Clay

Clay · 09-17-2009, 09:03 AM

This is somewhat on topic as my use is for a mini forge, that is basically a cast iron frying pan full of clay. It makes a good insulator for being able to heat metal wth a torch and not burn anything. Anyway, I had read about this by Googling and finding plans for various forges.

A common tip I ran into was that an easy to find source of pure clay is clumping cat litter. I wanted to share my experience with using that.

I bought a 14# jug of all natural unscented clumping litter. It listed one ingredient - clay. It was a brand I had never heard of (most of the name brands have scents and additives) and is on sale at Harris Teeter for $3.50 with a VIC card. It's dry, so when you add water it almost doubles in weight and volume (the latter point surprised me). So it makes about 25# of clay, I guess. I only made enough for my use and have a lot more left. I was going to mix it with our regular scented litter for the cats, but after my experience with it, I am keeping it for future use as clay.

The hardest part about dealing with it is getting over the mental block of it being cat litter. I started out wanting to stir it with implements (too stiff for that) and then with gloves (kind of works but hard to keep them on). I gave in and used my hands and it was simple. This stuff is not an excuse for clay, it is clay - 100% pure gray clay, the type you could use for pottery or sculpting as well as making fireproof insulation.

Anyway, just pour some dry litter into a large container and start adding water. I don't have any exact numbers to give you; it depends on how pliable you want it and I suspect that different brands will be at different MC to start with, but I think I ended up adding almost as much water as I had litter, so I might start with 2 parts litter to 1 part water and then add water as needed while mixing. The grains disappear and it melds into one mass almost immediately but you have to keep kneading it as it will have pockets of dry grains.

Once it is reconstituted, treat it like modeling clay. You can wrap it tightly in plastic wrap to save it, leave it out to dry slowly or fire/bake it to dry quickly (I am not an expert on that; I know it can be done wrong, so seek further instruction). If someone has tips about drying properly, please post a follow up.

Oh yeah, soap and water clean up. It's non toxic and inert.

EDIT - I want to stress that if you are going to use it for fireproof insultaion or fire it in a kiln, it is very important that you find the 100% natural stuff with no scents or additives. Who knows what that stuff might do when heated. Also "crystals" are bad in general; some are silica and the dust is unhealthy. Just get 100% clay; it is not hard to find. There is also 100% clay that is not clumping litter even cheaper. My understanding is that this is not bentonite (sp?) clay and will be more mud like and harder to work with. But that is second hand; I followed the advice to get the clumping stuff.

rbdoby · 09-17-2009, 10:16 AM

This is the 3rd good use for cat litter I've heard of.

1. I keep it at work to soak up spills on my concrete floor.
2. They used it to mark where to dig the footers when our house was built. Like chalking the lines on a ball field.

I had a little experience with clay in college. (Yeah, I was an art major) After it has air dried to what is called "leather hard" pottery is put in a kiln and fired to 1800°. I don't remember how long to maintain the 1800° heat but the cooling process took about 24 hrs. Make sure all the air bubble are out of the clay. During firing they will expand and cause cracks or even explode.

Rick Doby

Sealeveler · 09-17-2009, 10:20 AM

Thanks for the info.My daughters always had some project going on in school were they had to use modeling clay.Tony

CarvedTones · 09-17-2009, 10:55 AM

Originally Posted by Sealeveler

Thanks for the info.My daughters always had some project going on in school were they had to use modeling clay.Tony

That is one of the main reasons I decided to hang on to the rest of what I got. It is basically this stuff:
http://www.joann.com/joann/catalog.j...PRODID=prd2074
$8.50 for 5# of moist gray clay (and that is not a terrible price; the same brand is $12.50 at Target) and I got 14# of dry that will probably be 25# of moist for $3.50.

scsmith42 · 09-17-2009, 12:18 PM

Andy, that's good info - thanks for sharing.

I've been kicking around the idea of building an outdoor wood boiler (based upon the Fred Seton design) sometime this winter, and the clay kitty litter may make a good insulator for it, rather than the concrete that I was considering.

Scott

nelsone · 09-17-2009, 01:15 PM

From a carving perspective, that would be good for making maquettes! I imagine there some other ideas that can be developed too! Thanks for sharing!

MrAudio815 · 09-17-2009, 02:01 PM

Hum,

Very Interesting... I am sure when my Son is older he will have some fun with that clay and @ $3.50 for about 25lbs sounds real good. It may last him his whole life.

I am also interested in how you use it for insulation??? Can you use it on a home like under the crawl space in the cracks, or just on the underneath sid of the floorboards? Just thinking???

What's your thoughts?

CarvedTones · 09-17-2009, 02:18 PM

Matthew,

Fireproof insulation for very specific uses. I am making a "mini forge". I want to take small strips of tool steel and make knife blades. To do this, I have to anneal it by heating the whole strip to red hot and then letting it slowly cool. The it will be easy to bend, shape, drill, etc. Then later to harden it, you heat it and then dunk it in oil to cool it quickly. You can get it hot enough with a propane torch, but you have to have some way to hold it or a place to set it where you won't burn something while heating the blank. A cast iron pan full of clay will work to do that. I am not sure why the pan has to be cast iron if the clay really insulates well enough, but this doesn't seem like the sort of thing I should experiment with, so I got a cast iron pan.

Ed,

A couple of things to keep in mind...
It will not cure rock hard unless it is fired.
It will shrink some when it dries.

So if you want your models to be on an exact scale it probably isn't a good choice.

I may also try making a small batch with mineral oil instead of water. I read that is one way to make modeling clay that pretty much never hardens.