straight styles. Pressing is a "physical" alteration that is temporary. Lanthionization is a "chemical" change that is permanent.