Alum is the binding agent used to get paint to stick to whatever is being marbled on ~ paper, fabric, wood, or other porous materials. It comes in powdered form and is mixed with water to create a liquid application.

Instructions for making alum is included (bottle, gloves, and sponge pictured are not!). Please note that alum is an irritant and gloves should be worn to protect your skin from drying out or from rash.