Be prepared for a quite a bit of work when it comes to clean-up after casting. There usually is a little bit of flow out from the seams of the two halves of the sand flask/casting mold - near impossible to get a perfect seal. This might not be a real issue, but a tight seal and good leveling of the contacting surfaces go a long way. If working with very hard metals like nickel and bronze, don't do sloppy work here. One important thing to remember when making your model/plug: Its shapes MUST be able to release between two mating layers.



If you don't want to go about carving in the sand after packing it, I highly suggest putting in a few conical wooden dowels before packing the sand. Minimum of one for pouring, another for venting - more for larger surfaces. Make sure the dowels touch your model when packing the sand.



There are also a large variety of specialty sands, materials and binder materials available, to make the sand molds less fragile. If using these, remember that the sand molds actually need to come apart afterwards.



(Former foundry worker, molding and sand-casting marine prototypes and ornamental figures)