With regressive and modified progressive staining, a differentiator is used. If the differentiator is made in-house, there is the potential for it to be either too weak or too strong. Both scenarios will impact staining. If the differentiator is stronger than intended, it will remove more hematoxylin and will make the nuclei pale. Time is also important. Too much time in a properly prepared differentiator will also remove more hematoxylin and will ultimately under stain the nuclei.