# Borax and Cryolite flux for MLCC's the best?



## 924T (May 31, 2014)

In several different GRF threads that discuss smelting ceramic substrates (MLCC's, catalytic converters),
it was emphasized that chemical leaching would not achieve the same percentage of recovery of PGM's as smelting.

The 2 main ingredients for a flux for smelting MLCC's seem to be Borax and Cryolite, with Silver as the collector.

Will Borax and Cryolite alone (with Ag as collector) get the job done, and if so, what ratio of one to the other should I use?

Also, I've seen negatives about Carbon contaminating Pd, so wouldn't a graphite crucible be all wrong for
smelting MLCC's?

Wouldn't molten Cryolite attack a graphite crucible?

Thanks for any commentary/help on this, as I really do want to get the processes correct for pursuing Pd in MLCC's,
and it's appearing that smelting and then leaching is the optimum route to take.

Cheers,

Mike


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## samuel-a (Jun 1, 2014)

Mike,

I have smelted a friend's MLCC's about a year and a half ego.. Since i couldn't find any reference in the literature, i came up with the following flux recepie:
The flux used was premixed 9:1 Borx(dec):fluorspar. The ratio of flux to mlcc's was 1:1.

The MLCC's were not crushed. I have placed the MLCC's in a graphite crucible and brought the gas furnace to about 800-900C. At this point the flux was slowly added via a makeshift auger until all of the calculated amount was added.
Using a steel rebar with a weldded half moon; 30-40 minuted later the flux would still be quite fluid and no capacitors had been felt on the bottom.
When done, the slag and metal was poured into an angle bar mold, welded shut on both ends. (see pic)

There's no need to use collector this way, there's enough metal already.
keep note, that this flux is highly acidic and react violantly with the ceramic substrate, so the first additions are done slowly.
The resulting rods were sent to Metalor for further refining.




Good luck


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## 924T (Jun 1, 2014)

samuel-a,

That's exactly what I was looking for----thanks for weighing in with a fast response!

Were you using actual Fluorspar from Iceland?

Your post is the first I've heard or seen of an 'angle mold' (thanks for taking the time and trouble to put
your picture in your post----this is a case of a picture is worth more than 1,000 words).

It looks substantially more cost effective than a cast iron 'cone' mold. Do you preheat the angle mold prior
to performing a pour, as you would have to with a graphite mold?

Cheers,

Mike


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## samuel-a (Jun 2, 2014)

Yes, a picture in this case is indeed far better than i could have explained it.
I was looking for proper cone mold but were very expensive so i have to improvise. I too never seen this anywhere else.

The mold was seasoned with a layer of soot from a torch and pre-heated prior to pouring.

I have no idea where did the Fluorspar came from.

One more note to the process, once the first few additions of flux are done, the temp' was lifted and maintained at 1200C +- for 30-40 minutes.

After visual inspection of broken slag pieces, the slag should not hold any metal beads, or at least small amount of beads near where the metal button/rod.

There's a reason why you never seen this info before and I have kept this process to my self for too long. Hope you and others could make good use of it.


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## kjavanb123 (Jun 2, 2014)

Hi Samuel,

Please advise if the same flux formula can be used to extract metals from incinerated ashes??

Thanks
Kevin


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## 924T (Jun 3, 2014)

Sam,

I'm extremely grateful you not only took the time and trouble to respond to my post, but were generous enough
to share what turns out to be several innovations you came up with!

I had been gritting my teeth about having to drop $200 or more for a cone mold; I am definitely going to be
talking with a buddy of mine that welds, and try to duplicate your angle molds.

How did you go about calculating the size of your angle molds before you made them? That in itself is a bit
of a story within the story.

Do you mind sharing the dimensions of your angle molds? And what/how you preheat them?

Also, it's like you're reading my mind------I got on the forum tonight with the purpose of asking you
if you preheated the angle molds, and if you used any coating or release chemical-----and your answer
was already there! That's the kind of stuff that just keeps me pumped up about the GRF----innovation
everywhere, and experienced people that are willing to help the less experienced members out.

My pursuit of MLCC's has gotten me over the hump of not having a defined sense of purpose regarding the pursuit of
precious metals----I ordered in (and just received a few days ago) Hoke's book-----it's time for me to get serious about having some (safe) fun with all this, and the only way to be safe is to become informed, and then get some experience. I'm on page 25 now, having only scratched the surface of all that content.

I have 10 kg of MLCC's (no resistors in with them) waiting for me to get all the right glassware and chemicals in, and now, also, to get a Kerr MaxiMelt in. My plan is to experiment by running the process you've shown in your videos, lazersteve's
process, and now to also smelt and run the resulting rods through your and lazersteves's processes, and note 
as many details as possible along the way, and then compare final results at the end (running 1 kg each time).
Fortunately, I have just enough MLCC's that if I really screw things up, I can get advice and analysis here on the GRF,
and then run the experiments a second time.

Cheers,

Mike


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## samuel-a (Jun 19, 2014)

Dear Mike,

Sorry for the very late reply..... my time is extremely limited lately.
I'm glad i could help.

As for the mold, don't bother yourself with the size and volume, it really doesn't matter. Just produce the largest your work bench and budget allows you to. It will pay off one day.
Make sure wall thickness will not be thinner than 1/8", other wise you risk piercing it.

Do note, seperating Bi and Sb from Pd is no easy task.

Good luck. 

Sam


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## necromancer (Jun 19, 2014)

samuel-a said:


> GNS - e-scrap yield list v1.0 (link fixed)



file not found, i think i have asked about this in another post a long while ago, thanks samuel-a


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## samuel-a (Jun 19, 2014)

try now


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## 4metals (Jun 19, 2014)

I always liked to add soda ash as well. I noticed Samuels formula listed borax as (dec) is that in reference to decahydrate? I always used anhydrous borax as it does not foam up. 

I liked 2 parts borax, 1 part soda ash and 1/4 part fluorspar. Equal volume to what you are melting.

And yes it does eat crucibles. 

I always preferred to grind the ceramic to a powder before melting so it mixes better and reacts faster. Less melt time equals less attack on the crucibles. 

I would try without any collector first, see what size bar you can get, then do a re-melt of the slags using a flux of 1 part borax, 1 part soda ash and 1/8 part fluorspar. You can add some silver to this to see if you pick up any more values by using a collector, I never needed a collector. 

But remelting the slags even without a collector is common, collects the loose beads.


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## Irons (Jun 20, 2014)

It took me a while to find a good source of Cryolite. It turns out that Cryolite is used in some ceramic glazes. It was a pure white powder, not the dirty natural material. Good stuff. Check with your local ceramics supply house.


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## 4metals (Jun 20, 2014)

source of cryolite

http://www.washingtonmills.com/products/cryolite/


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## Irons (Jun 22, 2014)

4metals said:


> source of cryolite
> 
> http://www.washingtonmills.com/products/cryolite/



Sheffield Pottery http://www.sheffield-pottery.com

..has 5 pounds of Cryolite for 12 DollarsUS.


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## 4metals (Jun 22, 2014)

Sorry, I got carried away, Washington Mills only sells 50 pound bags. 

Remember, even 12 pounds is enough to eat crucibles quickly, be conservative.


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## 924T (Jun 22, 2014)

Irons and 4metals,

I was going to inquire as to the appetite of Cryolite for Graphite, and you were way ahead of me!

Lmine has a 50 lb. bag of Cryolite for $58.99 http://www.lmine.com/category/flux_components.html,
but I don't know if it's the natural stuff or the white kind.

I'll definitely be starting out with a smaller quantity, like the 5 lbs. Irons mentioned.

I was also going to inquire about remelting the slag, and you were ahead of that one, too.

I did find a picture of melted Borax (forgot to bookmark it), which saved asking the question of whether
it's transparent or not------------in the picture I saw, the poured-and-cooling Borax looked yellowish------
is that what I should be expecting to see when I've finally melted some?

Lmine also has anhydrous Borax, 55 lbs., for $54.20 (same link as above). Is that a pretty competitive price?

Cheers,

Mike


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## 4metals (Jun 22, 2014)

Cryolite is sodium hexaflouroaluminate it is a synthetic compound made to mimic the natural Kryolite which is mined in Greenland. Natural Kryolite is usually a grey to reddish grey powder (I have seen it more grey and more red so it varies) Cryolite is white. 

Looking at the Legend website I do not see Cryolite but I do see fluorspar which is calcium diflouride. 

In my experience, Cryolite is far more effective at dissolving alumina substrate materials (ceramic) than flourspar. They both eat crucibles, fluorspar is used as a thinning agent for flux, cryolite is for dissolving ceramic materials in a melt. 

Years ago I used to dissolve the gold off of granulated ceramic substrates and save the stripped substrates to send them to a large smelter in upstate NY. They would melt 4 drums of substrates at a time in huge furnaces and add borax and a secret ingredient which they never spoke of and melted for about 12 hours. I think they only melted that long so I would fall asleep waiting but that's another story. Anyway when it came time to pour, out came lots of liquid slag and only the last bit was metal. Everything was liquid for the pour. 

Since then I have melted ceramics instead of the acid process and recovered all of the mixed metals which went into the refining circuit. Much less acid used that way!

As far as pricing goes for anhydrous borax, that seems fair but depending on where Rock Island is, freight may be an issue.


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## Irons (Jun 23, 2014)

The Cryolite from Sheffield is a pure white powder, about 200 mesh with no lumps. It's as nice as you could ask for and blends perfectly.

4Metals is right. A little bit goes a long way. 5 pounds will last most people a long time.


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## kjavanb123 (Jun 30, 2014)

Today I tried formula mentioned in this post, here is the scope,

60g mixed MLCCs and SMD resistors.
2 part borax
1 part sodaash
1/4 cryolite

Mixed them well and dropped MLCCs into graphite crucible, added the flux on top,and let it melt in my cupola furnace for 20 minutes, during of which I took the crucible out and swirled it for better mixing. I poured into angeled iron mold and here are the result



I am thinking I should have left the crucible longer inside the furnace but it seemes to produced two large beans of alloyed metal.

Thanks
Kevin


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## 4metals (Jun 30, 2014)

Melts like this require a long stay in the furnace. Usually after a time in the furnace some of the slags are dipped out and poured over a flat surface for inspection to determine how long it is taking for the metals to begin to join together and sink to the bottom. When you reach that point you pour off the top half of the pool of slag and continue to add new fluxed material. 

This is where 2 things are very important. 1. is to use anhydrous borax so it does not swell up as it releases its water, and 2. is to use a scrap / flux mix that is thoroughly dry. 

When you pour off the slags inspect them to make sure they are glassy and free of beads. This is repeated until there is a decent pool of molten metal in the crucible. When you pour the entire melt, the metal is the last to come out and it is of a much different appearance than the slags while pouring. 

It is common to have a slag remelt day where all of the slags are re-melted until liquid and given time for all of the remaining beads to settle out before pouring. 

If you are processing a consistent stream of scrap, the mixture is fluxed in bulk and it is easier once you determine the time for slagging off and the addition rates. Then it is just a repetitive thing, pour flux off, new mix in, in timed cycles.


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## Irons (Jun 30, 2014)

I've found that, when processing an unfamiliar material, to do a small test batch, and like 4 metals said, see how long it takes for the material to give up the values. It's better than making a mess with the whole batch and trying to figure out how to clean it up. Trying to recover everything on the first pass may not be economical, so pouring off half the flux and adding new material is a good idea. I plan to have a dedicated Ball Mill, just for blending the flux with the ground material to give a homogenous charge. Right now, I do it by hand and the results aren't always even, plus, it's time that could be applied best elsewhere.


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## 4metals (Jun 30, 2014)

Irons is right, as he always seems to be, don't let that Gabby Hayes look fool you!

Milling the material in with the flux is the best way to assure uniform mixing. Mix it all with your standard flux mixture in the correct proportions and do a test melt.


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## Irons (Jun 30, 2014)

4metals said:


> Irons is right, as he always seems to be, don't let that Gabby Hayes look fool you!
> 
> Milling the material in with the flux is the best way to assure uniform mixing. Mix it all with your standard flux mixture in the correct proportions and do a test melt.



Dag Nabbit. :mrgreen:


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## samuel-a (Jun 30, 2014)

4metals
You are correct, by 'dec' i indeed meant decahydrate, and i do agree anhydrous is preferable.

-------------

However, with respect... i disagree with the suggestion of adding soda ash and the result is somewhat evidente by the picture uploaded by Kevin. From my experianc, the slag does not seem like it should - i.e. glassy and thin without shot embedded in it. 
There could be number of reasons other than the flux mixture of course; temp', time in furnace, mixing, metallic constituents.

Kevin, You mentioned you included resistors, those are composed mainly from an alumina substrate and have some organic encapsulation. This can aslo lead to troublesome smelting.

I would encourage you to first incinerate (if resistors are included) and try and replace the 1 part soda ash with silica or 50:50 Li2CO3:SiO2, rise the smelting temp' , have a longer smelt time. Then pour and obseve the result.

My 2 cents.


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## Lou (Jun 30, 2014)

Kevin needs to be pouring into a conical mold.

Fluorides are best for alumina/zirconia/titanates; carbonate works well for silicaceous materials.
SiC seems to handle fluoride baths OK.


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## 4metals (Jun 30, 2014)

I think a 60 gram sample is too small to base your formulations on in the first place. Second for what he is trying to accomplish the melt was not long enough for the cryolite to effectively do its job. Cryolite melts at a high temperature and that is where it does its work on the substrate ceramic. 

A cone mold is always preferred for test melts and slag remelts but for melting the actual lot, molds are required. That is because I have seen countless times a refiner pour a cone mold (a classic conical cone mold) too full and end up with a bar that does not fit into any crucibles. Whoops! 

I prefer cone molds made in a conical form over the vee shaped bar molds, the conical shape forces the molten metal down from all sides and effects better collection, especially when it is a small metallic fraction to begin with. For years I used a square mold tipped on end to form a vee and had results like shown in the picture, (beads not in one metal mass but un-joined) then I switched to a true cone mold (conical) and the same flux scenarios resulted in solid uniform beads. 

Silica alone, or in combination with only borax, is not a suitable flux because of the high melting point of the silica. Mixing silica 1:1 with soda ash will lower the viscosity and the melting temperature. If you want to try Samuel's suggestion, use a 50:50 mix of silica and soda ash in lieu of straight silica.


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## Irons (Jun 30, 2014)

Use Acidic Flux to attack Basic substrates and vice versa. 

Alumina= basic
Silica= acidic.


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## 4metals (Jun 30, 2014)

Well, mixing the acid silica with the basic soda ash yields a neutral flux component. 

The borax will make the melt acidic and the borax will function to liquify the melt and lower the slag formation temperature. With high melting components like cryolite and alumina that really makes a difference. 

Cryolite is a neutral flux. So you will still end up with an acidic flux. The alumina acts as a basic component. The theory here is to add enough alumina material to keep the end pH alkaline although measurement is all but impossible. This is because an alkaline slag will reduce the temperature required for complete liquidity. 

Unlike assay fusions where a flux is measured by its reducing power on the lead we want to avoid lead as a collector or any other metal additions if possible. 

If you notice a scum like gangue floating on the melt that indicates you have not burned the material completely so additions of sodium nitrate will burn that away for you by generously donating its oxygen to the combustion. This again is something you don't want to go overboard with. Better to burn completely up front. I have melted material that I could never seem to get rid of the scummy layer in pretreatment by adding 5% sodium nitrate to the mix. It behaves better as a component in the flux than it does being tossed on top. 

As you can imagine it is important to learn the behavior of individual flux components and how they react with your blend. For this reason processing large homogeneous blends where you can mess with the flux components on a sample basis and get it right for the production run is critical. 

Unfortunately this kind of refining comes from more "been there done that" than reading. I cant tell you how many times I've singed eyebrows, burned off my arm hairs, and melted my shoe soles just to get a sample of the molten slag. 

You have to arm yourself with the knowledge of the make up of what you are melting and apply the knowledge of what different flux components do and work out some test scenarios. After a while it gets easier. (and the hair grows back too!)


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## kjavanb123 (Jul 1, 2014)

All,

Thanks so much for your valueble responses. I got them after I remelted the material from my yesterday smelting, and this time I cooked it for an hour and swirled it few times during that time. Poured the melt into angeled mold and it looks like this,



And closer look reveals that tiny beads had time to consolidate into this,



There was a hole in crucible right in the middle of my second batch, thankfully the level of melt was below it, so nothing was loss, I am going to use your advises tommorow.

Regards,
Kevin


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## 4metals (Jul 1, 2014)

One of these would work wonders now.



And when you really get going, these are for slag remelt day.



Both available from Legend

Years back, when I had to slag off during a melt, I used the big cone mold and made a slight inclined ramp about 6" high and tapering out about 6 feet. Then after slagging off I poured the molten slag down the ramp where it cooled. Often a small puck of metal was at the bottom, it hardens long before the slag, that was thrown back into the melt. By pouring the slag on to the ramp it was much thinner and a hammer would break it into manageable pieces. The last thing you want to work with is huge cones of solid slag from the big mold.

I was melting in a small Cutter rotary furnace but its capacity was huge, The refractory lining (no crucible) was 3 feet in diameter and 6 feet deep. We had to pour out 5 o 6 cones to empty half of the slag. I probably could have stopped the rotation before slagging off and avoided any metal pour off but as it behaved nicely and collected in an easily recovered puck, stopping while in the process wasn't necessary.


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## 4metals (Jul 1, 2014)

I went hunting in my files to show you what a rotary tilt furnace looks like. Unfortunately these were from before the days when everyone had a camera in their phone so regretfully, I have no photos.







The unit operated in a horizontal position and it rotated slowly at about 1/2 a revolution per minute. The flame shot right down the center and the rear had a charging door which could be opened while in operation to add material. The unit tilted down to pour from the nose. 

The entire unit was lined with refractory brick and mortar so care was always taken to assure a flux mixture with the least effect on the refractory. Even then we had to reline once a year. But that was melting every day, 5 days a week for 10 hours. I always blended and fluxed enough material to assure I could process for 10 days on one flux formulation. 

In the assay lab, my favorite hang out, I tried different flux proportions and blends on the mix to see which had the lease effect on the refractory while doing the required reduction and pooling of the values. I did this by having thin slices of the refractory brick cut which looked like tongue depressors in both size and thickness. These were added to the fusions and relative comparisons of refractory wear were made to choose the best result with the least effect on the lining. 

Because of the way this thing worked, with the flame shooting towards the opening in the front, we had troubles with fines blowing right out the front of the furnace. We overcame this with a briquette making press which pressed out flux sweep mix into pellets 8" around and a foot long. They melted as quickly as the powder and solved the dust issue. 

This was one hot furnace to run. It required the operator to suit up in the "tin man suit".


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## Irons (Jul 1, 2014)

I bet that furnace wasn't very efficient from a fuel consumption standpoint. That was back in the Day when gas was 20 cents a Gallon.


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## 4metals (Jul 1, 2014)

The newer designs have the pour out hole in the center so the heat can stay in a bit longer and be more efficient.




But gold was under $300 back then too!


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## FrugalRefiner (Jul 1, 2014)

4metals,

Thanks for sharing that glimpse into the world of the commercial refiner. 

Dave


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## Irons (Jul 1, 2014)

4metals said:


> The newer designs have the pour out hole in the center so the heat can stay in a bit longer and be more efficient.
> 
> 
> 
> But gold was under $300 back then too!



I like that Lazy Susan for the Cone Molds.


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## 4metals (Jul 1, 2014)

If you notice that Cone Mold Lazy Susan has hinged cone molds that flip up to a stop so the contents can slide out and it flips back down for a refill. Each of those molds holds about 5 gallons of slag.

Unlike this run of the mill boring Bar Mold Lazy Susan. (With pretty blue mold release)


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## Irons (Jul 1, 2014)

That's still above my Pay Grade. :mrgreen:

OK, I see how that setup works now. Thanks for the explanation. :idea:


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## kjavanb123 (Jul 13, 2014)

All,

I dissolved the metal alloy produced from smelting mixture of SMD capacitors, resistors and few Ta capacitors, in dilute nitric acid, the solution has turned to green color as can be seen in the qtip, stannous chloride test showed a little of yellow color which could be Pd, and some undissolved residue that could it be Ru? Or Ta? Further testing will be conducted, as I read Ru is insoluble in nitric acid.

Here is the residue left from filtering the nitric solution,



And qtip result after adding stannous chloride to green solution,



Will post further updates soon.

Thanks
Kevin


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## 4metals (Jul 13, 2014)

Refining the alloy you produced in the smelting process is a totally different topic than this thread originally addressed. I suggest you will get more input by reserving this thread to follow up on the smelting process and open a new thread for refining the smelted alloys. 

That will make future searches easier and more informative.


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## 924T (Aug 19, 2014)

Samuel-a,

I forgot to ask you how you measured the temperature of your gas furnace?

Type K thermocouple? Laser thermometer? Other?

Were you using the same furnace with the Kaowool that you recently posted a video of?

Cheers,

Mike


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## 924T (Aug 19, 2014)

Irons,

My budget for acquiring lab glass is temporarily depleted, so I'm back to the flux approach, and
will be ordering my first 5 lb. bag of Cryolite from Sheffield tomorrow.

I'm not sure there is an affordable graphite crucible for running a 1kg batch of ceramic capacitors,
since it would become 2 kg. with the flux mixture added, which would require quite a large crucible.

I feel like a just got a college education, reading the exchange between you and 4metals, about smelting.
Many thanks to the both of you!

It sounds like I might be better off utilizing a medium-sized crucible, and periodically pour off the
slag, and then add more capacitor/flux mixture to the melt.

If you have a favorite brand/type of graphite crucible, I'd sure like to hear about it.

Cheers,

Mike


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## 924T (Aug 20, 2014)

4metals,

How did you preheat those massive cone molds?

Was the incline that you poured molten slag onto made of steel?

After rereading your posts in this thread, it appears to me that smelting is as much an art
as it is a science.

And, you were correct, it wasn't Cryolite on the Lmine website-----I had hit too many websites that
night, and everything had become a homogenous mental mix.

Cheers,

Mike


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## 4metals (Aug 20, 2014)

Those big cone molds, and the "smaller" ones on the lazy Susan are for de-slagging so they see mostly flux and make the retrieval of the accumulated metal (if any) easier as it settles into the cone. 

The big cone mold on wheels, which the guys used to call the chariot, was preheated with a propane asphalt torch like the hot tar roofers use.

The molds on the lazy Susan were placed under the pour spout and got warm enough so the flux and metal never stuck. Since a metal bar (if you call a cone mold shape a bar) is not desired, the molds did not need the preheating you would do if they were receiving a full metal charge as they were filling up mostly with slag. 

Remember cone molds are not made to be filled with metal, more than one refiner has had the "what do I do with this now" moment after filling a cone mold and realizing the resulting metal chunk doesn't fit into any crucibles they had. Not to mention just how heavy a copper based bullion slug is that came out of the chariot cone mold. (Don't ask me how I know this!) 

Yes the incline was made of cold rolled steel welded to shape. It was painted with a mold release to prevent sticking but after enough applications it seemed to become "nonstick"


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## Harold_V (Aug 21, 2014)

I had considerable experience with cone molds, having used them in three sizes. Aside from not filling a large one with metal, so it can't be remelted, the only real concern is that they are preheated enough to not contain moisture. Molds, pretty much any mold, that have been sitting idle for a prolonged period of time are prone to absorbing moisture, a condition exacerbated by living where there's high humidity. It's a good policy to heat them at least to the boiling point, to ensure there are no steam explosions when pouring. That's an experience you can live nicely without. 

In order to eliminate oxidized copper from my cement silver, I fluxed when melting, then poured to a cone mold. I made sure the resulting buttons were not too large to fit my #8 crucibles, to avoid that problem. Using a cone mold simplifies the removal of slag, as the surface area of the button in contact with slag is quite small. A smack with a hammer was often enough to cleanly separate the two. Once cleaned, I'd remelt the resulting silver buttons and pour my anodes, flux free. 

If you use a cone mold as I did, it's a good idea to coat the interior with lamp black, as, under the wrong conditions, the silver can fuse to the otherwise unprotected surface. Makes for a rather interesting project, removing the silver!

Harold


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## 924T (Aug 22, 2014)

4metals,

Many thanks for the reply--------I had been puzzling over just how you would heat up something that 
large and dense-------a roofer's torch, eh?

I think I remember seeing one or more of those on the Red Dragon website.

Since you mentioned some welding was done to your slag ramp, was it to add low 'sidewalls' to it?

I was trying to visualize that ramp last night, and began figuring something would be needed
to prevent the molten slag from running over the sides of the flat metal.

Cheers,

Mike


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## 924T (Aug 22, 2014)

Harold_v,

I do, in fact, live in a very high humidity area, about 3/4 mile from the Mississippi river, so your
commentary about heating/drying any kind of crucible is taken to heart.

Also, I'm glad you mentioned the lamp black----I don't have an Acetylene torch, and have been waffling
between deciding on lamp black or a can of aerosol Teflon to lube the molds with. Since you have had
success with the lamp black, I will go with that.

And, prior to signing in tonight, I was at the Lmine website checking prices on budget graphite
crucibles, and had somewhat settled on either a #6 or #8 as very practical sizes to own. I was glad
to see you had used crucibles in that size range, with good success.

Here's an unusual question: If I were using a 2-torch (propane) small furnace to smelt in, would it much matter
whether the crucible was square or round? 

I'm guessing that it would be more cost effective to make a square or rectangular crucible than a round one,
because it would eliminate running the graphite on a lathe to make it round. If that would translate to a lower
selling price, knowing now that the flux will, over time, destroy the crucible, that would permit one to be able
to have a better backstock of crucibles on hand.

Cheers,

Mike


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## kurtak (Aug 22, 2014)

I use a propane turkey fryer burner to preheat my cone mold - also I use cooking oil to season the mold

what I do is put the cone mold on the turkey fryer while waiting for my melt/smelt to take place - I then put about an inch & a half of cooking oil in it - when he cooking oil starts smoking I use a basting brush to bring the oil up on the side (inside) & it starts forming the carbon layer on the mold walls - when I am done pouring my melt/smelt I re-treat the mold again with cooking oil (kind of like you season cast iron cook ware) to keep it from rusting

As you can see in the pic the inside of the mold is in good shape & the last time I used it was about 6 weeks ago & it has been "very" humid here in Wisconsin for those six weeks

Kurt


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## 4metals (Aug 22, 2014)

The ramp did have 2 or 3" high sides to keep the slag from flowing over the side. The sides extended all the way to the end which was flat on the floor. Only about 4 feet was sloped and 4 feet was flat on the floor. 
I used cone molds solely for separating small quantities of metal from large quantities of flux so sticking was never an issue. The furnace room was always very warm so not humid at all. I would still pay attention to what Harold says about preheating and coating the mold with soot. Those 2 precautions will never disappoint you.


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## Harold_V (Aug 22, 2014)

924T said:


> Also, I'm glad you mentioned the lamp black----I don't have an Acetylene torch, and have been waffling
> between deciding on lamp black or a can of aerosol Teflon to lube the molds with.


You'd be well served to avoid using Teflon of any description when they will be exposed to the temperatures one encounters in melting of metals. 



> And, prior to signing in tonight, I was at the Lmine website checking prices on budget graphite
> crucibles, and had somewhat settled on either a #6 or #8 as very practical sizes to own. I was glad
> to see you had used crucibles in that size range, with good success.


I sized everything around a #8 crucible, which I found to be adequate for the level of operation at hand. I'd caution you, however, to avoid pure graphite crucibles. They're very expensive and do not respond well to being fluxed. You'll get better performance from graphite/clay crucibles, and even better performance with silicon carbide crucibles. Note that any crucible used in conjunction with a flux is going to experience a reduced life expectancy.



> Here's an unusual question: If I were using a 2-torch (propane) small furnace to smelt in, would it much matter
> whether the crucible was square or round?


First, you must make a distinction between melting and smelting. It is unlikely (but not beyond reason) that you would smelt, which is the process of extracting values from ores. If you are simply melting existing metals, that's what you're doing. Melting. 
I can see that from the position of one without a lathe that a square crucible may make more sense, but they don't. I have yet to see anything but round crucibles, and that's likely for very good reason. If nothing else, square corners present stress risers, and offer a place for failure. If you are thinking of something made of metal, you'll going to have to change the way you think, as metal vessels for melting are not acceptable, not even for aluminum melting, although with a refractory coating they can be used with success. Molten metals are strong solvents and will readily dissolve other metals, even at temperatures well below their melting points. 

Harold


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## Claudie (Aug 22, 2014)

Even on cookware, Teflon is a bad idea. There is too much money involved to see anything on the news about it but the fumes from heating Teflon can be toxic.

http://en.wikipedia.org/wiki/Polymer_fume_fever :|


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## 924T (Aug 23, 2014)

Claudie, 

You're absolutely correct!


From my personal archives, something I had completely forgotten:

One time I lived in an apartment that had an electric stove, and I used to sit my Teflon frying pan on 
a burner set on low to dry it off after washing the pan.

One night I had to rush out for some reason, screwed up and set the burner on high, and didn't get
back for at least an hour. 

The fumes were terrible, and I was sick and had impaired breathing for a few days------it was not fun.

Now that I've remembered that debacle, I can testify that both your and Harold's advice are spot on!

Cheers,

Mike


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## etack (Dec 3, 2014)

If you are to use the flux described in the thread what crucible would you use. Fused Silica Crucibles, fire clay, or Silicon Carbide. 

I think I want to give this a try.

Eric


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## kurtak (Dec 6, 2014)

etack said:


> If you are to use the flux described in the thread what crucible would you use. Fused Silica Crucibles, fire clay, or Silicon Carbide.
> 
> I think I want to give this a try.
> 
> Eric



I have been using these for my smelting :arrow: http://www.morganmms.com/crucibles-foundry-products/crucibles/ultramelt/ & have been happy with them 

I will get at the very least 3 furnace runs out of them (aggressive flux, high temp & long run time) & as many as 6 or 7 (less aggressive flux, lower temp & shorter run time)

I would not trust fused silica or fire clay for more then one smelt (if that) with this aggressive flux, high temp, long run time process

Edit; to ad --- keep in mind you are dissolving "ceramic" in the process 

Kurt

Edit: Opps - I posted the wrong crucible page link above - those are crucibles I have been considering trying --- these are the ones I have been using :arrow: http://www.morganmms.com/crucibles-foundry-products/crucibles/salamander-super/


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## Lou (Dec 18, 2014)

Kurt, you're only getting 3-7 runs out of _those_ silicon carbide crucibles?
The heck are you smelting? :shock: 

I'd be inclined to think 10 X more lifespan at the minimum--they aren't exactly cheap!


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## kurtak (Dec 19, 2014)

Lou said:


> Kurt, you're only getting 3-7 runs out of _those_ silicon carbide crucibles?
> The heck are you smelting? :shock:
> 
> I'd be inclined to think 10 X more lifespan at the minimum--they aren't exactly cheap!



Opps - my bad - I meant these have been the ones I have been using :arrow: http://www.morganmms.com/crucibles-foundry-products/crucibles/salamander-super/ 

I was "looking" at the Ultramelt crucible's as a possible for my next purchase - based on what you are saying I think I will spend the extra money as I do a fair amount of smelting

My flux for the most part is soda ash/borax/fluorspar - I tend to go a bit more then 50% soda ash more like 55 -60% with a couple tablespoons of fluorspar per quart flux

What gets hard on them is that "sometimes" I also add a "bit" of potassium nitrate to insure bum up of any carbon that may not have got complete reduction in the incineration process of the material being smelted --- maybe that's not necessary :?: --- I do it (as insurance of not loosing values) as I had read about it a couple years ago when doing research on smelting & flux's

Kurt


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## kurtak (Dec 19, 2014)

I should also maybe add that in my first post I was talking about the number of time's I would use the crucibles for smelting --- due to the large amount of flux when smelting along with running at higher temps & longer run time then when melting there comes a point were I just don't want to trust them for more smelting --- at that point (based on how the inside walls look) I will get a few more use's out of them for "melting" cleaner metals 

My common practice is as follows

1) when a crucible looks like it is only good for "maybe" one more smelt I put it on the end of "smelt" life shelf (but still good for some melting)

2) because of potential PMs hung up in the slag on the crucible wall's it now gets used for "one" (maybe 2) silver cement melt(s) to collect those PM's - which are then recovered in the anode slime of the silver cell

3) it then goes on the "for melting base metals" shelf to be used for melting base metals recovered from waste solutions (copper, brass, etc.) or even zinc which I pour to shot to use for cementing PGMs from chloride solutions --- depending on condition at this point & metal being melted I will get another 1 - 5 use's out of them (with 2 - 3 being the common usage)

Will try to post some pics of crucibles at different stages of life in the near future

Kurt


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## goldsilverpro (Dec 19, 2014)

My last furnace would hold a crucible as large as a #20 comfortably. For general work, I used a #16. For pouring pure silver into bars, I used a #6 or #8. I always used 1-man charging tongs to handle the crucibles. Here are a couple of hints, learned the hard way, to make the crucibles last longer.

(1) Storage. Always store the crucibles, whether new or used, in a Dry, Warm Area. When they absorb moisture from the air, they can become very weak. A couple of times, when I tried to remove a large loaded crucible from the furnace with the charging tongs, it tore about a 3" x 4" chunk out of the side of the crucible. This is less apt to happen using tongs that grip the entire crucible. However, after storing the crucibles properly, I had no problem with the charging tongs

(2) When I started making silver bars, I would add the same amount of silver to the crucible for each melt. After awhile, I noticed that, at the silver surface level, a deep indentation was forming on the inside of the crucible. After that, I varied the amount of silver in each of the melts.


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## kjavanb123 (Dec 19, 2014)

CM Hooks, metionens 50% soda ash, 40% borax, 10% broken glass (optional), this is mixed with ceramic materials at 2:1 ratio, then for each lb of ceramic materials using an oz (28g) of flourite. I will try this mixture with a catalytic converter honeycomb tommorow, and use silver as collector and copper qs collector in another test, then send them both and slags for PGMs.

If silver is used as collector, when electrolyzing it, will part of Pd goes to the solution or co deposit, but if copper is used, then we would not have the same issue.

Regards,
Kevin


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## Lou (Dec 19, 2014)

I try to keep the glass out of the flux unless necessary to thicken the flux.

Kurt, if you want success, you might want some dry silver cement and ball mill that with the catcon and flux mixture.

As for your electroparting question--yes, Pd can co-deposit. Usually happens at a low pH value in the cell. I think you'd be fine so long as the voltage is kept low.
http://www2.bren.ucsb.edu/~dturney/port/papers/Modern%20Electroplating/12.pdf

Now, the fate of the Pt from silver collector systems--I always to try to avoid? That I would be curious about. I know Pt nitrate will not plate out on titanium even at high voltage--you get a mixture of Pt oxides/hydroxides. 


If there is just Pd in solution with silver, probably the best bet is to bring the pH up to 6.5 on a hot solution, filter the Pd(OH)2 and other hydroxides, then dissolve in dilute HCl, filter to remove any AgCl, wash the Pd off as best as possible, concentrate that solution and go after it any which way. The AgCl can be converted back to metal, and re-used. Probably not a bad idea to take a melt sample and dissolve it and see how yellow/brown it is. 

Probably copper is the best bet, followed up with a little copper sulfate cell.


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## Platdigger (Dec 19, 2014)

I am curious if copper or silver will collect all of the rh.


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## kjavanb123 (Dec 19, 2014)

Lou,

Thanks for your advise. I found a very good article on using copper as collector metals which I will post it in my first try smelting cats.

Regards
Kevin


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## famerise (Jun 2, 2015)

4metals said:


> source of cryolite
> 
> http://www.washingtonmills.com/products/cryolite/



Although they offer fire brick, http://refractory-brick.com/fire-brick.html. You can contact them to find some sources of Cryolite. I cut it 3 times and it is short.


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## autumnwillow (Nov 3, 2017)

I'm sorry for posting on a very old topic.
Where could I find cryolite? I mean in what kind of shop? 
Aside from sodium hexaflouroaluminate does it have other names?

I cannot buy heavy items directly from the US as this will cost a lot of money just to get it shipped to my country.


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## snoman701 (Nov 3, 2017)

Pottery supply...look for one that supplies art potters. 


Sent from my iPhone using Tapatalk


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