home made cupels

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One Blanket
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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.

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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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Post by qst42know » October 17th, 2008, 6:14 pm

Mortar mix already has sand in it. You must find plain Portland cement. It will be marked as such. It is the binder in concrete and mortar mix. I bought an 80# bag several years ago at Home Depot for about $6. I am still working from that bag. Controlling the moisture to make these is vital to prevent splitting.
I have also used straight Vigoro brand bone meal from the garden center. These work in smaller sizes just pressed with no additives and then roasted to ash to drive off the fats present. These will smell bad a lot like burning hair. Roasting after pressing reveals the ones that will split in use. They soak lead like nobodies business but are limited to about 1"diameter or less. Larger sizes will need a binder of some sort.

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Post by bmgold » October 18th, 2008, 9:53 am

Yes, you are right about the sand. I got the mortar mix for free since the bag was ripped and spilled. That would explain the glassy look when I tried cupelling a small test.

I got some store bought (action mining) cupels and tried one out with the torch. One problem I am having is silver. I want the nice gold color in my tiny beads but after trying a larger sample I think I have silver since there was a considerable amount of "sprouting" on my last attempt. Either my lead I used was contaminated with silver or my melting cup (made from cement a year or so ago) is contaminating my tests with silver from previous tests (likely).

I did try the straight bone MEAL and it did work but smelled bad and again a tiny silver colored bead. I have no nitric acid and won't pay the hazardous shipping fee to get some so I have no way that I know of to part the beads. They are mostly almost microscopic except for the last one. I've been saving all my tiny cupels to someday recover the precious metals and hopefully even the lead. I've tested the lead oxide layer in some with a reducing flame and can get the lead to reform into metal form again. I don't want to just throw them away since they contain some gold/silver/etc. and I figure the lead oxide is probably more dangerous than the lead metal. No since contaminating the Earth any more than I have to. The lead does form some really pretty colors on the sides of the cupels. I can see why it was/is used in paints.

Thanks for the great forum full of great knowledge and great people. Keep it up everyone.

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Post by qst42know » October 18th, 2008, 1:47 pm

The text I have on the subject is: "A Manual Of Fire Assaying by Charles Herman Fulton". This was a college text from Penn State back in 1911. The older texts have much more info on making your own stuff, from furnace construction for several types of fuel, to making cupels, and formulating your own fluxes. The commercial made cupels are likely more reliable for accurate scientific assaying, but for experimenting with the process home made will work fine. This book is well worth looking for. You may be able to find it at your local library.

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Post by butcher » October 19th, 2008, 8:59 am

bmgold read this forum for ways to make your nitric for parting,

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A Manual Of Fire Assaying

Post by jimdoc » October 19th, 2008, 3:52 pm

Here is a link to that book;

http://www.archive.org/details/manualof ... 00fultiala

There are also alot of the older books on the site.

Jim

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Post by bmgold » October 19th, 2008, 4:20 pm

Thanks for the link to the book and the link to e-bay nitric acid. The nitric was expensive but the shipping was WAY less than other places I checked. Probably won't be buying any but it's nice to know it is there. As for the book, I have it downloading now. This forum is full of great people!!!

Back to the homemade cupels and my silver problem: I still think I have silver but not as much as I thought. My lead "sprouted" as it cooled down when I moved the torch away before the process was done. I thought only pure silver would do this but I seem to be wrong (Admitting it is the first step to a solution) My real problem is I'm just working with too small amounts of precious metals. With a magnifying glass and good light I can find TINY beads in the cupels, both the homemade and the store bought ones so I just have to back up and start over. The process does work and it don't make gold where there is none. I'm probably the only one on the forum that tried to get to the end product too quick.

Thanks again everyone for making this kind of information available for little more than the cost of time to read and study.

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Post by viacin » October 19th, 2008, 4:52 pm

bmgold wrote: link to e-bay nitric acid.
:?: Where is said link? I would like to see this. I've searched a few times but found nothing.
Of all the contrivances for cheating the laboring classes of mankind, none has been more effective than that which deludes them with paper money. - Daniel Webster

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Post by qst42know » October 19th, 2008, 5:40 pm

If your flux is balanced and your assay is going correctly your PM will be quite pure, nearly round and sitting just barely touching the cupel, it will be attached but not strongly. Almost like a bb in a teacup. If your bead of metal is flat and firmly bonded to the cupel it is a sign that you havent removed all the base metals.

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Post by bmgold » October 19th, 2008, 7:09 pm

I guess I should have ordered it when I saw it (E-bay nitric) I can't find it again either and I don't even see the message I got the item number from.

Maybe I made it up or maybe I've been breathing too many lead fumes :?

It was from a company that also sold biodiesel making supplies. Maybe if somebody really posted then deleted the message they can jump back in with more info. I think the listing was ended but there was other auctions or buy it now sales (I thought)

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Post by qst42know » October 19th, 2008, 7:29 pm

I looked at the nitric acid auctions when the subject first came up. Now they don't even show on the completed side (and it has not been that long ago) which tells me the auctions were scrubbed by eBay perhaps by governmental request.

Shades of big brother.

Without a buisness that requires it, You'll have to make what you need. Till they put a stop to that as well.

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Post by viacin » October 19th, 2008, 8:43 pm

lol, gotta watch those fumes bud...

maybe no one has any for sale at the moment. I still see HCl and sulfuric acid for auction, although for almost twice the price you pay at the hardware store.
Of all the contrivances for cheating the laboring classes of mankind, none has been more effective than that which deludes them with paper money. - Daniel Webster

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ebay nitric

Post by bmgold » October 21st, 2008, 5:54 am

I found the link again on nitric acid on ebay. It has ended but WAS on there. I didn't make it up afterall.

260268502825

Username : dudadiesel

Keep watching this user or maybe send him a message to get another batch listed. Maybe he is just out now or didn't get any responses or maybe he will list more soon

Just a thought

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Post by viacin » October 21st, 2008, 6:37 pm

hey, thanks for finding it. That's the same guy that sells sulfuric acid too. 1 gallon for $56 is cheaper than anything I've seen, but still not as cheap as making it yourself.

He says "does not ship with bases", like sodium nitrate. But I wonder if he has thought about shipping it with his sulfuric acid. If it spilled out and mixed with the cardboard box he would have a big 'ol batch of guncotton :p
Of all the contrivances for cheating the laboring classes of mankind, none has been more effective than that which deludes them with paper money. - Daniel Webster

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Re: home made cupels

Post by DarkspARCS » June 9th, 2013, 8:46 pm

ok... fine. I'll be the first n00b to post here. Laser Steve, is the offer of free cupels to the first 5 n00bs who post here still good? :P :twisted:

We're almost out and we have so much ore testing left to do lol... :roll:
Thanks for your time

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Re:

Post by AndyWilliams » June 9th, 2013, 9:27 pm

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

Harold
Nonsense! You're the crochEty one, kind of like the difference between Sodium Metabisulfite, and Sodium Metabisulfate!

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Re: home made cupels

Post by Pogo » September 30th, 2013, 7:36 pm

Hello,
This comes from my book; Fire Assay, by Orson Cutler Shephard and Waldemar F. Dietrich Copy right 1940: Portland cement alone is sometimes used for assay cupels; it is more commonly used with various percentages of bone ash. When cement is used as all or part of the cupel composition the amount of mixing water should be 8 to 12 per cent. Less or more cause the cement to check or crack on heating. Pure cement cupels give higher cupellation loss than do bone ash cupels, but mixtures of cement and bone ash up to 75% cement give as low a percentage of losses as those made of pure bone ash. Have fun!

P.S. It took me two years to puzzle out how to perform a fire assay. I found this book in a Colorado used book store about four years after (I thought), mastering the process. This book has helped greatly, is probably one of the books you'll never find in the library, and goes into fire assay with such scope and depth that I feel overwhelmed.

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