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Melting silver using kiln


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#1 High Bridge Pottery

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Posted 10 May 2013 - 10:04 AM

I have a friend who wants to make jewelry with silver and has been asking if it would be possible with the kiln we own. It has a top peephole which is a reasonable size.

So I have been doing a little research into the whole process and my idea is to build and fire a ceramic crucible that will fit in the top of the peephole. Then when I next do a bisque or glaze firing I could insert said crucible into the peephole to use the heat to melt the silver.

Silver melts at 900ish so either bisque or glaze would work as the lowest temperature I fire to is 1000 degrees centigrade.

I can see a lot of problems like things setting on fire, ruining the kiln and so on but would really like to help.
I was just wondering if anybody had attempted anything like this before?

#2 neilestrick

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Posted 10 May 2013 - 10:35 AM

No reason it shouldn't work. The only real issue is going to be getting the crucible in and out safely. Any reason you couldn't just fire it up, open the kiln and pull out the crucible, raku style? You could even have bisque work in there if the kiln will only be open for a few seconds.
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#3 Marcia Selsor

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Posted 10 May 2013 - 10:37 AM

I think that is not a practical approach. I taught a jewelry course when I first started teaching.
We melted silver with a torch in a crucible and then cast using a centrifugal caster.
I think you would not be doing a good even melt in a kiln...too slow. Even melting bronze in a furnace doesn't take more than an hour for 50 pounds or so.
Then what would you be casting with the melted silver?
One method I saw used which I stopped, was to take asbestos fiber , wet it in a jar lid and cover the molten metal. The steam forced the metal into the mold. That was in 1975 and asbestos was very common in studios.
The centrifugal caster is a healthier method of forcing the molten metal into a mold.
I think you need to consider what you need to do to cast metal before going much further. Melting a large quantity of silver would be very expensive for an experiment. I am assuming large quantity because small quantity is easy enough with a torch.

Marcia

#4 High Bridge Pottery

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Posted 10 May 2013 - 10:57 AM

I plan to design the crucible with some sort of curved handle on the top for easier removal. I could put it into the kiln but I thought this would be an easier option.

What happens if you melt the silver slowly? Does it just begin to oxidize quite a bit?
The reason we are not using a torch is just because we have no money and this is the only resource we have that gets 'hot'. I will have to read more about centrifugal casting, the idea of swinging hot silver round my head does not sound idealPosted Image

Planning to use the loss wax technique with plaster for the mould.


Thank you for the helpPosted Image

#5 trina

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Posted 10 May 2013 - 02:34 PM

Why not use silver clay?

T

#6 Marcia Selsor

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Posted 10 May 2013 - 03:02 PM

Trina,
That is a great idea!
Marcia

#7 Marcia Selsor

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Posted 10 May 2013 - 03:07 PM

I plan to design the crucible with some sort of curved handle on the top for easier removal. I could put it into the kiln but I thought this would be an easier option.

What happens if you melt the silver slowly? Does it just begin to oxidize quite a bit?
The reason we are not using a torch is just because we have no money and this is the only resource we have that gets 'hot'. I will have to read more about centrifugal casting, the idea of swinging hot silver round my head does not sound idealPosted Image

Planning to use the loss wax technique with plaster for the mould.


Thank you for the helpPosted Image

Plaster needs to be mixed with silica to become "lute" or investment plaster. Normal casting plaster will fracture from the heat. You need to do some major reading of casting, lost wax. BTW the carbon from the lost wax is bad for elements. We used a drum lined with fiber, with a hole in the bottom to capture some of the wax for bronze casting.
Trina's idea of precious metal casting sounds like the way to go in my opinion. When the silver fluxes you need to pour..like NOW. You probably would chill it if you are using gang molds.
Marcia



#8 Marcia Selsor

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Posted 11 May 2013 - 07:39 AM

a cheap way to cast jewelry is to use pewter and cuddlefish bone for the molds. Pewter melts closer to 500 F.

You can melt it in an iron ladle and melt it with a propane torch $12.
If you have no money , have you considered the price of silver?$50/oz.
Crucibles Graphite 3"=21.60 9" =$77
refractory ceramic crucibles about $5
Do you have a good recipe for making the crucible? One so the handle can manage being filled with heavy metal?
Investment plaster $31/50 pounds.

I have attached a link to casting supplies. http://www.contenti....ts/casting.html
The burnout ovens have the elements protected.

I see a problem when you have a studio for ceramics and converting it to another media..metal casting. Not necessarily compatible.

Marcia

#9 High Bridge Pottery

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Posted 13 May 2013 - 06:53 AM

Thanks for the great help Marcia, I would not be paying for any of the equipment and so on, just working the kiln. I will have to do some more research but I think this is not going to be possible with my skill level and resources. She seems to have the idea that it is relatively simple, I will have to tell her otherwise Posted Image Don't want to waste her money and end up with a broken pottery studio, this is what I can imagine happening.

Somebody was talking to us yesterday about this clay you can fire into silver Posted Image now that is something I have never heard of before. Think that is the route I will be taking! Sounds like there is a lot less that can go wrong.

#10 trina

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Posted 13 May 2013 - 09:20 AM

Thanks for the great help Marcia, I would not be paying for any of the equipment and so on, just working the kiln. I will have to do some more research but I think this is not going to be possible with my skill level and resources. She seems to have the idea that it is relatively simple, I will have to tell her otherwise Posted Image Don't want to waste her money and end up with a broken pottery studio, this is what I can imagine happening.

Somebody was talking to us yesterday about this clay you can fire into silver Posted Image now that is something I have never heard of before. Think that is the route I will be taking! Sounds like there is a lot less that can go wrong.


Just google silver clay. It is great stuff. You form it into whatever you want, fire it and the organic material that holds the silver particles together burns out, leaving your item. Same sort of principle like paper clay. T

#11 JBaymore

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Posted 13 May 2013 - 07:40 PM

It is called "precious metal clay" for a google search. Comes in both gold and silver.

best,

..............john
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#12 Boats

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Posted 18 May 2013 - 01:55 PM

I plan to design the crucible with some sort of curved handle on the top for easier removal. I could put it into the kiln but I thought this would be an easier option.

What happens if you melt the silver slowly? Does it just begin to oxidize quite a bit?
The reason we are not using a torch is just because we have no money and this is the only resource we have that gets 'hot'. I will have to read more about centrifugal casting, the idea of swinging hot silver round my head does not sound idealPosted Image

Planning to use the loss wax technique with plaster for the mould.


Thank you for the helpPosted Image


Listen to Marcia. She has a handle on this subject.

Simple plaster, should it hold up to the experience, will not likely provide agood result. Plasters are designed just for this purpose, such as Satin Cast20. To effectively utilize the lost wax process, the (wax) burnout alonerequires the mold to be heated and held at somewhere near 2000F to insure aclean good, clean mold. In the end, the only two ways you are going to get aclean casting is either via vacuum casting or centrifugal casting, with centrifugalproviding the best results.

Working with molten metal is loaded with pitfalls. Consider the idea of how you’regoing to clean out your kiln once splattered silver and flux. Oh yes, nearlyforgot, you cannot simply put silver and a crucible and melt it. It must befluxed creating many additional negative issues.

I am reading this forum because I don't know much about potting; however, I do know a little about casting gold and silver.

I guess the simple answer is "don't go there".



#13 Marcia Selsor

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Posted 21 May 2013 - 08:10 AM

Thanks Boats. I really wanted to say that "don't go there" but I thought some explanation might help to expand that realization.
I don't recognize your name, so welcome to the forum.


Marcia

#14 perkolator

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Posted 21 May 2013 - 02:25 PM

my grandfather was a dental tech and made silver crowns for teeth all the time. he also used the same method for making gold and silver jewelry for the family. his studio was in the garage, so i got to see the process on a regular basis growing up.

he used a spring-loaded centrifugal casting machine. The hard part is making the positive out of wax and casting a shell for it out of plaster of paris. The basics of the process are crank the casting machine to preload the spring and apply the stop pin, Insert "mold" into one end of casting machine, insert prepped silver into the opposite end/crucible. Melt silver with a $20 propane torch, pull the pin and let 'er rip. Couple minutes later the plaster is ready to break open and pull out your silver positive for cleanup work. Pretty sure you can buy a centrifugal casting machine for less than $150 - dunno if i'd risk my kiln for doing this. Just having to replace the elements after opening up the kiln at red heat a few times, or fixing a mishap would cost more than the centrifuge.

Good luck!

#15 Marcia Selsor

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Posted 21 May 2013 - 02:50 PM

Dear Perk,
Are you positive he used plaster of paris and not investment plaster?

Marcia

#16 neilestrick

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Posted 21 May 2013 - 08:05 PM

It is called "precious metal clay" for a google search. Comes in both gold and silver.

best,

..............john


PMC is one brand. Art Clay Silver is another. I have a good friend who is an Art Clay Silver instructor, and she says with small pieces, like quarter($) size or smaller, you can fire them with a torch, or even over a stove flame. Neither brand is cheap, though.
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#17 perkolator

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Posted 22 May 2013 - 01:15 PM

Dear Perk,
Are you positive he used plaster of paris and not investment plaster?

Marcia


I'm not 100% positive since he always had it in a tilt-bin in his lab, not in the original container -- but once I saw him refill and the bag definitely said plaster of paris on the label. Whether or not it had a secondary labeling designating it as investment plaster I cannot say. This was like 20yrs ago and the red label that's on Plaster of Paris was definitely different than today's markings. IIRC, he did pre-heat the plaster mold slightly before casting. Unfortunately He's no longer with us, otherwise I'd just call him up and ask.

#18 High Bridge Pottery

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Posted 26 May 2013 - 07:29 AM

Thanks Boats. I really wanted to say that "don't go there" but I thought some explanation might help to expand that realization.
I don't recognize your name, so welcome to the forum.


Marcia


You should just tell it too me straight Posted Image I can handle it. Still nice to know how complicated it can be and then make an educated decision.

The more you know....




#19 Marcia Selsor

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Posted 26 May 2013 - 03:32 PM

well. my advice then is don't go there. Try some precious metal clay...that would work in your kiln.



Marcia




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