To makegreen sand or like it also called molding sand (foundry sand) we need 3 ingredients: sand, clay and water.
Step 1: Digging Clay
Buy or dig some clay. I couldn’t find any clay (except fire clay) in the nearby shop and even in the big supermarket. Clay is a thing, which is not use during building, and redecoration works now. Of course, I mean that it's not used in a pure condition though it's 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.
If clay and sand are wet, you should dry them on the sun or any other accessible way.
Step 2: Find Some Sand
Buy or dig sand. I bought sand because it was far enough to the nearest reservoir and river where it’s possible to take sand.
Step 3: Make Clay Into Fine
Make clay into fine and clean the sand if it has any contaminant.
Step 4: Formula
My formula of green sand is 70% of sand and 30 % 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.
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.