If you are inexperienced, it is recommended that you buy the dyes already prepared, or that you go to a hairdresser if you want a specific shade. But if you dare to try at home with professional dyes, we will give you some information that will help you to know the right steps to take:
Proportions. Most professional dyes use a 20-volume oxidant or hydrogen peroxide. Depending on the brand, the box may indicate a ratio of 1+1 or 1/1 between dye and oxidant, or 1+1.5 or 1/1.5, which means 60 g of dye and 90 g of oxidant.
Accuracy. It is important that you prepare the exact doses so that the result is as expected; to do this you can buy a measuring device or a dosing device. It is advisable to start with shades similar to your hair colour (especially if you don't have much practice), and vary the shades as you gain experience.
Root. You have to start applying the dye from the root, working your way down the length of your hair, and leave it on longer where you have grey hair (usually between 20 and 40 min. maximum). You should always place an old towel over your shoulders so that it doesn't stain your clothes.