Borax and Cryolite flux for MLCC's the best?

[924T]

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

 

[4metals]

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"

 

[Harold_V]

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

 

[924T]

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

 

[924T]

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

 

[kurtak]

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

 

[4metals]

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.

 

[Harold_V]

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

 

[Claudie]

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 :|

 

[924T]

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

 

[etack]

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

 

[kurtak]

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/

 

[Lou]

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!

 

[kurtak]

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

 

[kurtak]

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

 

[goldsilverpro]

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.

 

[kjavanb123]

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

 

[Lou]

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.

 

[Platdigger]

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

 

[kjavanb123]

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