A scalp bleach is where the colour of the hair is changed all over, from the root right through to the ends. The hair will be one consistent colour all over, though it may be toned through the ends to create some variance. If you have hair that is darker and you want to go lighter, a scalp bleach is going to be the option for you.
You will have to have bleach applied throughout your hair, so make sure it is in good condition first. Use conditioning treatments and don’t overdo it with the straighteners ahead of your appointment. Your stylist may be able to use a more gentle colouring technique, but bleaching is always going to be quite harsh.
You will probably need your roots touching up every few weeks to keep your colour fresh. It’s important you do this to keep the colour looking good and to make the colour change worthwhile.