Hydrocal Plaster for Scenery, Dioramas, Dentistry and Mold Casting 5 lb Pack Resealable Bag Great for Model Railroads by Capital Ceramics Hydrocal Plaster for Scenery Dioramas and Casting Quick setting, lightweight white plaster in water resistant bag. Ideal for patterns, figurines, commercial casts, and sculpture. It is not for making outer or mother molds, and it is not recommended for outdoor use. Full strength hydrocal gypsum plaster, not cut with cheap plaster fillers Designed for strength and casting detail. Hydrocal is 30% to 40% harder than casting plaster and works much like plaster in mixing, pouring, and setting. Accepts liquid or crystal pigment colors and stains