I started experimenting with small quantities measuring first 1KG of sifted and dry play sand. I used a mixer to grind the cat litter (clay) to a powder stage and then sifted 100gr (10% of clay), mixing both together and after just adding small amounts of water at a time. The process was very quick and the sand mix was ready after performing the squeeze test.
My first casting was an aluminum eagle. This was the 12th aluminum eagle I have casted and the result was very promising. No difference in the quality of the casting from the oil bonded eagle castings.
I decided to cast a bigger aluminum object this time so I casted my 3rd aluminum sun. The quality of the casting in this case was not the same. The oil bonded sand sun casting was with almost zero defects and the green sand casting was with a lot of defects mostly porosity. Perhaps from not ramming the play sand hard enough or from the lack of vent hole but again it's not the worst sand casting. I hung the sun on a garden wall and the defects aren't even noticeable it just needs a bit of sanding and polishing.
How oil bonded sand VS green sand:
Oil bonded sand produces a better quality casting but is much more expensive then green sand. Green sand is cheap, easy to make and re-usable. Oil bonded sand is stinky, smokey and stains everything it comes in contact with. Green sand is clean with no smell. Oil bonded sand is much more sticky then green sand. Green sand is alot more fragile then oil bonded sand.
If you are looking for amazing finishing on your casting use oil bonded sand. If you want a cheap solution for casting, for example some heavy machinery parts green sand will do just fine.
Here is a 5 min' demo video I made of how to make casting green sand.
