Pouring Pure 999 Silver ISSUES

[SilverWood]

Hi All, thanks for any help in advance....

I own a TableTop Eletric furnace. I am setting it to 2000ﾟF and melting my set amount of fine silver. I have tried both a 100% graphite crucible and a graphite/ clay crucible.

I am pouring into open mold of patterns in petrobond clay.

The silver is melting beautifully and is liquid for sure. I get a nice smooth pour and it looks great /smooth and convex. But only for a second as the silver then sort of bubbles up around the top open edges. It also gets a concave impression.

The design is coming out nicely. It is just the open back of the piece.

I of course am looking for a nice smooth back.

I tried to upload pictures. I am not using any flux, so not sure if that is needed or lower temps. I am lost.

 

[niks neims]

It is gasses escaping molten silver as it cools - mostly oxygen (molten silver absorbs it from the air) , it is all theory for me, but if you search around a bit you will find it discussed at lenght here.... Many solutions have been offered, including melting and pouring under yellow flame (reducing athmosphere).... I don't know is that viable in your situation since you are using electric furnace... Maybe you should use some kind of flux.. Try the search button, all I know for shure is that this question has been discussed here before and best possible answer already found

And welcome to the forum!

 

[SilverWood]

Thanks, I did try searching, but my keywords were not working, lol. You have given me more info to search. Thank you!

 

[niks neims]

No problem, glad to help, I hope you find your answer. If you have Hokes book (you should ), I remember it is mentioned there also!

 

[SilverWood]

Ok, so I spent days readinig everything i could about this problem.  Everything I am finding is regarding melting silver with a torch and an oxygen depleated flame.

I am unable to find a solution for melting and pouring from an electric furnace.

Has anybody else run into this and found a solution?

 

[snoman701]

An electric furnace should not create a problem. If anything you can add some charcoal to borax to ensure the silver never sees an oxygen environment.

It's likely the petrobond clay.

Try investment that is properly fired, or a heated cast iron mold.


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[snoman701]

When I've used petrobond before it was for aluminum casting, which is considerably lower temp.

I thought petrobond was no longer available?


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[Ravn]

Many things has an influence on the cast result.

http://www.lbma.org.uk/assets/blog/alchemist_articles/Alch47Stokes.pdf

 

[Lino1406]

The problem here is not using a flux. In this case, for heat balancing and
functioning as a riser, what is correct for any metal

 

[goldsilverpro]

The first thing I would try is lowering the temp. to about 1800F or 1850F, at most.