You need to pay a special attention on beached, highlighted hair, when having the BKT done. You need to make sure that the hair is healthy enough to get the treatment done. For all types of hair, you need to use a flat iron, to cristalyze the keratin into the cuticle. For double processed bleached hair, you need to make sure that the whole hair is covered by product and you need to lower the temperature of the flat iron a little. Instead using a 450 degress, you need to lower to 400 degress, because this type of hair is fragile and the cuticles are completely open.