Thread: Sand casting

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So this thread started out as a response to one of UnOrthodox's threads. I'm beginning to work on one of my projects for this up coming Halloween, and I needed a lot of skulls that look like they're made of stone, so I went looking on casting and forging websites and came across sand casting. What they describe there is making something called green sand. The long and short of home made green sand is go to you local home depot and buy a bag of play sand, sift it through window screen and set aside the fine sifted sand, then buy a bag of self clumping cat litter(this is made of Bentonite), and pulverize it, I used an old blender and ran it till it was a fine powder, combine 30% powdered cat litter and 70% sand. Add water a little at a time and mix thoroughly until the mixture holds together when you squeeze it in your hand. This mix will give you a very smooth clean casting, in other words not what I needed for stone skulls, so I started over, this time omitting the cat litter, and just moistened the sifted sand, this worked great, as you can see below. I use Great Stuff spray foam. This method can be used for casting just about anything you can think of from skulls to small architectural pieces, to really big architectural pieces, to Tombstones. Have fun with it!


I started with a cheap foam skull and cut the face off of it ( I have both with and without the jaw-bone)




I use play sand from Home Depot for the mold:



next I press it firmly into the sand carefully packing the sand all around the foam skull



and remove it from the sand



Add foam and let dry:



It comes out looking like a skull carved in sandstone





That's the long and short of it.

That looks great! I DO need a clean casting so how do I grind the kitty litter without ruining my only blender? Also....once you get the green mix wet and make a mold does the kitty litter in it harden(clump) and keep the shape you created or can it be reused for a different mold?

Well you could make a tumbler out of a five gallon bucket, a motor and some rollers and put some stones in with the cat litter, that should work, would just take a bit longer. Also, no it doesn't harden unless you let it get really dry, I keep mine in a plastic bag and reuse it over and over again, you just need to keep it moist. If you need to make a really smooth casting, just change your ratio of sand to cat litter, the more bentonite you have in the mix, the smoother the end result. Also the finer you can sift the sand the better your end casting will be. I was looking for a rough stone look, so I didn't sift the sand really fine, if you want a smooth finish I would suggest doubling up your screen for a finer mix.

Not sure if this will help or not, but if you need a smooth bentonite ( I assume cat litter is coarse) find a well drilling supply company or a water well driller and ask for drilling mud.......bentonite (which is a clay) comes in 50 pound bags and has the consistancy of flour. It is used in well drilling fluid to make a smooth wall on the bore hole so it dosen't cave and to help move cuttings from the hole. It is relatively cheap.....(around 7 dollars for a 50 pound bag.
I never thought of using bentonite and sand for casting.......Thats a GREAT idea Thanks for posting the idea!

Incredibly easy and looks perfect for tombstone details. Thanks so much for this!

Originally Posted by riverswampboat

Not sure if this will help or not, but if you need a smooth bentonite ( I assume cat litter is coarse) find a well drilling supply company or a water well driller and ask for drilling mud.......bentonite (which is a clay) comes in 50 pound bags and has the consistancy of flour. It is used in well drilling fluid to make a smooth wall on the bore hole so it dosen't cave and to help move cuttings from the hole. It is relatively cheap.....(around 7 dollars for a 50 pound bag.
I never thought of using bentonite and sand for casting.......Thats a GREAT idea Thanks for posting the idea!

I didn't know anything about well drilling, so didn't know about getting bentonite that way, yes cat litter is course, but relatively easy to make fine, just be sure to use a mask so you don't breathe the dust as it is very bad for you (black-lung). Believe it or not, but I almost didn't post this, as I mostly lurk now and don't do much in the way of posting anymore. I really wasn't sure anyone would be interested in this at all.

Oh you're welcome Terra, I should mention that if anyone is going to make a two part sand mold, you should sprinkle the first half of the mold with talc before putting more sand in to make the second half, that way you can separate the mold cleanly.

I been doing this for years but I only use sand with water, just enough to dampen the sand so it holds together when you press the object you are casting into the sand.

The major problem when casting with greatstuff is shrinkage and I had mixed results with that...sometimes it does and other times it doesn't.

You won't get perfect casting but it's a easy way to get castings for pennies when you don't need perfect. Here's a few that I did using sand...

I used a foam head, a plaster skull and a biglot skeleton to make these sand cast then



used my own hand for these



used another foam head and my own hands and forearms for these....before the foam is fully cured (but not sticky) you can form it by pressing on it to get smaller arms



add a little caulk and spray paint to get that skinned zombie look...total of 15 minutes of work time from casting to finish and maybe $3 dollars/one can


here's another sand cast head with the foam head I used as a model

So how do you get both sides, like this the hands and arms? Is there still a flat edge you can't see in the pictures?

Raid thrift stores and look for a cheap mini-food processor or coffee grinder. It'll take longer, so depending on the amount you need you may as well buy a cheap blender or food processor instead. I recommend you gently "pulse" things until they're small, then full power chop the rest of the way. It was a freak accident, but back when I was active in the polymer clay newsgroups, someone using a food processor to condition (knead) the clay had a blade snap and fly right through the (plastic) tub into the wall.

Edit: the main issue is do not do anything that could cause the blade to "jam" while spinning. A cheap food processor is actually more likely to simply burn out the motor or strip the gears, an expensive one will power right through it until the blade breaks.

http://groups.google.com/group/rec.c...6a31adac?hl=en

Originally Posted by chinclub

So how do you get both sides, like this the hands and arms? Is there still a flat edge you can't see in the pictures?

Here's a video that shows the green sand method for making a two part mold, that's the sand with the clay in it.

http://www.youtube.com/watch?v=SVUSJuYQhA4