Procion is a fiber reactive dye that chemically bonds to cotton and can be used in cold water. It is among the most lightfast and washfast of dyes. iDye natural needs heat, 180 degrees for best results. It is a direct dye which is fast and gives very even color, but it is only stuck in the fiber so it is more likely to both fade and wash out. Procion can be used for Ice dyeing and in squeeze bottles for tie dye. iDye natural will turn out very pale in these colder applications.