My lead/pewter alloy is a pain to cast with

[Neverhome]

I live in an area with what seems like a thrift store on every corner and pewter goods seem plentiful. Not always cheap but plentiful. So I've stocked up. Most of my current supply of "pure" lead is from plumbing pipes my neighbor donated to the cause.

The problem I'm having is an incredibly high cull rate with this alloy in every mold I've tried. Today I was off so spent some time confirming it's the alloy. Well I THINK it is anyway. The alloy btw is very roughly 1 pound pewter to 9 pounds pure lead. The alloy calculator puts this at roughly 90% lead, 9.25% tin, 0.6% antimony, and 0.15% copper. And yes I'm aware that that is based on HUGE assumptions about the actual makeup of the pewter pieces I've used. Measured density of the alloy is around 10.97.

On the UP side, this expands BEAUTIFULLY and holds its weight very well.

BTW I confirmed it's the alloy that is the problem by casting using two other alloys and they worked as expected. Shoot one of them wasn't an alloy at all! I used straight lead and it filled out better than the pewter alloy.

So what's the deal? Did I screw up and mix something else into my pewter? Any other possibilities?

[brewer12345]

Why not have bne do an xrf test for you?

[Time Killer]

a few picks of the bullets would help. But it sounds like you may have something in the alloy that is causing this condition. I would recommend the same as brewer have bne test it for you.

[MyFlatline]

I have found that when you have copper in the mix you need to run the pot hotter to get good fill out. I personally try to add copper. I feel it makes the bullets "tougher" not necessarily harder.

I run my pot at about 750° and have good fill when to mold is to temp.

[Neverhome]

a few picks of the bullets would help. But it sounds like you may have something in the alloy that is causing this condition. I would recommend the same as brewer have bne test it for you.

Wish I had some the culls but of course they just get tossed back in. There was nothing really striking about the flaws. Pretty standard lack of fill out. Mostly noses and bases with some random gaps and wrinkles.

I'll have to look into a test. Hate to trash my pewter if it's something else.

[Neverhome]

I have found that when you have copper in the mix you need to run the pot hotter to get good fill out. I personally try to add copper. I feel it makes the bullets "tougher" not necessarily harder.

I run my pot at about 750° and have good fill when to mold is to temp.

I do have to run the pot very hot to get rid of the above mentioned flaws. Well, to reduce them anyway.
I don't have a thermometer but I have to run this alloy to the point where it is oxidizing rapidly. Much more than I'd like

[RogerDat]

bne for the real info on what you are casting with. Send him a pea sized drip and a pound of any lead and he will test the drip. Hotter pot to see what that does. You probably aren't too hot unless you have frosty bullets.

It is possible one of those pewter pieces had zinc plating or zinc handles. Low percentage of zinc won't oatmeal up on you but it will pour funky into a mold. Hotter helps with that. I know this because I have a small bin of pewter with zinc contamination. Even though almost 90% tin and only a few percent zinc it can only be used in small amounts with larger batches. Have to get the zinc down below about 2% and run hot but it does make some pretty hard bullets Was thinking of using it for buck shot.

[redhawk0]

Are you 100% sure you have real pewter? I've seen so much "pewterete", "armalite" and the **** from Wilton (Columbia PA) that if you got some of that you may have undesireables in your Pewter melt.

You should have good fill out with 3% or less of Tin.

Just throwing it out there as a possibility...you might want to have BNE test it as suggested just for peace of mind.

[EDIT] I guess the word [rap is banned...but i see the word crappy isn't...go figure....gotta love the inconsistency of forum police.

redhawk

[MyFlatline]

You should really invest in a good thermometer, I don't always use mine but have been able to establish a good mark..

The fact that you can cast pure lead perfectly , leads me to think you are still to cool on the pot. Hopefully someone with more brains than me chimes in. Best of luck

[bangerjim]

I agree with the others. TEST IT!

You could have something besides just pewter in those "things" you melted down. 2-3% Sn is all you need.

A little Cu does not hurt. I have several mixes I do that have ~1% Cu and they behave just like COWW's when cast in a PREHTEATED mold. You ARE preheating your molds to full casting temp on an electric hotplate, right? That gives me (and most others) perfect drops from the 1st pour.

Let us know what the test results are.

bangerjim

[Grmps]

When smelting the pure lead, what did you flux it with and how many times?
in smelting the pewter what did you flux it with and how many times?, did you keep the temperature under 600° This rules out non-pewter/tin alloys
Pewter is apr 90% tin 10%lead. you may need to add more pewter to get 10 to 1

If you plan on doing any amount of casting (and you can afford it) you may want to look into building or buying a PID controller for you casting pot.

[Neverhome]

You should really invest in a good thermometer, I don't always use mine but have been able to establish a good mark..

The fact that you can cast pure lead perfectly , leads me to think you are still to cool on the pot. Hopefully someone with more brains than me chimes in. Best of luck

No. Definitely not too cool on the pot and definitely not too cool on the mold. Like I mentioned I have to run the alloy way hotter than I like. I should have elaborated that other alloys don't need to run this hot.

You are obviously correct. I do need a thermometer. I typically establish my best temp VERY imperfectly based on mold fillout and oxidation rate. It's lazy and I really should just spend the 40 bucks.

[Neverhome]

I agree with the others. TEST IT!

You could have something besides just pewter in those "things" you melted down. 2-3% Sn is all you need.

A little Cu does not hurt. I have several mixes I do that have ~1% Cu and they behave just like COWW's when cast in a PREHTEATED mold. You ARE preheating your molds to full casting temp on an electric hotplate, right? That gives me (and most others) perfect drops from the 1st pour.

Let us know what the test results are.

bangerjim

Yup. Hot plate in full effect. And yes the lack of good pours is EXACTLY why I asked the question!

[Neverhome]

When smelting the pure lead, what did you flux it with and how many times?
in smelting the pewter what did you flux it with and how many times?, did you keep the temperature under 600° This rules out non-pewter/tin alloys
Pewter is apr 90% tin 10%lead. you may need to add more pewter to get 10 to 1

If you plan on doing any amount of casting (and you can afford it) you may want to look into building or buying a PID controller for you casting pot.

Good questions that I have NO answer for! I smelted this lead and this pewter months ago. But in general I use a wooden paint stick and stir and burn as much as needed for the melt to not apparently have any impurities. The problem though which has been made obvious is that my cheap butt doesn't own a thermometer so I have no idea if I'm going above the temp where I'd be melting anything bad. Just lazy and cheap on my part. I'll remedy that asap!

[daloper]

You might want to update your profile to include your home state at least. Possible that you might be near someone that could give you one on one help. Maybe I am wrong but 9% tin seams to be high and a waste of tin. I try to keep at around equal pure lead to CWW with just enough to help the pour. Like already said have you melt tested.

[Neverhome]

You might want to update your profile to include your home state at least. Possible that you might be near someone that could give you one on one help. Maybe I am wrong but 9% tin seams to be high and a waste of tin. I try to keep at around equal pure lead to CWW with just enough to help the pour. Like already said have you melt tested.

I was shooting for a predicted 12 bhn with this alloy. It was supposed to be for the most part like 10:1 alloy.
Interestingly, it should have been about the same bhn as the other main alloy I use which is 50/50 Lyman#2/Lead. Well, the pewter/lead alloy is actually quite a bit harder.

[Neverhome]

So hypothetically, how would zinc in a bullet act when fired in to a medium? Would it be likely to shatter like too much antimony or would the large amount of tin I'm running mitigate that?
I'm not saying that's what my problem is, I'm asking because I've shot a great deal of this alloy into duct seal for...um...science

[bangerjim]

If you think your “pewter” has Zn in it.....do the acid test. HCl driipped on it will react with bubbles and frothing. Even a few % Zn will show bubbles in a short time. Pure Zn will react violently and bubble up.

HCl (pool acid) is avaialble at any pool store for pH adjustment. H2SO4 (battery acid) is much lower in hydrogen ionic strength and will not work learly as well, so don’t bother.

Just one solid way you can test what you have for Zn contamination.


Zn is lighter than Pb and will make your boolits under weight quite a bit. And it is harder also. You can cast boolits out of pure Zn if you get the mold and melt hot enough.

Bangerjim

[redhawk0]

I was shooting for a predicted 12 bhn with this alloy. It was supposed to be for the most part like 10:1 alloy.
Interestingly, it should have been about the same bhn as the other main alloy I use which is 50/50 Lyman#2/Lead. Well, the pewter/lead alloy is actually quite a bit harder.

Yeah...you definitely have something else in there. Tin by itself doesn't add much hardness to the alloy. The harness comes from the Antimony. If you are mixing 50/50 Lyman#2 and pure lead then you're about 2.5% Tin and 2.5% Antimony which is just about perfect....I shoot for 3% and 3% when I'm mixing....but as already said...1-3% is enough for tin. Maybe some Silver or even Cadmium is in your Pewter...again...it might be worth testing so you know for sure. Just a little bad stuff could make it impossible to alloy with.

redhawk

[Neverhome]

If you think your “pewter” has Zn in it.....do the acid test. HCl driipped on it will react with bubbles and frothing. Even a few % Zn will show bubbles in a short time. Pure Zn will react violently and bubble up.

HCl (pool acid) is avaialble at any pool store for pH adjustment. H2SO4 (battery acid) is much lower in hydrogen ionic strength and will not work learly as well, so don’t bother.

Just one solid way you can test what you have for Zn contamination.


Zn is lighter than Pb and will make your boolits under weight quite a bit. And it is harder also. You can cast boolits out of pure Zn if you get the mold and melt hot enough.

Bangerjim

Interesting! Thanks for the tip.
Most metals will react with strong acids. Meaning tin and antimony should as well. Is zinc so reactive that there would be no confusing its reaction for one with tin and antimony?
I remember once upon a time putting chunks of zinc into a vial of HCL and collecting the hydrogen gas that was released. Then we'd ignite the hydrogen. Good fun in chemistry class