Green sand formula - how to make molding sand
To make green sand or like it also called molding sand (foundry sand) we need:
1. Buy or dig some clay. I couldn’t find any clay (except fire clay) in the nearby shop and even in the big supermarket. Fire clay is a thing, which is not use during building, and redecoration works now. Of course I mean that it doesn’t use in pure condition though its still important ingredient in many building materials.
I had to dig some clay in the cellar. This cellar was built half a century ago so the floor made of clay. I should also mention that this is brown clay. I’ve heard that it’s recommended to use green (bentonite clay) but I didn’t have it, so used what I had.
2. Buy or dig sand. I bought it because was far enough to the nearest reservoir and river where it’s possible to take sand.
3. If clay and sand are wet you should dry them on the sun or any other accessible way.
4. Make powder/fine of clay and clean the sand if it has any contaminant.
5. My formula of green sand is 77% of sand and 23 % of clay. At first, I tried to use 15% of clay but it didn’t work well. I assume that with green bentonite clay even 15% could be fine but not brown clay.
6. Finally mix sand with clay. During the process, spray some water. You will see that it’s enough when your mixture is able to maintain a form.
That’s all. This green sand formula is working. It is possible to use this molding sand again and again.