# Cast iron muffin pans as molds



## danny987 (Dec 1, 2010)

Has anyone used these as molds? I would be using it to pour copper. Thanks


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## Barren Realms 007 (Dec 1, 2010)

You will probably want to pre heat the mold so it does not crack from the sudden temperature change.


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## Anonymous (Dec 1, 2010)

Make sure you do not preheat it too much,or the gold will aglomate with the iron.500 deg. farenheit will be more than sufficient.


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## Barren Realms 007 (Dec 1, 2010)

mic said:


> Make sure you do not preheat it too much,or the gold will aglomate with the iron.500 deg. farenheit will be more than sufficient.



He is pouring copper..


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## Anonymous (Dec 1, 2010)

Better make it higher than 500 then,but careful because it will still aglomate.Do not preheat it high enough for it to glow.


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## goldsilverpro (Dec 1, 2010)

After pre-heating and before pouring, I would brush a thin coat of motor oil on it to act as a mold release for the copper. Or, put a layer of carbon on it with an acetylene torch.


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## danny987 (Dec 3, 2010)

So i noticed that the surface of the cast iron is no smooth. well this not be a problem?


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## Barren Realms 007 (Dec 4, 2010)

danny987 said:


> So i noticed that the surface of the cast iron is no smooth. well this not be a problem?



Will not matter a bit.


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## Harold_V (Dec 4, 2010)

danny987 said:


> So i noticed that the surface of the cast iron is no smooth. well this not be a problem?


Depends on a few things. I expect it is intended to function as a mold (although not for metals), so it should have proper draft. It should release fairly well, assuming there's no undercuts anywhere, or any divots that can allow the cooled copper to key to the mold. 

It stands to reason that the larger the surface area in contact, the more likely it would be to have one or more stick. If you use much force on cast iron, it will shatter, so beating on it is not an option. 

Unless you have a specific purpose in using thin cast iron for a mold, you may wish to reconsider. You can make a very functional pig mold by welding ends on a piece of angle iron that has been sawed such that the bottom of the V is the narrowest width, and the legs the widest. It would look like this from the side \______/. The pieces should be welded on the outside, where they'll serve as legs to hold the mold at the proper attitude. If you build one to this design, it will insure that you don't have any issues with the cast copper pieces releasing. 

As before, preheating the mold is important, as is applying a release, such as carbon black or a coating of oil. End plates should fit without creating any gaps that can allow the copper to key. 

Harold

Edit: shold you decide to build a mold such as I suggeted, the thicker the angle iron the better. Don't use thin material. Nothing less than ¼", and I highly recommend it be heavier. There's a lot of heat in molten copper that must be absorbed by the mold.


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## Barren Realms 007 (Dec 4, 2010)

I have about 400-500 lbs of lead made with a mold probably like the muffin pan and have done 150 lbs of aluminum or more with the same mold. Never used a mold release and never coated the mold. I have never had one stick and yes it has been beat aginst stuff to release the metals. I am not saying the same thing will happen with copper. I agree with Harold in the fact that the copper will be more prone to sticking to the mold than lead or aluminum. And there is more of a chance or damage to the mold because of a a few reasons.


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## Harold_V (Dec 4, 2010)

The big issue here is the temperature involved. Pouring temperature will be in excess of 2.000° F, which raises hell in ways you may not understand. The real risk is the rapid localized heating, which causes the cast iron to expand rapidly, even though it's been preheated. Cast iron responds to uneven heating very poorly. I expect that cracking will be a factor. There's more to it than that, too. For example, all one has to do to get the copper to solder to the iron is pour in one place. With the wall thickness of the mold on the light side, the excessive heat transfer, coupled with the scrubbing action of the molten stream of copper (from pouring) acts to scrub the surface clean enough to experience soldering. I had it happen with ductile iron molds with far greater mass, and that was pouring silver, which melts at a lower temperature. It should also be noted that silver is eager to solder to other metals, far more so than copper, so maybe that's not a fair test. Still, it's best to approach this from the perspective of being informed. Freeing a stuck ingot isn't one of the things I count as a pleasure. 

You likely understand that it's not easy to solder aluminum, so sticking, so long as there's no keying, isn't an issue. With lead, it's even less of an issue, considering the reduced temperature involved. Of course, I expect that one is pouring to surface that is well oxidized. All bets are off on a clean iron surface, where, with just a little bad luck, you can get lead to stick. There's little that beats a generous covering of lamp black where molds are concerned. It is available from foundry supplies ----for dressing molds. 

Harold


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## gmiller (Dec 25, 2010)

Hi all, 

I have used cast iron molds with great success over the years. I have a table top kiln and preheat my molds by placeing them on top of the kiln prior to turning thr kiln on. I set the temp. of the kiln to 2000 degrees F.

My mold was obtained from Wally World but can be found at many hardare or sporting goods stores.It was origionnally intended for pouring lead, but I ground the lettering in the bottom of the mold off with a Dremel type tool and ground the sides the same way to get a smoother bar. 

I use a graphite grease as a release coating, (available at any auto parts store). The first time I used the graphit grease I got some smoke from the grease, but the graphite remained and easily released the pour without any sticking. I have found that I don't need to re-grease the mold for up to 30 pours, and even then I only did it as a precaution, still not getting any release problems. I would think that this would work just as well with copper as both gold and copper have melting points in close proximity.

Hope that helps.

Gary


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## butcher (Dec 25, 2010)

Made a small mold from an old Iron pipe plug, it already had the mold shape cup. I drilled out the bottom to form a funnel shape in bottom being careful not to drill all the way through, and polished the inside, with torch sooting worked great for getting small beads from hot flux, and as mold for small dish pours. I welded it to a small piece of steel for a base plate.


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## Barren Realms 007 (Dec 25, 2010)

butcher said:


> Made a small mold from an old Iron pipe plug, it already had the mold shape cup. I drilled out the bottom to form a funnel shape in bottom being careful not to drill all the way through, and polished the inside, with torch sooting worked great for getting small beads from hot flux, and as mold for small dish pours. I welded it to a small piece of steel for a base plate.



How aout a picture of that set up.


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## butcher (Jan 2, 2011)

sorry I do not know how to get pictures on a computer and then onto forum.
I will see if I can find somebody to do that.


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