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.

Step 5:

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.

<p>Another source for pure bentonite clay is a well drilling company. Ask is you can buy a bag of &quot;driller's mud.&quot; It comes in a finely powdered form and is great for use in making green sand. A 30-pound bag will last a long time.</p>
<p>Thanks for your good advice <a href="https://www.instructables.com/member/ChiGuy14" style="">ChiGuy14</a>. I can say that now I totally satisfied how my green sand works. I used it many times, so it's not bad. Also, I've got some bentonite clay from open-cast mine near my town. I will test it to find out if there is some difference. You can also see how this green sand formula works in my other casting instructables and youtube videos. </p>
I always wondered how green clay was made!<br><br>Just so you know, pure clay kitty litter is bentonite (see step 1). I found that out while reading up on cobb ovens.
<p>Yes. I see that a lot of people use cat litter as bainder. The only problem that cat litter may consist of different ingredients. For example, I didn't see cat litter which is a good binder in my country. I usually buy for my cat, some cat litter which looks like wooden pillets! Before I bought cat litter which consisted of silica gel. I assume that I can find some other sorts of such things through the Internet or in big supermarkets but it's easier to dig some brown clay :) </p>
<p>I'm with you, it's nearly impossible to find cat litter without added scents or &quot;odor absorbing&quot; crystals, unless you purchase online. In which case you might as well order powdered bentonite clay. However, I ended up grinding some that had the odor absorbing crystals and just filtering out the crystals through a screen. I used maybe 8-12 cups of cat litter and had more than enough clay for about 2-3 gallons of greensand that works perfectly.</p>
<p>That's grate that you have found the solution. At first I thought that I could buy some clay in shops which sold building materials. I was suprised to find out that nobody sold pure clay. :) Does your green sand allows to use it many times. I mean there is nothing left which can just burn during casting?</p>
<p>It's holding up so far. There doesn't appear to be any residue from stuff burning. I just crumble up the mold, mix it back into my supply, and add a bit more water if it's too dry.</p>
<p>That's good. I do the same. Just throw away very thin layer of green sand which contacted with melted metal. This sand is black, so I think it becomes bad binder. </p>
<p>Surprisingly little Bentonite clay gives very good results as far as cohesion goes, but if your home- brew formula works well enough for your needs, then it is a success too!</p>
<p>Yes. It works good. As far as I know when we use bentonite clay, than 13-15% is enough. But with brown clay 15% doesn't work. So, I took twice more and it started to maintain a form. I also got some bentonite clay, so will try it in the future. I'd like to understand if I could notice some differences. </p>

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