Ortho Stone is a fine bright white dental stone recommended for orthodontic casts and working models. Ortho Stone has exceptional strength which allows it to be used as an excellent working model that is resistant to abrasion and fracture while producing smooth model surfaces. Ortho Stone has minimal setting expansion providing precise, accurate reproduction of detail. Ortho Stone has additional additives that produce a pure bright white product that is essential in orthodontics. Set time of 9-11 minutes with an expansion of 0.095% @ 2 hours and a compressive strength of 11'700psi when dry.