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- #41
The sand I use is referred to as green sand, simply because it does not cure to a hardened state. There are lots of other binder systems out there, but for the home guy, green sand is hard to beat. Basically it is 10-12% bentonite clay mixed with sand, then water is added until the moisture is evenly distributed. The sand won't be so wet as to feel like beach sand, but with pressure it will stick together.
Packing the sand in the flask is called ramming, and it is the part that takes practice to master. What's nice about using green sand is that if you don't like your mold, you just re-do it, and you're not out any binder or sand. Other binder systems don't really allow you to even reclaim the sand without some specialized equipment.
Building a sand castle with wet sand is somewhat analogous to the way green sand works, in that the sand is sticking to itself, so the castle stays together. It isn't particularly strong, and any of the edges are easy to break as are small features. Green sand is still fragile, but way easier to get better control. The graininess of my castings is mostly due to me not working very hard to find a source for finer mesh sand, which would help with detail in the castings. The molds are usually strong enough to withstand careful handling. Molten aluminum flows nicely through, and introducing it into the mold won't usually disturb the sand.
Packing the sand in the flask is called ramming, and it is the part that takes practice to master. What's nice about using green sand is that if you don't like your mold, you just re-do it, and you're not out any binder or sand. Other binder systems don't really allow you to even reclaim the sand without some specialized equipment.
Building a sand castle with wet sand is somewhat analogous to the way green sand works, in that the sand is sticking to itself, so the castle stays together. It isn't particularly strong, and any of the edges are easy to break as are small features. Green sand is still fragile, but way easier to get better control. The graininess of my castings is mostly due to me not working very hard to find a source for finer mesh sand, which would help with detail in the castings. The molds are usually strong enough to withstand careful handling. Molten aluminum flows nicely through, and introducing it into the mold won't usually disturb the sand.
