Mixed hair dye is only good for about one hour.
Once you combine the developer and color cream, a chemical reaction begins. This reaction is what allows the dye to deposit color onto your hair. However, after approximately an hour, the pigments in the dye degrade and become ineffective. This means the dye will no longer provide the desired color or coverage.
It's crucial to apply the mixed dye to your hair immediately to achieve the best results. Avoid mixing the dye until you are ready to use it. If you have any leftover dye after an hour, discard it; it cannot be saved for later use. Applying old mixed dye will likely result in poor color payoff and may even damage your hair.
