I have a new graphite crucible and electro melt furnace. Does a graphite crucible have be coated with flux the same way as an open ceramic crucible before you use it. I am assuming that I still add flux to the melt just as I do with an open ceramic crucible. I have left this question with the manufacturer, but they don’t seem in a hurry to answer it. Thanks for any help…Rob
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I’m not sure, but I believe Graphite deteriorate fast with Flux and even Borax.
And it is important to minimize the contact with air.
One of he benefits of a graphite crucible is that the carbon combines with any oxygen present to create a reducing atmosphere within the crucible, helping to protect your metal, similar to how you would cover an open crucible with a flame. Coating the interior of the crucible with a barrier would prevent that.
I have always used my furnace crucibles as-is and have had good results.
The crucibles do slowly get consumed. Some years ago an Orchid member said he weighed new ones and re-weighed them with each new use so he’d know when to retire them. I suppose worst case would be a honeycombed crucible having its bottom break down, especially when you stir the melt. They do get porous with repeated use.
Neil A
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Neil and Yggdrasil…Thanks! I know about the crucibles breaking down with use and that they product a reducing environment. I just hadn’t reasoned through using a flux. I need some sheet and now I can make it with my new furnace. I will report the results…Rob
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Rob, there is a temptation I am sure you are wise enough to resist to look down into the furnace to see how the melt is going. I use a small hand mirror. I generally see a small soft flame at the bottom covering the melt, something like burning alcohol. That must be the graphite burning.
You know but beginners should be aware that one should be wearing green lenses when looking closely at molten metal.
Have fun with your new furnace.
Neil A
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Hi Rob,
I am excited to hear about your furnace experiences!
i have my friends new melting furnace, and my own crucible…but i gave yet to get up the courage to try it…
i have printed out the manual and read alot of forum posts…and typed out detailed notes and cautions…
i am waiting to buy the KC ingot mold from PepeTools…they have been on backorder for awhile…
so, being impatient, i recently purchased the smaller of the two Durston open ingot mold…(i am looking for an ingot mold solution that has a large sprue hole)…i tried pouring 2 ounces…but it did not fill the. bottom…rather it pulled up…maybe i was not hot enough in the melt…or mold…
since i cannot melt 4 ounces with my smith little torch, and this open mold has a large opening, i may try my friends furnace…i think i will need 4-5 ounces…
i will probably end up using delft clay like you!!!
keep us posted on your process!
julie
Hi,
here is what 2 oz looks like in my Durston smaller open mold
(3-1/2” x1-1/4”x1-1.4”)
(90mmx35mmx35mm)
i think i rolled the longer one…it was probably about 20% shorter lengthwise
julie
Hi,
maybe i should have gotten the graphite open mold…i thought about it…it is smaller…
1.85”x1.10”x1/2”
(47mm x 28mm x 12.7mm)
i would love to hear about these graphite molds…any feedback would be appreciated…
i probably should have just gotten the defft clay!!!
julie
My first pour seems to be a good one. I used 96.6 grams of scrap. I normally don’t keep a piece if it is more than two years old. The furnace was up to temperature in 8 minutes. I let it soak for 5 minutes and then poured. My mold is an adjustable sheet mold that was my Dad’s. I give it a wipe with 3 in 1 oil and then heat it until it smokes, then keep it warm with a torch until I pour. The only real tense moment, other than possibly burning the house down, was pouring. It has to be quick. Give it a try Julie. Just make sure that the furnace is burned in and practice your pouring motions before you do it for real…Rob
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Hi Rib,
so you kept that furnace after all?…what does the top/ inside of furnace look like?
so your pour was 3.3 ounces…nice…ingot surface look good?
remember my past post asking why some of my ingots had big snowflake crystal surface pattern?…well, i read somewhere that means it has big crystal metal structure…(? from too hot metal temp…?…if i recall correctly?
julie
I am rolling it out now. I will let you know how it goes…Rob
Hi Rob,
I have a quick question…is it ok to leave the metal melt in the furnace for a period of like 15 minutes of so?
i am trying to pour ingots for sheet…I would prefer a closed mold, a large pour spout, and not have to heat up the mold…
this is leading me toward delft clay…
so…I am trying to think the process thru in my head…
lets say i melt 8 oz of sterling silver, to yield two 4 oz ingots
(melting furnace capacity is 1kg (35 oz)
i pack a mold
i get the metal up to the proper tempurature
i pour ingot #1
i put the crucible back into melting furnace to get it back up to temperature
and pack mold #2
is it ok to have the melting metal sitting in the melting furnace for say 15 minutes while i pack mold #2?
or is it better to just melt 4oz for mold #1, use it up, and then pack mold #2, and then melt metal #2
please advise your thoughts,
julie
Julie…All I can tel you is that someone stopped by when I was melting the pour for the ingot that I posted and the melt stayed in the furnace for about 15 minutes. My guess is that, as long as you keep the lid on and maintain a temperature just above the melting temperature, you are fine. I am interested in guidance on exactly what temperature set the furnace at for various metals and how long to keep it at that temperature once the metal is melted. The references that I look at are all over the place. Good luck…Rob
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Hi Rob
(I did not mean to imply that i saw snowflake crystals on your ingots…the recollection just popped into my brain while i was typing, haha)
julie
So far it has rolled out fine with no bad spots. I always polish a piece of sheet from an ingot first to find any bad spots before I cut it up and use it. It is now part of a piece that a customer has asked me to make that is a duplicate of one that I made several years ago. I find making duplicates of what was a one of a kind to be very time consuming, especially when I have to cut and polish a duplicate stone. I may refuse to do it in the future. I will post a picture when I am done…Rob
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Following are pictures of my first piece from the first furnace melted ingot…Rob
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Hi Rob,
i am curious to know what you set your melting furnace temperature to? …1832F…?
and no flux, just a carbon rod to stir?
julie
Silver is liquid at 1640. I set my furnace to 1850. Probably a little high, but you can’t be sure that what your furnace is reading is what the melt is at unless you let it soak for a long time. So far so good. I will probably use 1800 in the future…Rob
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In one of our recent discussions about melting metal, someone mentioned the need for welding type goggles or a mask. I have one specifically for welding, but I can’t see using it when melting metal in an electric furnace. The last time I did this, I looked into the very hot crucible to stir with my graphite rod and was struck by how bright it was. Should I be wearing some sort of eye protection other than a clear face mask? I have no idea what type of harmful light is being emitted. Thanks for any thoughts or suggestions about goggles (and lens color and number) to wear over prescription glasses. Thanks…Rob
I would recommend IR shade 3 at minimum, shade 5 is probably better if you spend a lot of time looking at melt temperature metal. There’s a lot of IR spectrum in there that really isn’t long term great for the eyes.
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