you should probably repost this question in the keratin services thread, or simply poke around there and you'll find your answer.

Your results will depend on a variety of factors.

1. The brand of BKT ( Brazilian keratin treatment) being used. Some of the treatments have high levels of Formaldahyde. The higher the concentration the straighter your results.
2. Technique. The more passes with the flat iron, the straighter your results
3. the state of your hair ( the more damaged the better). chemically treated hair responds better to the treatment.

I'll end by saying that no two people have the same outcome when they get the treatment done. You have to be willing to throw caution to the wind with on this one. The good thing is that most of these treatments wash out within a month or two.