Small cavity forming when pouring ingots

[WickedRex]

Hey all, got a quick question. I’ve been using my Dutch oven over a Turkey fryer to melt a bunch of scrap lead. Most of the lead is scrap Linotype that was taken from a printshop. Most of it has been melts or scrap from remelts but some has been Linotype letters or slug bars. I’m ladle pouring from a cast iron ladle into RCBS and Ohuas ingot molds. I have 5 molds I’m using. 3/4 of a ladle pours one ingot and pour one at a time. I’ve noticed on many of my ingots I’m finding a slight cavity in the side of the ingot. Sometimes more than others. Some none at all. It’s not siecifuc to a mold and just happens randomly. I’ve tried to speed up and slow down my pours and haven’t seen much of a difference. I’d say out of the 20 ingots I pour at a time, 30-50% of them have a variation of this cavity. I let the molds cool after pouring for about 10-15 minutes before dropping them out. What am I doing wrong??

[deltaenterprizes]

It will not hurt anything, I would not worry about it!

[WickedRex]

I figured it wouldn’t but was just curious on some insight on what I could be doing wrong. I was using muffin pans when cleaning the load of pure lead I had and never noticed anything similar. I appreciate you helping put my mind at ease.

[Winger Ed.]

The alloy is probably cooling real quick and doesn't get a good flow out when it hits the side of the mold.
It just shows you're not wasting energy and paying for fuel/heat you don't need to use.

Other times, I've seen a lot of very small dimples on the sides of ingots.
I think it's steam expansion from the humidity in the air.

As said, don't worry about it.

[Bigslug]

Cold ingot mold + alloy that freezes at a lower temperature = voids. Odds are, your 10-15 minute harden time is well more than enough for lino. If you're pouring one ingot at a time into a 4-5 cavity ingot mold, by the time you've filled the 5th one, your first should be ready to dump, and may retain enough heat to get a cleaner result on the next round.

But they're ingots - unless storage space is REALLY critical for you, don't sweat it.

[MrWolf]

Cut your time down even further after pouring. Consider using a damp towel to put ingot molds on. Don't worry about appearances as your gonna melt them again. Have fun.

[jsizemore]

If you wait for the cavity of a bullet mold to get to cold you'll end up with incomplete fillout. Same with an ingot mold. You got to find the sweet spot between too cold and too hot.

[Edward]

I too would not worry other than (WHY) are you making so hard an alloy/bullet ? 20-1 /16-1 for BP (under 1400)and then what bullet/speed are you planning to use , over 2200fps I use an alloy of 50-50 lead /WW and i won't mention faster as I shoot mostly BP and 530 gr @ 700 yds only needs 20-1 @ 1260 fps/Ed

[kevin c]

Divots, not wrinkles? You’re pouring type metal ingots outdoors in cool weather?

The ingot’s exterior solidifies first (faster in cold weather or with a cold mold), taking the shape of the mold when the pour is at its hottest and at its highest greatest volume. Then the metal inside the ingot cools and shrinks, but if the exterior is already mostly rigid and can’t shrink with the interior, the reduced volume in the metal may form a hole or divot.

I think divots might be more frequent and bigger with an eutectic alloy like linotype, since in cooling between liquid and solid, it doesn’t have a plastic stage that’d let any part of the hardening exterior of the ingot shrink with interior.

But really, other than being careful lowering an ingot with a hole into molten alloy (watch for spatter from trapped air expanding dramatically), the others are right: it’s just cosmetic.

[BRatigan]

When reintroducing those ingots to a melted batch always preheat the ingot to drive away any condensation that will form on the ingot when it's cold. Any cavities are a concern here. I always slowly add my ingots to the pot when refilling hot. The heat absorbed by the ingot should evaporate the moisture before it gets under the surface of the molten lead which then releases the tinsel fairy, who is not your friend.

[dogrunner]

I have told this story before but it bears a repeat as a cautionary note.

Many years back I cast a large batch of ingots....we were in a new home at the time and I hadn't to set up my reloading room and I was substituting an outside screened porch with a picnic bench for a casting table. When finished I stored all those ingots in a cabinet under a pass thru window into the house......but still on the exterior of the structure. Dry spot, but still outside subject to humidity. Must've been Jan or Feb when I decided to cast a batch of bullets and cranked my old Sako up on that table....several ingots went liquid as normal, I introduced several more and went in the house to grab a quick coffe when I heard a loud "whump".............the entire pot was emptied and the cooling contents were solidifying on that bench, where I'd have been sitting and over around three feet of plastic screening!

I have no doubt that coffee habit of mine saved me from serious injury or even blindness given the volume and spray characteristics of that explosion. All I can surmise is that one of the last ingots introduced to that pot had a large cavity internally and it blew.......dramatically!

The ingots were dry as a bone, weather as I recall was drizzly and damp. And no, no water go into that pot. That event is about 40 years in the past, but to this day any ingot introduction results in my temporary absence from the scene

[GregLaROCHE]

I made an ingot mold out of angle iron. It was a lot thinner than I wanted, but was what I had available. After using it I was glad it was thin because I think the ingots cool much faster. That’s maybe why muffins tins etc. work so well. Thin walls won’t cool the lead as fast either. Pouring when the lead is hotter will probably help.