How long does it take to stain hydrophilic coatings with Congo red

Two days. First of all, you need to prepare the Congo red dye solution to stand, and then spend two days to use the Congo red on the hydrophilic coating dyeing, because the surface of the hydrophilic coating is not easy to adsorb the dye, so you need to spend two days on the hydrophilic coating with the Congo red two days of dyeing. Congo red is an organic compound for brown-red powder, dissolved in water is yellow-red, dissolved in alcohol is orange.