We have found two sizes of very soft, malleable rubber bowls for mixing and pouring plaster. The smaller is approximately 100 mm. in diameter and holds about half a liter; the larger bowl is about 160 mm. in diameter and has a capacity of 0.85 liters. These flexible bowls will squeeze to a point to make a narrow pouring mouth.
*Available separately, our mixing spatula with feather edge is excellent for using with rubber and plastic bowls and beakers (do not use spatula with resins).