home made cupels

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AgAuPtRh
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home made cupels

Post by AgAuPtRh » April 16th, 2007, 12:26 am

I've been reading up a bit on making my own cupels. Doesn't seem like the recipe is too hard -- or making the form to pack them.

Just wondering if any of you folks have tried this with any success and have some things to watch out for.

Mixing just the right amount of water seems like the first challenge.

Seems too that using a home made cupel just might add to few craked or broken experiments.

I'm thinking I can make a few and do some tests with just lead and no precious metal to see if I'm getting it right. I'll be doing a few things in the summer when the conditions are right to be playing around with fire and chemicals. One of my other projects will be a furnace.

Any info would be appreciated.

Thanks
Steve K

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lazersteve
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A few cupels.

Post by lazersteve » April 16th, 2007, 12:30 am

Steve,

You pay shipping and I'll send you a few free magnesite cupels.

Steve
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AgAuPtRh
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lazersteve

Post by AgAuPtRh » April 16th, 2007, 12:38 am

You're aaaalllllllright there Steve. Believe me -- you're a good man. I appreciate the offer -- I do however have several cupels on a shelf -- enough to hold me over while I experiment. heh heh !!!!!!

Tell you what though Steve -- to save on your idea for the newbie gift.

The first 5 newbies to post to your satisfaction are on me. I'll pay the shipping. Give me your address and I'll send a check or tell me how to send you some pay pal and I'll get that handled. ASAP.

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Newbie gifts

Post by lazersteve » April 16th, 2007, 12:51 am

I guess you've extended my contest to the first 5 newbies to post, No problem. I like the number 5 better than 4 anyway. GSP has already volunteered to pay the shipping. Maybe you two can split the bill. Now we really need a few unsuspecting newbies! :lol:
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AgAuPtRh
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shipping

Post by AgAuPtRh » April 16th, 2007, 1:03 am

was I not reading the fine print again???
didn't realize it was for the first 4.

I'm willing to pitch in and help whatever way I can.

I'll make a deposit for you on your video site. Hows that sound Steve. You use it whatever way you want.

Steve K

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Extra Pound

Post by lazersteve » April 16th, 2007, 1:05 am

Don't sweat it, I've got 50# of this stuff. I'll grow old trying :lol: to process it all.
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JOE S (INDY)
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Post by JOE S (INDY) » December 23rd, 2007, 1:38 am

Actually, I had a specific interest in home made cupels. Specifically powdered, burnt bone ones.

Anyone know what is used for the binder?
Joe

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Post by Noxx » December 23rd, 2007, 1:50 am

Maybe it's just pressed ?

I plan to try to make some magnesia cupels with my hydrolic press.
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Welcome to Indy- Bone Ash Cupels

Post by lazersteve » December 23rd, 2007, 11:04 am

Indy,

Welcome to the forum.

Here are a few links I located on making bone ash cupels.
  1. Bone Ash Cupels #1
  2. Bone Ash Cupels #2
The second link seems to be more detailed in my opinon, but I just skimmed a few pages of the book.

I hope this helps.

Merry Christmas,

Steve
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Post by JOE S (INDY) » December 24th, 2007, 1:48 pm

Thank you, Steve,

VERY helpful reading.

I have to say that I should have been smart enough to websearch for that - I guess it's just another one of those things you just have to learn to remember to do.
Joe

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Internet Research

Post by lazersteve » December 24th, 2007, 2:42 pm

Indy,

Don't sweat it, I enjoyed looking it up for you. I even saved a copy for myself. :wink:

Steve
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JOE S (INDY)
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Post by JOE S (INDY) » December 25th, 2007, 2:09 am

Steve,
That's exactly what I do on the Mining Forums.

Funny, on one forum you're a 'newby' and on other forums you are 'The Crotchity Old Wisened One'. Oh well, more to learn now.

Thanks again,

Joe
Joe

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Post by Harold_V » December 25th, 2007, 6:05 am

JOE S (INDY) wrote:'The Crotchity Old
I resent you stealing my title! :lol:

Harold

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Post by JOE S (INDY) » December 25th, 2007, 11:00 am

He, he!

Harold, the thing is that the title can't be stolen - you have to earn it one letter at a time.

Take Care and enjoy your Christmas!
Joe

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Post by Harold_V » December 25th, 2007, 3:15 pm

JOE S (INDY) wrote:Harold, the thing is that the title can't be stolen - you have to earn it one letter at a time.
Chuckle!

Well, I'm sure there's no shortage of readers that will attest-------I've done just that! I am, more or less, the resident curmudgeon.
Take Care and enjoy your Christmas!
Thanks, JOE S-------and, coming from the Scrooge I am, I extend the same to you!

Welcome to the forum, by the way. Always nice to see new faces.

Harold

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Post by aflacglobal » December 25th, 2007, 4:29 pm

Well there he is.
Merry Christmas Harold. :wink:
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Post by Platdigger » December 25th, 2007, 4:36 pm

Yea, Merry Christmas Harold......to you and yours!.....:)
Randy

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Post by Harold_V » December 25th, 2007, 8:33 pm

Humbug!

:)

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Post by Platdigger » December 25th, 2007, 8:57 pm

OK then, Happy HUMBUGGIN Harold!......:)

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Post by aflacglobal » December 25th, 2007, 9:09 pm

Merry Festivus Harold. :P
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home made cupels

Post by One Blanket » February 4th, 2008, 12:21 pm

I buy my cupels from Charles Butler in Bodfish california

he has a web site - - you can Google it. I don't remember the cost.
His torch assay video shows him making some; although I am pretty sure that he buys already made of late.
He does have recipes & instructions if you want to make your own.

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makeshift sustitute for cupel

Post by butcher » June 8th, 2008, 5:22 am

when not wanting to use up my good cupels I use sheetrock, cut two squares about 4 inchs. make dimple shape in one, sit it on other, can melt gold, copper, or silver on this with acytelene torch, sheetrock melts but at much higher tempeature than gold, after melt, can just push out melted portian grind an wash in water to get bead of metal if small bead, or pan it, I usually use this with flux of crushed glass,sodium carbonate (washing soda), flour,ect... sometimes lead litharge if assay, -----or just borax if just melting. this is not for fine gold or silver, i use my store bought cupels for that. ------- another trick cat litter clay makes a good refactory clay fer yer homade furnace when in a bind.

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Re: makeshift sustitute for cupel

Post by Harold_V » June 9th, 2008, 4:42 am

butcher wrote:i use my store bought cupels for that. ------- another trick cat litter clay makes a good refactory clay fer yer homade furnace when in a bind.
You might consider buying small clay melting dishes from a jewelry supply house in place of using cupels. Unless you're cupelling, I see no need to use them. Melting dishes have a considerable life span if you anneal and season them properly when new. You can expect months of service if you use them only occasionally. On a daily use basis, they last for weeks. There used to be a light brown clay dish available, which was not known for longevity. The ones made in white clay, sold under the Vigor name, will perform very well.

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Substitutes for cupels.

Post by catfish » June 15th, 2008, 11:21 pm

Hi Harold:

Just finished reading your post on, “substitutes for cupels”. I just purchased some new three inch melting dishes from Steve and would appreciate your advice on how to anneal and season them properly before I start using them.

I want to use these melting dishes for melting refined silver. I have dissolved several hundred grams of .925 and sterling jewelry in nitric and cemented it out with copper. I now want to melt some of the cemented silver into two ounce ingots to be used as an anode for a small silver cell that I am trying to build. I will be using my Argon electric furnace.

Any advice you could give me would be greatly appreciated.

Thanks in advance.

Tom

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Post by Harold_V » June 16th, 2008, 4:22 am

Tom,

Good to see you on the board.

My experience goes hand in hand with what I've read about the typical clay dish. They are quite stable if you heat them slowly at first, raising the temperature slow enough that entrapped moisture can evaporate. That prevents cracking. I used to place a new dish on a low flame on my hot plate and let is sit for maybe 15 minutes. I would then place it on a rest (block of asbestos in my case) and heat it with a rosebud, slowly, running the torch in circles around the dish. When the entire dish was up to a low red heat, I would then sprinkle borax on the dish and melt it with the torch. A thin film is all that is desired, otherwise when you pour off the values, flux goes with the metal. You'll come to realize how much is required the first time you use the procedure.

If you use your melting dish only on occasion, I suggest you always heat it slowly before putting it in service. They have a way of absorbing moisture when not in use----and are subject to cracking, much the same as a new one. That's pretty much the same procedure that is advised for graphite/clay crucibles.

Considering you'll be melting silver that has been recovered with copper, you'll get some copper oxide in the flux. That will make it get thicker and thicker each time you use the dish. The process of cleaning the dish using soda ash can be applied to rejuvenate the dish, although at a slight loss to dish thickness. Before cleaning is necessary, you can usually add more borax to the dish to keep it in operating condition. The flux coating not only absorbs some of the oxides, but also lubricates the molten metal so it pours well. When some starts sticking to the lip of the dish, it's time to refresh the coating.

I suggest you use borax glass, or anhydrous borax. It melts without all the frothing and blowing about that you get with the light, fluffy borax that is commonly available. Both do an adequate job, however, so it's just a matter of convenience. It isn't easy to find, and is not cheap, but it's worth the effort if you can find some.

Good luck! Running a silver cell is lots of fun. Make sure you have an adequate filter bag, so the slimes can't mix with the recovered silver. If you've used any of the silver for inquartation and have processed any dental gold, could be you'll recover some platinum and/or palladium.

Harold
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Preparing Dish

Post by lazersteve » June 16th, 2008, 8:40 am

Tom,

I have a video on my website that demonstrates the preparation of the dishes as per Harold's instruction. It's in the melting section of the videos.

Steve
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Post by Wyndham » June 20th, 2008, 12:37 pm

I suggest you use borax glass, or anhydrous borax. It melts without all the frothing and blowing about that you get with the light, fluffy borax that is commonly available. Both do an adequate job, however, so it's just a matter of convenience. It isn't easy to find, and is not cheap, but it's worth the effort if you can find some.


Harold, Anhydrous borax is not too expensive and can be found at pottery supply house in 1- to 50 lbs. Let me know where anyone is and I will try to find a co close by. Wyndham

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Post by Lou » June 20th, 2008, 12:52 pm

You can also make anhydrous borax just by heating the hydrated salt. Make a lot at a time, grind it up when cool in a mortar and pestle and save it in a tight bottle.


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homemade cupels

Post by bmgold » October 16th, 2008, 6:05 am

I have experimented with homemade cupels using bone ash moistened with a mixture of 1 TBS glue, 2 TBS sugar, and 1 cup water like Charles Butler teaches. I also replaced the bone ash with sifted wood ashes from the house heating furnace with some luck. It seems to work but sometimes gets pits that seems to shield the lead button from oxidizing completely and Mr. Butler told me that it could contain some gold that would give false assay results but for my learning experiments it is much cheaper than bone ash.
Anyone else try some substitutes for bone ash?

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cement cupels

Post by bmgold » October 16th, 2008, 7:49 pm

Sorry about a second post but I couldn't seem to get to the bottom of my last post to add more.
I just got a bag of mortar mix (cement only, no sand or gravel). I used a cupel mold bought from Charles Butler of ButlerLabs to press out some tiny cupels for torch assaying and tested them out. They really should have been dried first but I was just testing them out so I torch dried them and added a small lead bead from some action mining flux and some crushed ore known to contain gold. The lead oxide didn't soak in as well as a real bone ash or magnesite cupel but it may have been because of not being fully dry or maybe I used too much oxygen in the torch flame but it did result in a small gold bead.

I also tried using a larger cement crucible made months ago to assay this sample and it worked o.k. I don't know if I would want to risk a large amount of gold with this homemade stuff but it worked for my testing and it was a lot cheaper than store bought ones.

It seems like a waste to spend a dollar or more for a cupel to get a penny or less of gold but for a real assay it may be worth it. For doing quick tests for yourself, this works for me.

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