When marbling, use Alum to pre-treat fabric for clear transfer of designs. One cup of alum is dissolved in water along with four teaspoons of Calgon, to create a solution for submerging the fabric. Wring out the fabric without rinsing and allow to air dry before marbling. Details:Available in multiple sizesAlso used as a mordant with some natural dyesCAUTION: Keep dyes, paints and chemicals away from children. Avoid unnecessary personal contact. Do not take internally.