Here’s a sodium silicate bonded mold that has been filled with aluminum, the silicate bonded sand is rammed up like a conventional green sand mold but is then gassed with carbon dioxide, this hydrolyses the sodium silicate forming a silica bond cementing the sand grains, the two halves of the mold and the core are glued with a silicate glue and I glue kitchen paper over the riser hole.  This means that several molds can be made and put on the shelf for later, the paper stops any creatures taking up residence as the water content of a spider could cause an explosion.

And here’s the finished casting with the pattern that was used to make the mold.  And the best bit is that the riser, sprue and gates that get cut off the casting goes back into the crucible.  I generally leave new castings to age for a week or two before machining them.

This casting is a motor flange for a CNC machine that I am building.

This is the best bit,  after the mold has cooled,  the mold can be broken away from the casting. With the silicate bonded molds I have found that watering the mold and leaving it for an hour assists the shakeout procedure, the casting will still be very hot, wear good quality leather gloves for this and don’t rush at it.  There have been accounts of eager foundry workers dumping a mold with the metal still molten within.