Alloy problem I think..

[Grandpas50AE]

I recently smelted down and made ingots with the remainder of a bucket of WW (about 1/3 of a 5-gallon bucket I got 5 or 6 years ago). I started using these ingots with about 15% pure lead and 2% tin added, and noticed a "sink hole" in the middle of the alloy when it cooled back down. I could see in the hole and noticed a lot of crystaline appearance. Saturday I added some more pure lead and a little more tin and cast some very nice boolits in one of my new MP molds. I thought I had the alloy adjusted, but yesterday I cast some more out of the other MP mold (H&G #68 clone), and had a fair number of rejects due to part of the front drive band looking like it had sheared off sometime after dropping from the mold. It is possible the band didn't fill out properly to start with, that I am not sure of. At any rate, after I turned the pot off for the day, I inspected it again after it cooled, and sure enough the "sink hole" was back. It wasn't there when I shut down Saturday evening, so I thought I had the alloy problem figured out.

I had this happen many years ago and just figured it was extra antimony and added lead back, but it seems to be taking a lot more lead to act more normal. Is this an indicator of high antimony, or perhaps a different metal in the WW material that is not easily handled by just adding back extra lead and tin?

[runfiverun]

it's the cooling effect.
it will happen to boolits that don't have lead to draw from a sprue.
your pot cooling quickly will make that dimple or hole larger.
look at your sprue while casting you will see that same dimple form.

[stubshaft]

Make sure you pour a larger sprue puddle too.

[1Shirt]

Better to much sprue puddle than little or none as suggested. Also suggest bullplate.
1Shirt!

[captaint]

The appearance of the lead in your pot, when cooled is quite normal - in my pot also, anyhow. enjoy Mike

[MT Gianni]

I have a mold I continue to pour alloy over for 10-15 seconds after it is filled. THat is the only way I get good base fillout with it. It shoots so well I find it worthwhile.

[Grandpas50AE]

When the alloy completely cools, the surface area has a sparkly appearance near the sink hole, kind of like the appearance of diamond particles. Is this indicative of some contaminate material in the alloy, and if so, how to get it out? I'm using sawdust for a flux when casting, and Marvelux when smelting ingots.

[btroj]

Sounds like a hot, hot, hot mould and an extreme frosting.
How hot are you running the melt and mould? How long does it take the sprue to harden?
I find the only time I get that extreme graininess is when my mould is too hot.

[Grandpas50AE]

Sounds like a hot, hot, hot mould and an extreme frosting.
How hot are you running the melt and mould? How long does it take the sprue to harden?
I find the only time I get that extreme graininess is when my mould is too hot.

According to my thermometer the alloy temp is 690*F to 700*F. The sprues (fairly generous puddles) take approximately 5 - 6 seconds to solidify. I keep my mould cadence at approximately 3 pours per minute, and the sprue solidification stays right at 5 - 6 seconds, then push sprue plate open with gloved hand.

[btroj]

Looking back at your original post I see you have some with the front band breaking of when dropping from the mould. That, along with the long time for the sprue to harden tells me it is likely an overly hot mould. Either don't preheat the mould quite so hot, if you are preheating it, and slow down your rhythm a bit. I like my sprue to harden in about 3 to 4 seconds.
You could also probably cut the mystery lead with pure about 50/50. High Sb alloys are more likely to show the problems you described.

[Grandpas50AE]

Thanks btroj, I will try slowing the cadence a little, as well as cutting the mix with more lead. The hotplate preheating still leaves the first few pours wrinkling, so I don't suspect the preheating of being too hot. Once I pick up the molds and start to cast, I don't set them back on the hotplate until I've emptied the pot and have to stop to refill it.

[popper]

If that's regular WW, you should have a 2% SN, 2.5% Sb alloy(10 WW, 1.5 Pb, .5 Sn). Fluxed with sawdust (not plywood saw dust) mixed good and let sit for a while before casting? I saw crystal spots in CB until I changed to wood shavings, The sawdust I got from the HW store, probably MDF or plywood. my melt and mould temps are about the same as yours, alloy is about the same.

[Grandpas50AE]

Thanks popper, i had just ordered some CFF from Pat Marlin and it should arrive around the end of this week. The sawdust I was using was pretty fine, but from cutting clean pine 2x4's on a recent project. I hadn't made too many cuts, so I ran out of sawdust Sunday towards the end of my casting session. Perhaps the sawdust was too fine and causing it own set of problems, but with the ideas you guys are giving me I'm sure we'll have it worked out pretty quick and my reject rate will be back to what it was when I was casting a lot. Thanks everyone for the ideas and help.

[runfiverun]

i think you are just running the alloy too hot.
mold temp is what controls everything.
waiting a long time for a sprue to cool is the first clue, you should be able to open a sprue while the sprue is still silver.
and have no smearing.

[leadman]

I agree with the temp of the mold too high. You may want to inspect your mold for burrs also.
I have a mold that all of the sudden it started the same thing with the front band. Found a little chunk of lead or something stuck on the bottom edge of the band cavity. Don't know exactly what it was but used a propane torch to melt it off. Could have been some contaminate that was in my alloy. The alloy being too hot will cause this also.

A popsicle stick cut with a knife so there is an angle across the width and then beveled on both sides like a knife blade is great for running over the cavities to check for burrs. Gives good feedback on what the mold surface is like.