Hi B.J. and thanks for replying,

Since I am completely unfamiliar with this process and the properties of ceramic, I wasn't aware that chipping out the casting would be necessary. My primary goal is to attempt to create a mold with the metal filled crucibe attached to the bottom, once heated to casting temperature, I would like to turn the whole unit right-side-up to facilitate the cast. This is an ancient method of bronze casting and I wanted to give it a try with modern mold making materials. From the scant information I was able to gather from a book, the method is faster than investment casting, but unfortunately calls for the use of cow or horse dung LOL...

The ingrediants include a mixture of crushed charcoal powder and potter's clay moistened with water as the first coating that goes over the wax. After that is dry, a mixture of 40% charcoal powder, 25% manure, 25% potter's clay and 10% refractory clay is built up over the piece to form the outer portion of the mold. Unfortunately the source I gathered this from says nothing about "how" the mold is removed once the casting is done, but my primary interest is in finding a modern material that can take the place of manure in this process. Any suggestions?

I watched demo several years ago at the Yuma Symposium on Ashanti casting and I believe that is the process you are talking about. It was not teribly complicated and there was some failure risk and not something you would want to do for production work. I do not recall what the exact formula they used for the investment and suspect there may be an internet discussion on the process. I believe the SNAG journal had a write-up on it.

Fred Zweig
Metalsmith

Replace the cow manure with perlite..available from most garden centers. Send us lots of pictures...also do a web search on a material called hypertufa..peat moss could also replace the dung...thinking about this some more I would use either regular investment as a slurry base coat or plaster of paris.about 1/4 inch thick then cover that with your mixture...Vent.. Brad

The book "Goldsmithing and Silver Work " by Charles Codina
under Under jewelry vessels and ornament has a nice mention of this casting technique..I'd use per-lite or vermiculite..both are minerals you are looking to replace a binder...I would want a binder and some more refractory..make sure this is bone dry before heating..bring up to temp very slowly...Not even close to ceramic shell casting..by todays technique. This is not faster than investment casting,,it is going to take days for your mold to get bone dry..I'm ready to go in a couple of hours..Brad

Thanks for th e material suggestions, and yes B.J., that is the book ;-)

...Days to dry eh? Codina didn't mention that in the book :-( Infact from the lighting in the photo, it looked as if everything had been completed the same day. Could I not dry the layers with an hour in the kiln for each? Or even with a heating gun?

And if I do proceed with the experiment, I promise to post pictures.

BD
My ceramics experience tells me bone dry is the condition you want a clay body to be in before it is bisque fired..Personal experience if they are not bone dry they crack or can explode. Bad On the other hand as a kid I dug some clay from a creek made it into a spear point stuck it on a stick and heated it in a camp fire.. Got quite hard and didn't crack or explode..I'm inclined to say try the heat gun approach..Steam and hot gases are castings biggest problem area. This investment may be so very porous that the steam and gases escape through it. Bring up to temp slowly. Expect steam and smoke..I think I'd try it. FWIW Brad outside only Test fire some of the material without wax to see what it does.

BD
I've been thinking about this a little more. Intrigued by this method. While your at the garden center looking for per lite, vermiculite or peat moss. In the same isle right beside them are bags of sanitised "cow manure". Gardeners refer to the material as an organic soil conditioner, guess when you think of it that way people will happily put it in the back seat of their BMW. Can't explain it hmmm. So have the right side of your brain give the left side some money. Then head off to the garden center..You may just find everything you need in isle seven. Clay = kitty liter maybe
Cow manure = organic soil conditioner. The African metalsmith gathered his materials crank up the Hummer and get to gathering materials..Modern man..While you are at the garden center check out those porous looking not really
concrete looking planters...They are made of hypertuffa..check out the archive section of this site for more info on primitive casting methods..
but most of all get over it, get on with it, I expect pictures this week...While you're having all this fun you might want to check out making a flower pot charcoal foundry, give us time and we'll turn your back yard into someplace wonderful.. enjoy go for it. Brad

BD
I forgot the standard AM reply...WEAR GLOVES..Get a cart at the garden center..Leave the cell phone in the Hummer. Nothing messes up a good forage for materials faster than a cell phone..Pick up a bag of charcoal and some yak burger on your way home..While the left side of your modern brain makes supper the right side can be making ash...use plenty of charcoal..don't burn the burgers. Waiting for pics Brad

k

If you have a digital kiln, clay will accept heats of up to 180F for the first two hours and then can be boosted to about 300F for the next two hours. For the final drying time (and hope that you don't develop cracks here) you boost it to 550F for the last two hours.
Make sure that the clay is dry in appearance before putting it in. If you try 'steaming' it dry you will just crack up and ruin a lot of clay.
One thing that I tried was firing a thin china coating around my wax master and then coated it with silicon casting material before it dried and then fired it quickly at 1200F for about 1 hour. I had a nice china mold that took the metal quit nicely and then shattered off the final product but was easily repeated. The problem is mess, cost of materials and handling such a delicate mold without shattering it as you eith vacuum or pour the metals in. And believe me you have to pour fast while it is hot or the metal just stops flowing in the darnedest places.
I like the other suggestions on this board. I am more of a traditionalist and don't mind going out to the farm and getting the dung as it is the best material for polishing the final piece that you can get. You can't buy a finer material!

vowie