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AÂ Bramblebush Workroom Project
Foundry Work & Casting
A compendium of miscellaneous information
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Jan. 5, 1999 -  I just got a catalog from Johnson Atelier in NJ. They sell a self-contained "slurry room in a box" for making ceramic shells with 5 gals. first coat slurry, 10 gals. back-up slurry, 5 gals. pre-wet, 3 grades of stucco for $576.00. How does that compare to prices others are paying?
They also offer a condensed suspension kit that says it will keep slurry suspended for up to 60 days with little mixing. Something like this would help part-timers like me get a taste of ceramic shell casting and reduce the need for constant mixing.
Glen Carliss
Jan. 6, 1999 - This is not such a good deal. There are many ways to do the shell process. So this might be OK if you want to experiment. Here is what I do and use.
First, you really only need one slurry tank. I have used different systems but now I use Customcoat from Ransom and Randolf. This is not really a primer slurry but if you work it right it gives excellent results. So that eliminates the primer slurry in your kit.
Next you can use R&R "Corehardner" or just straight old coloidal silica as a prewet solution. This is used between the first couple of coats for facecoat strength and good bonding between these critical coats. This step is especially important with Customcoat since there is a plastic additive in it to speed drying buy inhibiting absorption from layer to layer. Only two grades of stucco are needed I'm not sure what the 3rd one is here.
You would have to buy a 200 grade flour for the slurry, an 80-100 for first coat and 30-50 for build coats. Plus, unfortunately, a 50 gallon drum of coloidal silica. I would go with a 100% silica system. I think John uses zircon, but I think silica is more forgiving and stronger.
So lets add itup Customcoat is around $400 for 50 gallons. Silica is around $15 a 55 lb. bag. You will need about 2 bags of flour 10 gallons of silica for a slurry mixture. One bag of face coat grade goes a LONG way. Maybe 4 or 5 bags 30-50 will cover this much slurry.
Now for the good news. You do not have to continually mix a slurry, especially Customcoat which is a thinner slurry than most. We have left it unmixed for 4 months with no problems. Actually this is how I found out mixing was not necessary.
We had a fire and were down for 4 months and without power. I thought the slurry was a lost cause but I tried to bring it back just for the heck of it. No problems. If you go this route, I can advise you on this procedure.
You do need a 24-7 mix during shell building though. This is a simple enough setup. You really only need to min. 2 min. in every 10. An inexpensive timer is used for this.
Do the math up above and you decide. Â I do not like the additive idea. I'm sure they do not use it.
Mark Parmenter
Jan. 6, 1999 - Â >Wanting to pour copper and aluminum ingots and sand castings. I have an old >kiln made of lightweight firbrick and will use propane as my gas with >compressed air for added pressure. The max temp I need is 2000 degree's >copper melts at 1980
jeff
Why use "expensive" compressed air? Just put a small blower on the burner. My burnout kiln actuqally has just a small hair drier stuffed into the end of te pipe. The melting furnace has a small squirrel cage fan (1/20hp) bolted on to the end with a controlling "flap" over the air intake so air flow can be regulated as needed. Also, I like the bronze up to 2100 to 2200 F depending on the piece but the propane will get you there just fine.
John Dach
Jan. 6, 1999 - Thanks for the good advice backed up with the dollars and cents figures I did not have on ceramic shell consumable supplies. In a stroke of excellent timing, I got a call from Bob Pawlak of Remet today. He monitors this list and saw my name in recent foundry postings. He called to follow up on a discussion we had a month or so ago. He speaks highly of both you and John Dach. After talking with him I am a step closer to taking the plunge.
The last item that is fuzzy for me is what people are using for shell firing kilns. I can do the initial melting and recapturing of the wax as John described in a recent posting. But what exactly are people using as a kiln to fire the shells. Are they commercially available or are most people using kilns they have built themselves? My melting furnace has a capacity of about 30 lbs. of bronze so that will do a lot to determine how big my shells and kiln need to be.
I have read what Young and Fennel said about this subject. They suggest 2 books - Kilns: Design, Construction, and Operation by Daniel Rhodes and Kiln Building with Space-Age Material by Frank Colson. I will check them out but I have a feeling they are not available at the local library. So I would appreciate anybody's input on the subject.
Glen Carliss
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