Mysterious Exploding Lead Pot

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John Alexander posted this 01 February 2020

My lead pot exploded 15 minutes ago. What a mess.

This won't be a very useful safety warning though, unless I can figure out the cause.

I was spooning sprues ( some probably still warm) into the unplugged but still molten pot as I dipped them out of a metal coffee can with a tablespoon.  As far as I know exactly as I have hundreds of times before, including once at about the same time yesterday. When boom and about half an inch off the top of the full pot flew in all directions.  The only causalities were a flannel shirt, one lens of my glasses, and my pride.

I have a messy clean up of a variety of tools, the floor and eight feet up the window behind the pot. Don't know how the flying lead avoided hitting my face, the only bare skin available. My beard and old man busy eyebrows caught some of it but no burns.

There is never any water in the shop and wasn't any today except in me but I didn't have a runny nose and wasn't leaning over the pot.

The last bit of lead in the coffee can yesterday was dumped directly into the pot so it was empty today.  However, I did scrape up some of the bits and pieces of lead on the floor and dumped it in the coffee can today and my best theory so far is that a lost primer was scraped up with the lead near the pot. I don't drop many primers and am pretty anal about hunting them down. Also where I prime is about 8 feet from the lead pot but they are round and can roll. I suppose a spider, or other life form could have been in the coffee can. Any theory is better than none.

I would appreciate your thoughts on what might have happened so I can avoid a repeat.  Once is enough.

John

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Brodie posted this 03 February 2020

My friend Rubin used to cast commercially.  One night he emptied a bucket "containing nothing but wheel weights" , that a friend had given him.  That was the last time Rubin ever trusted lead from a "friend".  The bucket not only had live primers in it is also had live 45 acp ammo.  Rubin poured it into the lead reservoir of his master caster machine.  He left the basement shortly thereafter in a big hurry.  He was cleaning lead off of everything in that basement for a week.  I don't know what he did with his "friend", but I'll bet he never ever poured lead into that machine that he hadn't examined first.

B.E.Brickey

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MarkinEllensburg posted this 25 April 2024

I get hissing and popping just putting my cold skimming spoon into a hot pot. I do so very slowly. No visible liquid anywhere. That right there tells me that it takes a miniscule amount to cause a steam explosion. I don't want to find out first hand.

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Brodie posted this 07 February 2020

To keep live primers out of your lead sweepings just run a strong magnet through the sweepings.  It will pull out all the primers.  And for those who say the primer cups are non-ferrous try a magnet on them you will be surprised.  Most are only copper plated.

B.E.Brickey

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sluggo posted this 25 April 2024

I do my casting upwind outside. Years ago i think an insect maybe a bee? landed in the lead pot. Although a minor splash of lead dropplets flew out it was an unsettling event. My fire fighting buddy set me up with some nice gloves. I have gone through a few facemasks over the years. It took awhile to get used to the gloves but i did. I am ugly enough as it is.

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Ross Smith posted this 01 February 2020

It's most likely moisture from condensation off the floor. It takes very very little. If it's cold and you pour hot lead into your ingot mold chances are you've seen it bubble a few times. that's steam coming OUT of the cast iron. Water turns to steam at a ratio of 1:144 if I remember my long ago fire training. That's explosive. One drop would have emptied your pot. It's happened to me.

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stevebarrett posted this 01 February 2020

 

I had a similar experience, though not half so dramatic, not long ago. I had a pot of lead alloy I wanted to stir, and picked up my cheap wooden-handled stirring spoon off the shelf and poked it into the pot . A minor explosion as stuff spat out which I completely couldn't understand at all. There was no evidence of water anywhere around. My eventual suspicion was likewise, namely that an insect or something had been sitting in the spoon and I hadn't checked when I dunked into the mix.

 

Steve 

 

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99 Strajght posted this 01 February 2020

I have had this with a cold metal spoon or cold lead that I was adding. Not always but I do not do that any more.

Glenn

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Larry Gibson posted this 01 February 2020

"However, I did scrape up some of the bits and pieces of lead on the floor and dumped it in the coffee can today and my best theory so far is that a lost primer was scraped up with the lead near the pot."

Bet that is it exactly.  Did that a couple times in the past and learned to not put sweep ups in to molten alloy.  I'll pick out the larger pieces of sprue and put those in but not the "sweepings".

LMG

Concealment is not cover.........

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Mouldknocker posted this 01 February 2020

It is most likely caused from temperature differences. Never put/stick anything cold into, or onto molten lead. I preheat everything, always.

Pour molten lead into cold ingot moulds and you can get the same result.

The Tinsel Fairy is very sneaky indeed!!

Jeff

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Bud Hyett posted this 01 February 2020

Concurrence with everyone talking of primers in the mix, I've had that happen to me. The good thing was this occurred at the beginning of casting as the pot began initial warmup. Working to get ready as the pot warmed and suddenly there was a very loud boom and the sprues in the pot on top scattered. 

A spent primer may have enough priming compound left to explode again.  Not nearly the force of a new primer, but enough residual to cause a problem. 

I use cornmeal as a flux, it boils and bubbles when stirring it in. I've learned to set some cornmeal on the hot plate to dry and drive the moisture out as I begin the casting day. Then I have less boiling and bubbling as I flux. The boiling and bubbling comes from the corn oil within the ground corn.

Farm boy from Illinois, living in the magical Pacific Northwest

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John Alexander posted this 02 February 2020

I want to thank all who have suggested ways to avoid having another lead pot explosion. I think those suggesting various mechanisms that might have resulted in moisture getting into the pot would be strong theories if I still lived in Maine with it's sometimes high humidity.  I think it is less likely here in the desert.  The relative humidity was 30% that day.  Our furnace is in my enclosed shop area and the heat from the furnace keeps the shop temperature well above the outside temperature all winter long making it difficult to envision condensation from the outside air that gets in. None of my tools or molds rust anymore.

I think I found an additional clue as I was cleaning up the mess yesterday. After scraping lead off the area affected I swept things into one  area. After picking up what I could by hand I spread out the fine stuff and examined it under good light. I didn't find a live primer but I did find one shiny gas check and one spent primer both originating from the same area a dropped live primer would have come from showing that an unrecovered live primer could have made the same trip.

Whatever caused the explosion I will never again dump sweeping into a hot pot.  In spite of being a depression baby with a fear of letting a penny get away, any lead too small to pick up will go into the dross can and I will become even more obsessive about finding any dropped primers.  I will also avoid putting any porous or cold material into a molten pot.  One lead pot blow up is enough for a lifetime.

 

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Smoke Ratchet posted this 05 February 2020

What ever it was …...

I'll bet it came off of the floor. Very glad to hear that you were not injured.

Smoke Ratchet

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stevebarrett posted this 05 February 2020

 

I’ve been wondering about the undetected primer as a cause of the explosion, and it’s probably just my ignorance. If I’d been asked whether a primer dropped into molten lead would explode, I’d have had to say I just didn’t know. It’s obviously not something one is in the habit of doing, although I wouldn’t volunteer to try the experiment. Is there any evidence on this?

 

Steve

 

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Eutectic posted this 07 February 2020

I can tell you for certain that a primer in molten lead will go off pronto.The same thing happened to me. Fortunately I have a plastic shield in front of the pot. I was adding some alloy spatters I swept up.The amount ejected was not as great as yours, but the explosion was very sharp. I know it was a primer because I found a primer anvil in the alloy, I never did find the cup.

Steve

 

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Aaron posted this 25 April 2024

Realizing this post is 4 years old and Ed's last comment was as long ago, I felt the need to offer one more possible way of water introduction not mentioned in the post yet.

I cut sprues onto an aluminum cookie baking sheet on my right at crotch level, then drop the bullets onto a towel pad to my left. After casting halfway through a 20 pound pot, and having a large collection of sprue metal, I shake the cookie sheet to settle the sprue metal towards one end where I spoon it up and dump it back into the pot.

Now.....during the summer, when I do this casting, I get all sweaty. I have noticed on many occasions, despite my careful attention, drops of sweat fall onto the sprue pile of metal. Were this to go unnoticed, and were I to introduce this sweat laden metal back into the melt pot, a steam explosion would almost certainly occur.

Don't allow sweat to drip onto your mold, your sprue pile, or your casting tools. As much as I dislike looking like a 1980's workout person, I now use a headband if casting on a hotter day where sweat may form on my noodle.

 

With rifle in hand, I confidently go forth into the darkness.

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Premod70 posted this 25 April 2024

After a couple of witnessed slashes and one occurrence myself I never introduce anything into a hot pot. If adding to the pot put it in as the pot is warming. Moisture will steam out as the pot heats but as a safe guard I always try to stay away as the pot melts the lead alloy, you never know for certain when a pot decides to blow.

Forrest Gump is my smarter brother.

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OU812 posted this 28 April 2024

The ceiling on my back porch has silver lead splatter caused by visit from tensile fairy.

 

And in that moment I knew the answer

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RicinYakima posted this 01 February 2020

Weather? We had 50's temperatures and high humidity coming up from the coast today; condensation?

Primer? If you are like me, not likely as I hunt them down so the bulldog doesn't' bite them.

Lifeform? Went to the range today and it was so warm the field mice were out. So there could have been the black widows coming out also.

Gremlins!

 

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Duane Mellenbruch posted this 01 February 2020

If the floor is wood, not too likely to pick up moisture.  If concrete, there might have been some condensation from the concrete.  And you might have tracked something on your shoes into that area as well. 

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BigMan54 posted this 01 February 2020

This is why I load in the Garage, and cast on the Patio.

 

Long time Caster/Reloader, Getting back into it after almost 10yrs. Life Member NRA 40+yrs, Life S.A.S.S. #375. Does this mean a description of me as a fumble-fingered knuckle-draggin' baboon. I also drool in my sleep. I firmly believe that true happiness is a warm gun. Did I mention how much I HATE auto-correct on this blasted tablet.

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