Introduction: Bentonite Green Sand Recipe. Sticky, Oily and Just Great!

This is my new green sand mixture. This one consists of 87% of sand and 13% of bentonite clay. And some water of course :) I think in some way it's little better than my last green sand formula which consist brown clay. Bentonite clay is very sticky and oily. It's very different from brown clay. And this time green sand is really green! :)

Step 1: Bentonite Clay

Picture of Bentonite Clay

This particular bentonite clay was as hard as a rock! For this green sand recipe we need 13% of clay or in my case 2,2 kg (5 lbs).

Step 2: Adding Water

Picture of Adding Water

I couldn't effectively crash it, so I decided to add some water.

Step 3: Sand

Picture of Sand

The next stage is to add sand. We need 87% of sand. I used 15 kg (33 lbs).

Step 4: Mixing

Picture of Mixing

I couldn't mix clay and sand by hands, so I used a "heavy artillery".

Step 5: After Drying

Picture of After Drying

After a week of drying the result is grate. It works grate for casting.


kennaj (author)2017-08-10

I have the red clay for sand casting. Can I use this green clay in the same way?

DuralM (author)kennaj2017-08-10

Hi buddy. I'm sure it will work. :) The only question is the proportion. I would recommend to try from 13 to 30%. If 13% is enough than don't add more. Before bentonite clay I used brown clay:
It worked as well but I had to use 25-30% of clay and sand - the rest!

kennaj (author)DuralM2017-08-11

Thanks. First time anyone called me buddy.

DuralM (author)kennaj2017-08-11

You're welcome :) Good luck with green sand!

Gofish (author)2017-08-08

Thanks. Very easy to follow.

DuralM (author)Gofish2017-08-08

You're welcome Gofish! :)

Captain_Nemo (author)2017-08-08

At first I thought this was a recipie for home made cat litter... You might want to make something other than balls with it for the email thumbnail...

DuralM (author)Captain_Nemo2017-08-08

Hi Captain_Nemo! This is a mixture for making molds and after pouring metals. I didn't add more description because "green sand" is an expression connected to metallurgy, so... :) All my instructables are about metals melting and casting :) I have the other thumbnail and if you click on DuralM you'll see all my instructables and this one with other thumbnail (like for the video in the beginning). Website editors decide what to use as "email thumbnail". It's their decision. I appreciate that they add my instructable to this "email advertisement" no meter with which image! Everybody test green sand making balls from it. It's classic and works good. If you want to see how green sand works during casting, please read/watch my other instructables...

sharpstick (author)2017-08-08

I think cat litter is bentonite.

DuralM (author)sharpstick2017-08-08

Yes, but not always. Cat litter can be made of silica gel, wood or bentonite clay. :)

trukker (author)DuralM2017-08-08

Here in the UK our bentonite cat litter is sold as 'clumping' cat litter - i.e. it forms clumps when exposed to moisture. Makes the soiled clay easier to remove from the rest in the litter tray. I have used it in refractory mixes and in green sand - some people try to grind it but if you add enough water it turns to a slurry. Once dried, it can easily be powdered. But I agree, the fine powdered stuff is the best way to go.

DuralM (author)trukker2017-08-08

I used such "clumping" cat litter for my cat several years ago but that time I didn't have this hobby (melting and casting). When I started melting this "clumping" cat litter disappeared from the shops. Instead of it they started to sell cat litter made of small wooden pellets :) Several weeks ago I've this bentonite cat litter again but I have enough bentonite now :)

fuzzybeaver (author)2017-08-08

How many times have you reused it?

DuralM (author)fuzzybeaver2017-08-08

In fact just several millimeters near the metal burn. I throw away this black burnt layer. Some burnt green sand mix with good green sand but it's not a problem. It won't hold the shape as good as new but it's usually not a problem. :)

hmyers1 (author)2017-08-08

Commonly found at any pottery supply as well…price depends on quantity, 3$ 1lb lot—.65$ 50lbs

DuralM (author)hmyers12017-08-08

Thanks. :) That's useful information. It should be much more clean than mine.

hmyers1 (author)DuralM2017-08-08

May not be 'green' anymore :(

DuralM (author)hmyers12017-08-08


artswaff (author)2017-08-08

And after this the next step is to (what with the green clay?)

moonsoup (author)artswaff2017-08-08

You can make molds to cast many different shapes.

There are some examples in the related articles in the sidebar of this post.

Cast AWAY!

DuralM (author)moonsoup2017-08-08

That's true :)

DuralM (author)artswaff2017-08-08

I use it for green sand casting. If you're interested in metals melting and casting just click on my profile and you'll see a lot of instructables about that. :)

sgbotsford (author)2017-08-08

For others: You can buy bentonite as a powder from firms that make drilling mud. It's also used as a seal around the top end of wells. Go to any water well driller.

The Authors characterization of bentonite as sticky surprises me. My experience with it in it's natural formations in Alberta's badlands is that it is the most slippery mud imagineable. I found that standing on a 1% grade I helplessly slide to the bottom. May depend on water content.

DuralM (author)sgbotsford2017-08-08

Yeah, if wet it's as
slippery as ice :) When you mix it with sand it's very easy to make a mold. It
holds the shape excellent comparing to brown clay. So, as one of the readers
explained every grain of sand and clay sticks to each other. :) Nevertheless, I'll
arrive to Canada soon and check if Canadian bentonite clay is different from
ours :)

strayturk (author)sgbotsford2017-08-08

I think by sticky, he meant sticks to each other, not sticks to you :) Makes me think of sticky rice

DuralM (author)strayturk2017-08-08

You're right! :) Before bentonite clay I used brown clay (I don't know how it's called officially :)) and I had to use 25-30% of clay and 70-75% of sand. In the case of using bentonite clay 10-13% is enough, so yes it "sticks to each other" :)

DIY-Guy (author)2017-07-30

Looks "great." :)

DanP142 (author)DIY-Guy2017-08-08


DuralM (author)DIY-Guy2017-07-30

Thank you :)

ChrisH385 (author)2017-08-08

Bentonite is commonly used in wells due to its near cement quality (sealing around the well). THAT means you can get bentonite by finding someone that sells well drilling equipment. Bags are very cheap for pure bentonite. It beats finding bentonite cat litter and using that instead. Its usually powdered and very fine.

DuralM (author)ChrisH3852017-08-08

Thanks for the information :)

BeachsideHank (author)2017-07-27

That's a good find, a local source of free Bentonite, it'll work well for you, my home state is nothing but coquina rock, it being a penninsula. ☺

DuralM (author)BeachsideHank2017-07-27

Yeah :) Also, it's a lot of manganese ore here that's why we have an open pit and several mines. So, it's always possible to start melting manganese as well :)

If you do, make an instructable, I wanna see the process, never worked with manganese before :)

Ok! I also didn't do that :)

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