Dirty boolits??

[captaint]

Where to begin.... Yesterday afternoon I emptied out and cleaned the ProMelt out. OK, nice and clean. I melted about 16 lbs of 50/50 WW - Pb,l and started casting. I was making 250 gr .375 boolits in a LBT 2 cav mold. Nice mold, by the way.. First, I fluxed the melt really well with sawdust, oak. I cut it myself, so I know it was oak.
Right from the beginning, I'm getting dirty boolits. So dirty, I could see the dirt in my sprues, every pour. Fluxed again. Stir, stir. Let the sawdust burn up and stir again and again. Still dirty boolits. Nasty looking. Threw them back in the pot.

My question is - could my mix really be that bad, or am I doing something wrong. I did flux a couple of times when I smelted the WW's and lead. I'm smelting in a cast iron dutch oven, fairly new. So, how could my mix be that dirty, and why couldn't I flux it out??? Finally I got my ladle (RCBS) and poured that way. Much better. Success, actually. I have heard that bigger boolits are easier to cast with a ladle. Still, why all the dirt. And what do I have to do to get it out??? HELP.!!
enjoy Mike[smilie=b:

[geargnasher]

Is it really dirt or ash trapped under the melt? Or is it that you're running your alloy about a million degrees too hot and burning the tin out on the surface of the pouring stream, where it forms grey, flaky dross clumps on your sprues and the surface of the boolits?

ladle casting, especially if you contact-pour, eliminates SOME of the oxygen exposure and can reduce the appearance of the "dirt".

If you didn't force the sawdust to the bottom or scrape the bottom of the pot with a stick, there isn't much chance the sawdust got trapped on the bottom. It's probably tin.

Keep your pot temperature below 700 degrees and the appearance of that stuff from clean allow will greatly diminish.

Gear

[captaint]

gear - no, I don't run my pot hotter than about half a million degrees. And no, I don't scrape the bottom of the pot with anything. I do stir with a hardwood stick. And no, not clumpy in appearance. More like fine dusty looking. And I was thinking the tin burned off at the top, rather than the bottom. Maybe I'm using too much sawdust.... enjoy Mike

[cbrick]

A clue could be in the first part of your post. I had a similair problem several years back after "cleaning" the RCBS pot. Did you do what I did?


Yesterday afternoon I emptied out and cleaned the ProMelt out. OK, nice and clean.

Explain how you cleaned it and everything you did prior to putting in ingots to melt.

What I had done was use a good stiff wire brush on a drill motor to grind out a large amount of caked on Marvecrap. No wonder I won't allow that #%^$ in my loading room much less my casting pot. When I was finished I dumped out the dust and wiped it out with a rag. Great, good to go.

Well, not to good to go. I couldn't get a good bullet to save my heiny. They looked just like your description and just like you ladle casting did help, some.

The solution, empty the pot and clean it again. No caked on stuff this time, I had gotten rid of the Marvecrap, well, almost. I soakd a clean, white shop rag in denatured alcohol and wiped down the inside of the pot, the rag came out almost black. I repeated with clean rags until they came out clean and then flushed the pot with alcohol. What I did with the first cleaning was leave a lot of the Marvecrap dust in the pot. When the alloy melted all that dust seems to have collected in the alloy near the bottom of the pot.

That was the last time I have ever used Marvecrap, tossed it in the trash and never looked back. I use sawdust only now and have had no problems with dirty alloy in the years since.

After the second cleaning with alcohol I refilled the pot with different ingots and all was well. Later I filled the pot with the dirty ingots, it took many sawdust fluxings but I did finally get most of the crud out of that alloy and did use it up.

So . . . Just how did you clean your pot?

Rick

[captaint]

Rick - To clean the pot, I got some spray cleaner and did it by hand with a "green pad". Then I scraped some junk off and wiped it with a wet paper towel. I felt it with my hand to be sure there wasn't any loose stuff left. Maybe I should have used alcohol. The sides of the pot were not bad, but I was amazed at how much loose "dirt" there was laying in the bottom.
Maybe gear is right. Maybe I baked my tin out.
Question is, if I did burn the tin, now what?? Will it blend back in or do I have to toss the remainder???
Tell you this though, I will empty it again and clean. I hate the thought of tossing lead.
Thanks for the help.. enjoy Mike

[cbrick]

Maybe I'm using too much sawdust .... enjoy Mike

No, the only thing you'll do with too much sawdust is waste the sawdust.


Maybe gear is right. Maybe I baked my tin out. Question is, if I did burn the tin, now what?? Will it blend back in or do I have to toss the remainder???

I hate the thought of tossing lead. Thanks for the help.. enjoy Mike

Tossing lead? Now don't get silly. No need to toss anything (well, Marvecrap if you should have any of that horrid stuff).

At what temp where you casting? Even if you were too hot and did oxidize the tin simply replace the tin if it's needed. If it's still there as oxidation on top of the melt sawdust flux will reduce it back in.

A lack of tin will not make the bullets look like they where cast with dirty alloy. When tin is needed and not in the alloy the result is bullets that are not as sharply filled out as you would like, rounded driving bands etc., not dirty bullets. Dirty bullets come from dirty alloy.

Rick

[captaint]

OK, I get it. I was thinking more along the lines of "if the tin is oxidized, maybe it leaves some dirty residue". I actually always believed when the tin oxidizes, it's just gone... Guess I'm confused about what happends when the tin gets burned up, if that's what happened.
Anyway, I'm gonna empty & clean again, add half a pound of tin and start over. Live and learn.. Looks like this never ends. And that's OK too. enjoy Mike and thanks again.

[BABore]

Your using 50/50 WW-Pb right? Great alloy. Also very low in antimony at 1 1/2 to 2%. You can add all the tin you want to pure lead and never have a problem. You can add too much tin to an alloy with antimony in it. Tin and antimony like each other up to a certain point. Look at the tin/antimony ratios in linotype, monotype, etc. It's about a 3 to 1 ratio of antimony to tin. Your excess tin, in your 50/50 alloy, likes to migrate to the boolit's exterior and drag any junk, dross, dirt, etc. with it. Run no more than 1/2% tin with your 50/50 and the fuglies will go away. Been there, done that.

[captaint]

Thank you BABore - I did have plenty of tin in that 50/50 WW-lead mix. DID have.. I'll have to try fluxing the stuff out. Gonna clean the pot out first, though. Thanks Mike

[runfiverun]

too much tin will leave some goofy looking spots on your boolits in an alloy with antimony.
i think the cleaning is your problem.
try just plain ol boiling water with some citric acid in it.
then the pad again.

[BABore]

Thank you BABore - I did have plenty of tin in that 50/50 WW-lead mix. DID have.. I'll have to try fluxing the stuff out. Gonna clean the pot out first, though. Thanks Mike

Fluxing doesn't automatically remove junk from an alloy. It only allows the oxidized elements to be reconstituted into it. Stirring, scraping, and skimming repeatedly removes the dirt. The boiling action of a wood stick helps float the suspended dust to the top.

When melting WW's down, I flux once when the clips are removed, then a second time after stiring and skimming. It takes me upwards of 20-30 minutes to stir and skim all of the crud from a 100 lb pot of alloy. It may seem like a long time, but time spent there saves alot of fugly boolits with inclusions that create imbalance.

[geargnasher]

Just to clarify, the tin won't "burn out" at the bottom of the pot.

You said the dirty spots were in your sprues and on the boolits, so I offered the following as a possible explanation, see if it makes sense based upon what you're doing:

What happens with alloy that's too hot and/or has too much tin in it (as BABore explained the cause/effect of that), is that the tin on the surface of your pouring stream flash-oxidizes on the surface of the stream, forming dross like you get on top of your pot in an instant. This oxide scum can form clumps on the surface of your boolits that look like dross inclusions. Also, it forms on the surface of your sprues, right in the middle where the pouring stream ended.

Dumping your oxide-infested sprues and boolits back into the pot will bring this dross to the bottom, because the cold, solid lead has a higher SG than the molten lead, and therefore sink. Once on the bottom, they melt in short order, leaving the powdery dross trapped under the surface of the melt due to the high weight and surface tension of the melt. The dross then migrates to the spout as you pour more boolits, creating an endless cycle of dross inclusions.

This is why I don't add sprues or boolits back to the pot as I go anymore, did it for years but the results showed it. I add them back all at once when refilling the pot, and I stir/scrape/flux until I get all the crud worked to the sides of the pot and up to the top. The powdery dross and scum on the bottom will not just float up through the lead, there is too much resistance.

Gear