Sorry to disagree, Ilcop, but overheating is the culprit here that's causing those colors.Originally Posted by ilcop22
The reason the ingots have the streaks of gold & blue is that the lead was poured at too high a temperature when the ingots were formed. That lead will have more dross and oxides in and on it, but simple fluxing will remove that easily.
The rub is that, as others have noted, the same temp for one alloy may well be too high for another.
Hope this helps, keep us posted.
I appreciate you and others clearing that up, sagacious. I wasn't getting the picture when I posted that comment. Its raining today, so hopefully I can try tomorrow.
On that note, if I have the melt too hot and then lower the temp, will the color change back to normal. Is the "damage" already done?
Who keeps not his arms in times of peace, Will have no arms in times of war.
-Gaelic Proverb
The dross color will not change back by itself after the heat is reduced-- but that's OK. The gold/blue/purple color doesn't indicate any "damage" per se. But it usually means that the melt is far hotter than necessary for pouring, and should be allowed to cool down a bit. Generally the lead need only be about 50-75*F above melting temp for pouring bullets. So, if you happen to see the melt turning funny colors, just back off the heat a bit, and flux the metal with wax, sawdust, or whatever you're favorite flux is. Then you're right back where you want to be, with no damage done to the alloy. After reducing the heat and fluxing, the colored oxide dross should not return, or do so only very slowly.
Now, sometimes folks will crank up the heat in order to get "good fill-out" of the mold. This is not always the best solution, since higher temps can cause more surface oxide to form, and that itself can hinder pouring as the session progresses. Almost always, thorough and proper fluxing, combined with good pouring technique and lead/alloy selection, and proper melt temp will provide a better solution than overheating the melt. Also, bullets poured at high temp will usually be slightly smaller in diameter than bullets poured at 75*F above the melting point of the alloy. If you want the most from your mold, it's best to pour at the lowest temp possible, and not the highest temp possible.
This is one of the reasons that some master-craftsman bullet-pourers have been pouring very consistent high-quality bullets for years or decades... without the benefit of a thermometer. With a lot of experience, one can keep pretty close tabs on the temp of a known lead alloy by simply noting the changes in color and pouring characteristics, etc. The lead will tell you what it's doing.
Good luck and let us know how it goes.
Last edited by sagacious; 09-25-2009 at 06:50 PM.
Not long ago, I mixed some stuff in a potful of lead that turned out to be some of that fake pewter. It had beautiful colors, some of those you describe, all at one time in swirls on the top of the pot. Icouldn't get it out of the lead, either after I mixed it. Iturned my pot ot lead to the thickness of cooked cream of wheat, and sort of grainy. I had to turn the Pro Melt up and pour it out, as it wouldn't come out the bottom pour spout. Makes a fine door stop in a coffee can! I hope someone hasn't mixed some of that stuff in your lead.
Cast Boolits, Where lead balloons go over....
Yeah, I got some of that crud also.
It does thin out by adding pure lead to it. Kinda a waste though. I use it in my paper patched loads so the hardness does not matter that much. I target shoot.
I have it to almost being workable. I diluted that stuff with lots of lead.
It caught me by suprise.
Pewter must be kept very close to it's melting point. If it is overheated, it will do exactly what you described-- your description is a good one. Pewter will turn all kinds of colors and evolve and aggressively-forming frothy or foamy dross when kept too hot.
If you mix much pewter into your lead, you must turn the temp way down. Adding pewter will drop the melting point of the lead alloy dramatically, and you should only pour at about 50*F above the melting point. If you keep it at a temp suitable for pouring pure lead, it will rapidly turn into a pot full of frothy, clumpy dross. At that point it becomes difficult to deal with, and fluxing still results in a lot of metal loss.
Keep the temp low. Turning up the heat only makes it worse.I had to turn the Pro Melt up and pour it out, as it wouldn't come out the bottom pour spout. Makes a fine door stop in a coffee can! I hope someone hasn't mixed some of that stuff in your lead.
I find a lot of pewter at yard sales, and I buy all I can find cheap. It works very well as an alloying component, but one must treat it as it wants. Only as hot as necessary, and not hotter is the goal.
Hope this helps, good luck!
Upon considering this topic, I think you should do an article on this topic, sagacious. You seem to know a lot about heating the melt - Something I think all new casters could benefit from. Be a good sticky.
Who keeps not his arms in times of peace, Will have no arms in times of war.
-Gaelic Proverb
Alchemy- where do I find some?
I'll go with those who say- pure lead.
For the past 40 years I've had and used quite a few different sources of "pure" lead. Without exception each produced that blue/purple sheen with hints of bronze/copper hue (almost sounds like a wine tasting snobfest
ilcop22 ...
I had a similar experience a few weeks ago . I bought a couple hundred lbs of lead from my scrapyard .
It was lead that was used for "cauking" pipe joints way back when. It was used with the large 8" + cast iron water service lines .
It is typically what you would call "plumbers lead".
This lead all came from the same jobsite.
I melted the first 100 lbs, and did not pay attention to the heat , i also got the
"pretty rainbow colors" you spoke about .
Asking a few questions , i was told that it was probably real pure lead , and i had overheated it to cause the colors.
The colors even showed up a bit in the ingots.
A few days later , i melted the rest of the pile , and paid attention to the heat .
I didn't get it any hotter than needed, that batch showed no colors on the top of the melt and even the ingots had a different , shiny , look to them .
Hope this helps .
Joe.
And the verdict is.... (drumroll, please): Pure lead!
I started out by doing the "drop test". The pan ingots both as they came and after I poured them a new were dull if not a "thud" sound when they hit concrete. My other ingots (with tin) pinged like a fine wine glass.
I then heated 3 pounds of the pan ingots. I started super low - No melting. I eventually heated it up to the point where it melted, but was chunky. I.e. not hot enough to fully melt. I got it up to the minimum melting temp where the melt was smooth enough to pour, still not hot enough to come clean of heated tools. And guess what happened? Gold color on the top. This lead was at the bare minimum melt temp. No purples and blues, though.
I then tried fluxing the gold dross back in - No good. Floated back to the top. Ended up throwing it in the dross bucket.
Conclusion: Pure lead that I was heating too much. No tin. Still not sure what the gold color is. This lead was "cold."
Who keeps not his arms in times of peace, Will have no arms in times of war.
-Gaelic Proverb
Thanks for the explanation, sagacious. I recently melted 300 # of what I know to be 99% pure lead and observed the color changes as described. I wondered at the time the reason for it but thought it probably had to do with the temp. Using the fish fryer/propane burner, I had failed to reduce the temperature as the pot emptied. Some of the ingots retain the bluish color on the surface, which I assumed was some form of oxide.
Good job, Ilcop22. I very much like your experimental approach.
"Pure" lead is very prone to the oxide colors (gold hue, or blue and purple) you describe. Pure metals have higher melting points than their basic alloys, and so pure lead-- since it must be heated to 620*F to melt-- is more prone to this heat-accelerated oxidation than ww lead (melting point 500*F +or-) or linotype (about 470*F).
Just curious, what compound are you fluxing with, and what is your fluxing procedure?
Last edited by sagacious; 09-30-2009 at 11:23 PM.
This IS one of the better threads in quite some time. Another vote for "sticky-ing" it.Upon considering this topic, I think you should do an article on this topic, sagacious. You seem to know a lot about heating the melt - Something I think all new casters could benefit from. Be a good sticky.
I don't paint bullets. I like Black Rifle Coffee. Sacred cows are always fair game. California is to the United States what Syria is to Russia and North Korea is to China/South Korea/Japan--a Hermit Kingdom detached from the real world and led by delusional maniacs, an economic and social basket case sustained by "foreign" aid so as to not lose military bases.
The thread is now sticky
John
Wow okay great! I've been freaking out since yesterday over these dang colors and I just knew for sure it was zinc. Since I was running hot there would be a possability I could have gotten zinc in my alloy while melting wws. So now my question is what are the indications you have zinc in your alloy???
OH84, if you have too much zinc, you'll know it, as your pot of what you thought was good casting lead turns to the consistency of oatmeal. The higher the zinc levels, the worse it gets.
Me, I'm kinda puzzled at all this hand-wringing over a little surface layer of oxidation. Since I'm a bottom-pour guy these odd colors and minor crud on top of the pot bothers me not at all. As the Lyman handbook points out, once a layer of oxide is present on top, oxidation underneath this pretty much ceases. This is why we blue our firearms--bluing is just a thin oxide coating, that is rust--and helps prevent rust from going deeper into the gun metal. In the case of our lead pot, a thin layer on top does pretty much the same thing.
This is a great thread, and the explanation of the various color schemes is enlightening.
lathesmith
Sure, I reckon it's possible you melted a zinc ww when smelting. But gold and blue and purple coloration is not an indication of zinc in your alloy. What you saw is normal.
As Lathesmith noted above, if there's zinc in there, you'll likely have fill-out problems. Don't fret about zinc unless you're really having problems with pouring-- and then what you need to do is describe the problems for someone to help with a cure.
Lathesmith,
I agree with your comments. This is indeed true. The oxide on top need not present much hassle to one using a bottom-pour pot. Providing, of course, that one does not continually add more ingots during the casting session.
If that happens, then oxides will be dragged down from the surface and entrained directly into the melt. This is one of the reasons why it's routine practice to flux after adding more ingots to the pot. If one fills the pot and uses only what lead is there during that pouring session, then there's usually no need to flux until the beginning of the next casting session, and after the new ingots have melted.
Where the entrained oxides reach a certain amount, it can present pouring problems, especially with small-cavity moulds. If one is having problems with a small-caliber mould, flux the melt and then try again. That often cures the problem.
One place where these entrained oxides really cause serious frustration is for people pouring small-volume lures and small jigs for fishing. The small gates/sprues and tiny cavities in those molds are often very sensitive to entrained oxides (and the pure lead recommended by lure mold manufacturers is very prone to oxidation), and poor fill-out can result.
When pouring small-capacity moulds, and especially with a dipper, be suspicious of entrained oxides when fill-out takes a nose-dive. Fluxing generously, once or twice as necessary, is very often the solution.
Hope this helps, good luck!
I didn't get that worded right , I mean't that I had to upend the pro-melt and dump it out, not that i had to turn the heat up.Pewter must be kept very close to it's melting point. If it is overheated, it will do exactly what you described-- your description is a good one. Pewter will turn all kinds of colors and evolve and aggressively-forming frothy or foamy dross when kept too hot.
If you mix much pewter into your lead, you must turn the temp way down. Adding pewter will drop the melting point of the lead alloy dramatically, and you should only pour at about 50*F above the melting point. If you keep it at a temp suitable for pouring pure lead, it will rapidly turn into a pot full of frothy, clumpy dross. At that point it becomes difficult to deal with, and fluxing still results in a lot of metal loss.
Keep the temp low. Turning up the heat only makes it worse.
I find a lot of pewter at yard sales, and I buy all I can find cheap. It works very well as an alloying component, but one must treat it as it wants. Only as hot as necessary, and not hotter is the goal.
Hope this helps, good luck!
I still have some of that junk. I'd send a chunk of it to someone if they can tell me what it is. I bought it at a pawn shop , advertised as pewter. It is much heavier than aluminum, and is about the color of aluminum
Cast Boolits, Where lead balloons go over....
Great thread. I did the same thing with WW's today. I did not reduce the temp as I was casting the ingots. I kept noticing this gold that would then turn purple/blue. I am hoping that I can try to heat it up again very slowly because when I noticed the colors I had my pot on 10(high).
So if I let it cool, heat back up very slowly, and I notice just gold color then this means I am okay to go? Should I flux again? Seemed like no matter how many times I fluxed I could not remove the blue/purple stuff.
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