The Cast-PRO Shaker Dental Stone is a great way to cast footwear impressions. The simple design consists of a large jar of dry dental stone powder and a separate measuring container. Simply fill the measuring container with water and then add the water to the dry dental stone. Secure the plastic lid tightly and vigourously shake the mixture constantly for at least 30 seconds to completely mix. Immediately open the jar and carefully pour the thin mixture into the footwear impression, allowing the mix to gently flow into and across the fragile impression. Allow at least 25 to 30 minutes to set. Compression: 8,500psi. Expansion: .12%.