Step 1: Step 1: Deciding if home thermal reconditioning is right for you..
There is also a risk, as with any chemical hair treatment, that it could go poorly. Whether you are still deciding or know you want to do this, DO A TEST PATCH. Part of a thermal recondition is a thio relaxer, which can cause hair problems if your hair has been previously treated with chemical relaxers or dyes. When I did this, all of my hair had been processed with a sodium hydroxide relaxer except for a few inches of new growth, and I had no problems. But then, I have hair like rock climbing cables.
Hair type is also a consideration. I have multiethnic hair, and so many thermal treatments are not suitable for my hair. For this instructable, I used Rusk Thermal Str8, which is formulated to work on any type of hair. These days, I use One N Only Brand Thermal Ionic, Resistant formula, which is available at practically every Sally Beauty for ~$25. I recommend trying a test patch of ONO first to see if it works for you, as it is about a third of the cost of the Rusk stuff.