Good question! First, make sure you only mix INTENZE inks together — don’t mix different brands. Mixing brands can lead to unexpected results and makes tracing the cause of those results difficult. Color mixing is best done using ink caps and a stirrer. Dipping your stirrer into distilled water (sometimes mixed a little with witch hazel) in between stirring the inks will lighten them and will also cause the inks to heal a lot lighter than they look when applying them. Our Color Mixing Solution is formulated to boost color mixing. For mixing black inks, our Special Shading Solution is suitable.