There are a lot of complicated terms out there when it comes to shampoos. If you have read any of my books, then you know that the term "sulfate free" is just a marketing term with an unclear meaning. For that reason, I emphasize learning about the details of various ingredients so that you can pick the shampoo that is right for you.
Another set of confusing terms are the words "clarifying" and "chelating" shampoos. Sometimes people use these words interchangeably, but in the purest sense these shampoos are doing two different things:
Clarifying shampoos are best if you have the following issues: oily, limp, hair with lots of product buildup
Chelating shampoos (sometimes called "detox" shampoos)- are best for those who have been exposed to well water (which leaves hard water deposits like calcium or magnesium carbonate on the hair), no-lye relaxers (which also leave the same mineral deposits on the hair as hard water), or for those who have other reasons to suspect that they have mineral buildup. Mineral buildup dulls the appearance of the hair over time and worsens hair breakage.
Here's how you can tell the difference between the two shampoos:
Clarifying shampoos are shampoos designed to remove product buildup. They are best suited for people who feel like their hair is extra oily and limp. For example, if you co-wash your hair routinely, you would likely benefit from using a clarifying shampoo occasionally. Clarifying shampoos work better at product removal because they contain higher percentages of anionic surfactants like sodium laureth sulfate, ammonium laureth sulfate, and even sodium lauryl sulfate. When over-used, these ingredients can make the hair feel really dry. For curly types, overuse can lead to hair breakage. For this reason, in curly hair types these shampoos are only designed to be used occasionally. As the term "anionic" reflects, these leave an overall negative charge on the hair, which can make the hair more prone to breakage if not followed by a heavy duty conditioner.
Chelating shampoos contain ingredients like tetrasodium or disodium EDTA, citric acid, ascorbic acid and other acids to form bonds with mineral deposits and wash them away. Mineral deposits on the hair (like calcium carbonate and magnesium carbonate) cannot be washed away with regular shampoos. Instead, the stick to the hair and can make it difficult for the hair to be moisturized. Because these products typically have high acid content, they leave a positive charge on the hair, which, if you have read my books, almost always leaves the hair feeling softer. For this reason, some people who do not have mineral deposits on the hair may still enjoy the results from regular use of a chelating shampoo.
Clarifying shampoo: negatively charged, heavy-duty surfactants for extra cleansing to be used occasionally and followed by a thick conditioner
Chelating/Detox Shampoo: positively charged, acid (and EDTA) containing ingredients to soften hair and remove mineral deposits