[Sca-cooks] Charcoal forge suggestion ;-)

[Jeff Gedney]

Never pour really hot metals into a cold mold... 

When possible, especially when doing finicky work like investment casting, preheat the mold. 

Here's a investment casting trick I learned a long time ago... 
using fine liquid clay, about the consistency of pankcake batter, dip the wax form several times allowing it to only partially dry between dippings until the coating is an even 1/8 inch thick, then air dry it as normal...
Then place the mold on paper towels on a ceramic plate, sprues down, and put it in the microwave on low for 10 mins, remove the towels, microwave on low for an hour, then on high for 15 mins. 
(dont do this if you are using metal at all in the form or mold, this is for purley Wax forms)

Then place the mold on the fire and let it slowly come to temp BEFORE you add blast air. Then and only then put in the crucible, in the same fire, and add blast air to melt, then pour, then cool slowly.  
If you make every effort to drive off moisture before pouring you will get far fewer spectacular accidents. 
When pouring very hot metals (600 degrees F and above) go SLOW and take each step carefully. 

Capt Elias

--------------------------------------------------------------
If you want to build a ship, don't drum up the men to gather 
wood, divide the work, and give orders.  Instead, teach them
to yearn for the vast and endless sea. 
  - Antoine de Saint Exupery 




---------- Original Message ----------------------------------
From: Stefan li Rous <StefanliRous at austin.rr.com>
Reply-To: Cooks within the SCA <sca-cooks at ansteorra.org>
Date:  Tue, 19 Oct 2004 00:47:31 -0500

>Phlip said:
>> Thank you, Brandu, for an excellent explanation. I was avoiding going
>> into
>> details, because this is SCA-Cooks List, nt EKMetalsmiths ;-) but,
>> since
>> he'd asked, was going to go into detail, and you saved me the trouble.
>Yes, thank you Brandu. Your explanation was very clear and did cause me 
>to go "oh yeah. I forgot about these not being glazed". I had been 
>mainly thinking of something that wouldn't burn up or melt or conduct 
>the heat to what I was trying to protect below.
>>
>> Stefan, the reason that modern high- temp ceramics are completely
>> glazed is
>> to prevent moisture from wandering into the clay. A flower pot, and,
>> for hat
>> matter, the unglazed clay cookpots like rommertopfs are designed to
>> soak up
>> water and release it slowly for the benefit of the contents. That's NOT
>> what
>> you want happening when you're using high temperatures with melting
>> metals.
>See folks, we are eventually getting back to cooking. :-) The lack of 
>glazing didn't occur to me. Firebricks aren't glazed.
>>
>> Stefan think- whattemperatures are the standard flower pots exposed
>> to? And
>> what temps are you getting to, to melt your pewter, whether modern
>> lead-free,
>> or old fasioned leaded?
>Around 500 to 700 degrees F.
>> And, what would happen if you poured a glass of water
>> onto your melted pewter?
>Not that much really. It tends to splatter but not explode. I've not 
>poured water into the molten pewter, nor do I wish to but I've started 
>pouring the leftover molten pewter into a pot of water which causes the 
>pewter to solidify into numerous small globs which is easier to handle 
>the next time around compared to the solid block that otherwise forms 
>in the bottom of my melting pot. I've even done this pouring the molten 
>pewter into a empty plastic soda bottle with the top cut off, filled 
>with water. The plastic will get warm and distort a little bit.
>>
>> Drakey, DON' try this to find out!!!!!!!!!!!!
>Considering it is you, Drakey, I agree totally with Phlip. Even with 
>just pewter.  *Especially* don't try this with molten brass. There is 
>at least one first hand account in my casting-msg file of someone 
>pouring brass into a mold that had gotten a bit of moisture inside. The 
>mold exploded throwing molten brass around the room and the 
>individuals. There were injuries. Among the problems of heating brass 
>to the point where it will melt, this is the reason I've not been in a 
>rush to try casting brass.
>
>Stefan
>--------
>THLord Stefan li Rous    Barony of Bryn Gwlad    Kingdom of Ansteorra
>    Mark S. Harris           Austin, Texas          
>StefanliRous at austin.rr.com
>**** See Stefan's Florilegium files at:  http://www.florilegium.org ****
>
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