Separating Antimony out of the liquid lead - Who to do?

[Fzr1000]

Hello together,

I have one question to you:
My lead has a hardness of over 28 BNH with pencil test.
I have molten my Monotypes and sometimes there was a silver foam (Google translator tells me „foam/froth“ for my German word „Schaum“) on top of the liquid.
When I took this of and separated it my lead was going much softer to 22 BNH.

But I don’t know how to do this controlled.
What I have to do to make my antimony swimming as a foam on the top of my cooking pot?
Other way, what I did wrong that the foam wasn’t staying in the melted lead and separated from the rest?

Thank you, and sorry for my poor English.

[fredj338]

Better to trade it for soft lead. If you lived in the states, happily trade you 100#.

[ryanmattes]

I agree. The easiest thing is to get pure lead, and mix your hard alloy with pure lead to get the hardness you want.

The hotter your pot temperature, the faster you'll notice the stuff on the top (it's called "dross," I think it is similar to "schlacke").

Antimony does not dissolve (auflösen?) in lead. Tin also does not dissolve in lead. Both will float to the top of your melt, and you have to stir and flux to keep them combined.

However, antimony and tin in equal parts dissolve with each other, and form a solution: SnSb. That solution will dissolve in lead, but only as a small percentage of the mix. Maybe up to 5% SnSb to Pb.

So if you have a lot of antimony in your lead, mixing pure lead until you only have 2-3% antimony, and adding 2-3% tin should make a more stable solution, with a lower BHN.

But the easiest thing would be to just add pure lead until you reach the hardness you want.

Hope that helps.



Sent from my Pixel 5a using Tapatalk

[William Yanda]

"Antimony does not dissolve (auflösen?) in lead. Tin also does not dissolve in lead. Both will float to the top of your melt, and you have to stir and flux to keep them combined.": Ryanmattes

Wasn't this contradicted in a recent thread? I believe both Lyman and LASC were referenced stating the opposite.

Usually the quest is to get a harder alloy. If you can find pure lead, diluting your alloy, or using a fraction of it with pure lead would be an easier way to get where you want to go.

[JimB..]

When you melt monotype, or any lead, contaminants of all sorts float to the top. This is normal. You can stir the mix with a very dry wood paint stirring stick and add a little beeswax to help the contaminants float and the metals stay in the alloy.

I save what I collect from the top of the melt in a metal bowl. When I have a bunch I add it to a big pot and recover most of the metal.

I do not believe that you are removing significant antimony. I think that your monotype has hardened with age and that melting and casting restarts the aging process.

Can you obtain softer lead?
What hardness do you want?

[Dusty Bannister]

"Antimony does not dissolve (auflösen?) in lead. Tin also does not dissolve in lead. Both will float to the top of your melt, and you have to stir and flux to keep them combined."

This statement is not correct. Tin combines with lead. Tin combines with antimony. The three will combine into one alloy. Even if allowed to form oxide, the ratios will remain essentially the same. You may notice a foamy layer forming on the surface of your monotype as it is melted. That is due to the high amount of antimony in the alloy. Increase the temperature and flux and reduce and it will all go back into solution. Any dross removed will have some of the alloy in the trash, and adding that to the next melting of scrap metal is a good idea.

If the alloy you presently have is too hard and not suited for your needs, dilute the harder alloy with soft lead. Trying to remove one of the elements from the alloy, is not practical for the home caster.

[Larry Gibson]

What Dusty said ^^^^^^^

[popper]

Solubility of Sb in Pb is 4% @ 252C and 0% @ 2C. No, you can't 'cook' it out. Add low Sb lead.

[truckjohn]

What our OP is seeing is alloy "Floating out." Often, this is an indicator of the temperature being too low. The first thing that comes out is tin, then antimony. They come out as rich lead alloys - not pure metal.

If he wants to keep it in - run the pot a bit hotter, add some flux, and stir less...

If he wants to soften the lead, well, just keep drossing it real good and stir the heck out of it.

[243winxb]

To remove antimony, VERY SLOWLY bring up temperature till alloy just become liquid. What appears to be oatmeal floating on top is Antimony & Copper. Skim it off & then flux and test hardness again.

[JimB..]

What our OP is seeing is alloy "Floating out." Often, this is an indicator of the temperature being too low. The first thing that comes out is tin, then antimony. They come out as rich lead alloys - not pure metal.

If he wants to keep it in - run the pot a bit hotter, add some flux, and stir less...

If he wants to soften the lead, well, just keep drossing it real good and stir the heck out of it.


To remove antimony, VERY SLOWLY bring up temperature till alloy just become liquid. What appears to be oatmeal floating on top is Antimony & Copper. Skim it off & then flux and test hardness again.

In both of these cases the content of the liquid alloy and the semi-liquid alloy are essentially the same. The effect seems to be caused by the alloy down in the melt being slightly hotter than the alloy at the surface. Don’t take my word for it, skim some off and then have it and a sample from the melt compared. I did this, and I’ll tell you that the alloy is the alloy, there is no separating it in our backyards.

[243winxb]

Refining process for removing antimony from lead bullion. https://patents.google.com/patent/US4425160A/en


adding caustic soda and metallic sodium to form an antimony-rich skimmable refining dross comprising a sodium-antimony intermetallic and separating the dross from the refined bullion. Along with antimony, other elements, such as arsenic, cadmium, copper, nickel, silver, sulfur, selenium, tellurium and zinc, if present in the bullion, are also removed in the dross by the sodium

:smile:

Never, ever add anything to the lead pot, other then an approved flux.

[M-Tecs]

Refining process for removing antimony from lead bullion. https://patents.google.com/patent/US4425160A/en



:smile:

That process is well beyond the means of the average home caster to accomplish.

Caustic soda is commonly called Lye. Lye is very mild compared to metallic sodium http://www.kplintl.com/blog/sodium-metal-facts-dangers-and-safety-precautions/

[Rickf1985]

To remove antimony, VERY SLOWLY bring up temperature till alloy just become liquid. What appears to be oatmeal floating on top is Antimony & Copper. Skim it off & then flux and test hardness again.

This is how you remove zinc, not antimony!

There is some real bad info circulating in this thread!!!!!! Very unusual for this forum.

[Rickf1985]

Refining process for removing antimony from lead bullion. https://patents.google.com/patent/US4425160A/en



:smile:

And it is nowhere near as simple as your method in post #10 would suggest. Not something that should be tried without knowledge of chemistry and reactions.

[Kavein]

To keep your mix in solution try topping your pot with burnt wood shavings. Oxygen will mess with your mix. If you want to reduce hardness just add pure lead. I guess the question is what is your target?

[JimB..]

Refining process for removing antimony from lead bullion. https://patents.google.com/patent/US4425160A/en



:smile:

Sodium is very highly reactive, so no doubt this works, but working with metallic sodium is very dangerous for exactly the same reason.

I doubt that you were actually suggesting that anyone try this, but if you do please take video!

[243winxb]

https://castboolits.gunloads.com/showthread.php?341960-Purifying-Lead-with-Caustic-Soda Harris process?

The simple method to reduce the % of antimony is, add pure lead to the pot. As said above.

Never, ever add anything to the lead pot, other then an approved flux.

[yeahbub]

Other way, what I did wrong that the foam wasn’t staying in the melted lead and separated from the rest?

Unless I miss your meaning, you are inquiring why your antimony is coming out of solution (separating from the alloy). If my understanding is correct, your alloy is tin-poor. If you add tin (Sn), your antimony will go back into solution. My linotype would do this when I was melting type metal I bought from the scrap yard. Then I realized the printing houses were selling it for scrap because it wouldn't easily cast into type anymore. Tin oxidizes into tin oxide quickly and the antimony begins to come out of solution. The higher the percentage of antimony, the more tin is needed to keep it in solution.

Not to worry about the English. Welcome to the website!

[popper]

Solubility of Sb in Pb is 4% @ 485F. That is frozen alloy! Melt solubility is much higher (10-12%). You can't 'cook' it out no matter what you can normally do. It will (same for tin) glob up in VERY microscopic chunks. You can't skim it off!!
Only thing you can do is add pure or a lower Sb alloy. Period. Yes it combines with tin but even SbSn doesn't skim off!

[Rickf1985]

Unless I miss your meaning, you are inquiring why your antimony is coming out of solution (separating from the alloy). If my understanding is correct, your alloy is tin-poor. If you add tin (Sn), your antimony will go back into solution. My linotype would do this when I was melting type metal I bought from the scrap yard. Then I realized the printing houses were selling it for scrap because it wouldn't easily cast into type anymore. Tin oxidizes into tin oxide quickly and the antimony begins to come out of solution. The higher the percentage of antimony, the more tin is needed to keep it in solution.

Not to worry about the English. Welcome to the website!

Then how do you explain antimonial lead with 5% antimony and 0% tin? According to what you are saying that cannot happen.
Or even better is Rotometals Superhard which is 30% antimony and 70% lead with NO tin. That is impossible isn't it?
As I said much earlier in this thread there is a LOT of misinformation in this thread.

[Larry Gibson]

When the alloy is in a liquid state the antimony is in solution and doesn't "cook off".

When in a solid state the antimony hardens first but is still mixed throughout the alloy, i.e. it does not separate in one local so it can not be removed.

It is as popper relates.

[Fzr1000]

Thank you all for your answers.
Now I took all of the removed material back into my melt and mixed it under the normally 5-6 BNH scrap lead from the range.
I got nearly 200kgs of range scrap again, so now I’m able to mix the Linotype down to softer levels.
No need to do more experiments like removing antimony.

[William Yanda]

Glad to hear of your success.

[bangerjim]

Glad you found your answer. That is exactly what I recommend and would do myself under the same conditions!

The Pb + Sn + Sb alloy is a eutectic 3 phase alloy and cannot be separated by you in your "kitchen" at home. The elemental metals combine at the molecular level and are very difficult to break apart by someone without sophisticated equipment and processes. It is a chem lab process for industry. Forget about it. You may be able to skim or "cook-off" a bit on the top, but your best bet is to sell it as-is on here or trade it for softer Pb alloy. Or dilute the HECK out of it like you did with pure Pb to get down to where you want the hardness to be.

Good luck!

banger

[243winxb]

Why do we Flux, if the metals don't separate in the pot? 1 fluxing and never needed again?

[Larry Gibson]

Why do we Flux, if the metals don't separate in the pot? 1 fluxing and never needed again?

The "scum" that accumulates on top is basically just oxidized alloy. When we flux the oxidized alloy is melted and assimilated back into the rest of the molten alloy.

[popper]

243 - the metals are sperate at the molecule level. What ever is at the proper temp and in contact with molecular oxygen will oxidize. It's usually just tin that has the lower liquid temp that oxidizes and we 'remove' the oxygen by 'fluxing' with a compound that removes oxygen (chemical reduction process). We 'cover' our melt with an oxygen 'barrier' to slow the oxidizing process. Burning sawdust requires oxygen and 'reduces' the oxided tin. Some compounds (flux?) when mixed into the alloy, bond to impurities and float to the top of the melt.
So fluxing can clean, reduce oxides and slow oxidation. The 'best' flux will do all 3. OK?

[243winxb]

Ok. I will keep fluxing.