Lead Deposits in Aluminum Mold

So, I have been running into a problem with all of my aluminum molds. I am getting lead deposits on the mold face while casting. Some times they will wipe off with a dry rag when the mold is up to casting temperature but most of the time they will not. The deposits get built up enough that it allows me to see light between the mold blocks when they are closed. I am casting at around 720 degrees with a soft lead with tin combination. I do not add sprues back to the pot as I am casting. I am really trying to figure out a way to first figure out what is causing this issue and then a way to clean the offending material off of my mold faces. It's really disheartening to have a brand new NOE mold be disfigured by this issue. I've attached pictures of the issue in question. Any held would be much appreciated. Thank you.

Squeeze the handles a bit tighter when you cast?

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Originally Posted by imashooter2

Squeeze the handles a bit tighter when you cast?

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Is that a thing? I could see that on one mold but it's happening on several of them. Even my molds from NOE that don't let light shine through the mold faces with minimal pressure. I'll try it next time. I don't limp wrist when I'm casting but I'm not bowing up on them either.

Doesn't matter the mold maker, all molds I use take a bit of extra attention to make sure the mold halves are fully seated closed. I give the handle joint (never the mold itself) a little tap-tap as I squeeze closed to make sure the halves have fully seated. You don't want to squeeze the handles real hard; just get a little vibration in there when closing to make sure they are seated fully.

Coloring the faces with a pencil will stop the buildup. Clean the specks off, color it real well when cool. If anything appears when casting, take your pencil and poke at the speck and it will fall right off. Works amazing for smears between the sprue cutter and blocks too. Graphite is a dry lube so no need to use oil. I remove the sprue cutter and color the whole block top and cutter bottom and screw. Don't forget the alignment pins.

I've cast A LOT of boolits, the only times I get spots like that is when I see boolits with bad bases and drop the boolits directly back into the pot and get splatters. (now I just drop them on the corner of the towel I use and put them with the sprues.

That looks like a splatter of some sort from somewhere. I would re-visit your casting procedure.

How do you cast?

for cleaning, I use bamboo skewers and with the mold hot the specks should come right off. Some use a lead ingot to rub the speck off. Being aluminum don't use metal items to remove the speck if needed you can use a propane torch and heat the whole mold half EVENLY to soften the lead specks

I am in the camp with coating the mold with graphite from a pencil and checking alignment.

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Originally Posted by Conditor22

I've cast A LOT of boolits, the only times I get spots like that is when I see boolits with bad bases and drop the boolits directly back into the pot and get splatters. (now I just drop them on the corner of the towel I use and put them with the sprues.

That looks like a splatter of some sort from somewhere. I would re-visit your casting procedure.

How do you cast?

for cleaning, I use bamboo skewers and with the mold hot the specks should come right off. Some use a lead ingot to rub the speck off. Being aluminum don't use metal items to remove the speck if needed you can use a propane torch and heat the whole mold half EVENLY to soften the lead specks

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I drop sprues into a separate pot that is added back in all at once. I don't have a shelf for the mold to rest on underneath the bottom pour Lyman pot. If the mold isn't level could that somehow be forcing the lead in between the mold faces? Its really frustrating and this lead is STUCK on. I've been heating and scraping with wood chopsticks and Kroil soaking overnight. Still not all the way gone.

This usually comes from opening the mold too soon. The bullets are still a bit wet.
The lead will always wipe off easily if the block is hot enough and you are quick enough.
Next time you cast with this one, cast at a brisk pace until hot. Sprue takes about 8 seconds to dry.
Then QUICKLY wipe off the lead with a small rag or Q tip.

You will learn to recognize when you opened early. Bullets a bit too shiny wet.
Keep the rag handy and be quick.

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Originally Posted by TomAM

This usually comes from opening the mold too soon. The bullets are still a bit wet.
The lead will always wipe off easily if the block is hot enough and you are quick enough.
Next time you cast with this one, cast at a brisk pace until hot. Sprue takes about 8 seconds to dry.
Then QUICKLY wipe off the lead with a small rag or Q tip.

You will learn to recognize when you opened early. Bullets a bit too shiny wet.
Keep the rag handy and be quick.

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That makes a huge amount of sense. I will try waiting longer to open the mold. The location of the deposits makes this theory seem likely. I’ll try and make a report back on this thread after my next casting session. Thank you.


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Watch for the sprue to change colors.

Interesting, I've never gotten wet boolit splatter. that's a new one to add to my grey matter.

For a big mould like that the toggle-clamp handles that Buffalo Arms sell would help a lot. I bought a set a few years ago, because of my arthritis. The uniformity with which the mould blocks are held closed improved all of my casting, even little .22s.

https://www.buffaloarms.com/aluminum...les-ctaluminum

It's hard to slow down when the bullets are raining, but more than likely that's what you have going on here. As was posted earlier, get it hot and wipe it off if possible. If it's still stubborn, get it hot and use a carpenters pencil and scrape it off. Been there before myself and I've come to the obvious conclusion that it was my fault for going too fast and hot.

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Originally Posted by LakeviewBulldog

Is that a thing? I could see that on one mold but it's happening on several of them. Even my molds from NOE that don't let light shine through the mold faces with minimal pressure. I'll try it next time. I don't limp wrist when I'm casting but I'm not bowing up on them either.

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Yep, it's a thing. You could also be squeezing too tight. Don't just hold the blocks together, get the mold hot and squeeze it as tight as you normally would, eyeball it for light between the blocks.

My Lee .358-158 2 cavity mold gave me trouble with lead deposits. Don't know exactly why, because I had been casting for a couple of days with zero issues. I remedied the problem by opening the sprue plate as far as possible, and the dunked the whole thing into the molten lead in the casting pot. Did that a couple of times and the mold came out clean.

To the OP: is your lead clean?

Does the pot valve get clogged?