Methocel (or Methyl Cellulose) is a synthetic gelling agent that provides a viscous surface for marbling on fabric and paper. It is also used in book arts as a paper sizing, for paste papers and to slow the drying time of PVA glues. Compared to natural thickeners, Methocel is more economical and longer lasting. It is a less expensive alternative to Carrageenan.
Stir 4 TBS of Methocel into 1 gallon of warm tap water. Add 1 TBS of clear household ammonia, and stir until mixture is clear. (The ammonia will help the Methocel thicken the water.) For larger quantities, repeat procedure using same proportions. Fill marbling tray to about 1.5" deep and allow it to rest for 30 minutes.