# Interesting video on constructing an electric furnace



## Auful (Feb 3, 2013)

I have read about the pitfalls of electric furnaces, how acids will destroy the heating elements. However, I found this video quite interesting nonetheless. Perhaps others have already seen it, but I though I'd share anyway. http://www.youtube.com/watch?v=en4yhzLuD9A


Edit: corrected spelling error in title


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## butcher (Feb 3, 2013)

Auful,
I just wish he would have added a few more details, like what size rod he wound the nichrome resistance heater wire on, how long the spring was once he stretched it out, what the cold resistance of the 70' of 18 AWG nichrome wire was, and what actual current and wattage would be when run on 240 VAC, I was not impressed by his connections of element to wire (for safety, and durability reasons) these should be mounted rigidly to fixed insulator material.

Although most of these questions of mine can be easily figured out by a little more research of data on the wire used.

All in all it is a nice furnace design and very informative video on how he built it.

P.S.
I guess one place to look for some of those answer would be the web site of the company who made the video.
http://www.tempco.com/Catalog/Section%2015-pdf/Sect15-Resist%20Wire.pdf
http://www.tempco.com/Accessories/CrmcBlcks_EnclsdTrm.htm
http://www.tempco.com/Default.htm

I am not promoting this company, and do not know if their prices are reasonable or not, but they do have some things that can help heat your solution on those cold winter nights, just reviewing the website may give you a few ideas to getting things warm.

Thanks for sharing.


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## Jimmy (Feb 3, 2013)

I buy a lot of stuff from Tempco. There prices are not very good but they do have good service.

I perfer Molybdenum Disilicide heating elements. They dont seem to have any problem with acids. But they do require a power supply.
They are also good to +3200F.


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## Drimacus (Feb 4, 2013)

The video shows an interesting design but there are drawbacks. Nichrome wire is ok for aluminum smelting but poorly suited for the higher temperatures required for silver and gold. Also, all the element above the crucible and perhaps below could be exposed to corrosive gases or vapours that will shorten the life of the heating element. The prices of element wire listed on the linked website are very expensive, a popular pottery house in Ontario offers similar heating wire for about one-third the price.


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## samuel-a (Feb 5, 2013)

Drimacus said:


> but poorly suited for the higher temperatures required for silver and gold.



Quite a statement... What do you suggest instead ?

I have been working some NiCr heating elements to 1250+ C without any problems...


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## Geo (Feb 5, 2013)

samuel-a said:


> Drimacus said:
> 
> 
> > but poorly suited for the higher temperatures required for silver and gold.
> ...




hey Sam. i just noticed the link in your signature line, http://rapidshare.com/files/1770165842/GNS_-_e-Scrap_Yield_List_v1.0.pdf

the link doesnt work.is it suppose to be up yet? it say access denied by up-loader.


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## samuel-a (Feb 6, 2013)

Geo said:


> samuel-a said:
> 
> 
> > Drimacus said:
> ...



So that why no one is downloading it.... sorry. ^__^
i'll try tofix it later today.


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## samuel-a (Feb 6, 2013)

Geo said:


> hey Sam. i just noticed the link in your signature line, http://rapidshare.com/files/1770165842/GNS_-_e-Scrap_Yield_List_v1.0.pdf
> 
> the link doesnt work.is it suppose to be up yet? it say access denied by up-loader.




The link should work now...


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## FrugalRefiner (Feb 6, 2013)

The link worked fine for me. Very nice Sam. Thank you so much for sharing your hard won data with everyone!

Dave


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## Drimacus (Feb 6, 2013)

Direct from the Kanthal handbook. Kanthal A1 or APM wire has longer life than NiCr at high furnace temperatures.


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## Auful (Feb 7, 2013)

Drimacus said:


> Direct from the Kanthal handbook. Kanthal A1 or APM wire has longer life than NiCr at high furnace temperatures.



Thanks Drimacus!


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## samuel-a (Feb 7, 2013)

Thank you for the information Drimacus

Though, this does not change the fact that NiCr HE are indeed very much suitable for working with gold,silver and copper. and also very cheap.


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## Drimacus (Feb 7, 2013)

The key to building a durable and long-lasting electric furnace using nichrome or kanthal is to keep the watt-loading of the elements low; at or below about 12 watts per square inch of element surface, and to use no thinner than 16 gauge wire. So far I've run my crucible furnace for more than 600 hours, much of it at 2000 degrees F. for up to 48 hours straight, and the element has yet to burn out, but if it does a new kanthal element is $20.


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