The ratio for tint to developer is 1cm tint to 3 drops of developer.
Mix your tint and developer together and apply to the hairs straight away. This ensures the oxidation process happens on the hairs which allows the molecules to penetrate the hair. This results in a stronger bond, a deeper color and a longer lasting tint.
If you allow the tint to oxidize (darken) before applying the tint to the hairs, the hairs will still tint however, the molecules will have swelled too much to be able to completely penetrate the hairs. This means the tint will wrap around the outside of the hair rather than inside.
If you are lifting or laminating, leave tint on for 1-3 minutes.
If you are not lifting or laminating, leave the tint on for 6-10 minutes.