Pure Lead? Please confirm

[romukom]

I am slowly trying to learn about bullet casting. I was able to get 180 # of lead from a scrap yard. It came on a 12x24 x 2.5 block (380#). I took half and the other half they will save it for me (pastry and coffee really helps :) ) I just smelted a chunk into smaller cups. Based on the pencil test I do have pure lead.
-Can you confirm that?
-If is pure lead, is that normal they way it shrunk? I had some wheel weight done and did shrunk like that.

The one on the left was poured after fluxing with saw dust. As soon as I scooped the second pour, I started noticed this yellow then bluish film on top. I was trying to skim it off but it continue to form. So, I decided to keep pouring and not waste fuel since I was running low.
Thanks.

https://lh3.googleusercontent.com/-VX-8OucjN88/VxFvndOOLJI/AAAAAAAAAls/L09co2F8iSw5xgt1hlm0-P3E_s31pTcvQCCo/s640-Ic42/IMG_3907.JPG


https://lh3.googleusercontent.com/-Hgwkg_6cQLk/VxFvnSq09PI/AAAAAAAAAls/Zxk-Ey3X4wgdXjP-FeBejGHqVosHtRIpwCCo/s640-Ic42/IMG_3908.JPG

[romukom]

Oh I just found my answer. Indeed this is pure lead.
http://castboolits.gunloads.com/showthread.php?304810-What-caused-this

[Budzilla 19]

That's what mine look like when poured out. Don't know why it does that. I bet we'll hear the answer though.

[Ballistics in Scotland]

From the description in the other thread it sounds like pure lead. Another way is to suspend a piece of it from a scale, and weigh it both dry and when suspended in water. The dry weight divided by the difference between those two weights is the specific gravity, i.e. the number of times the alloy is heavier than water.

With pure lead it should be about 11.34. All metals currently used to alloy it are lighter (though in the past big-game hunters sometimes, in blissful or unblissful ignorance, hardened it with mercury, SG 13.6). So if it has a specific gravity less than 11.34, it is less than pure.

[romukom]

Interesting way to find the material using the specific gravity. I should have paid more attention at school :)

I just found this information in the Los Angeles Silhouette Club website (I need to read more). If you read the last sentence it makes sense. I got near pure lead, and round cupcake size ingots.

http://www.lasc.us/CastBulletNotes.htm








Alloy shrinkage of cast bullets







Composition, %

Brinell

Shrinkage










Type Metal

Tin
Antimony
Lead
Hardness
Linear, %










Linotype
4
12
84
18
.65


Monotype
9
19
72
26
.65


Lead
--
--
100
5
1.13


Tin
100
--
--
7
.90


Antimony
--
100
--
50
.47





As an example: the solidification of a nominally .357" diameter bullet cast of Linotype could be expected from the above table to be .0065 X .357" = .0025". In a soft alloy of lead and tin, .01 X .357" = .0035".
















Shrinkage - Bullet Diameter, Inches





Alloy
.308
.357
.452


Linotype
.002
.0025
.003


Lyman # 2
.0025
.0025
.0035


Soft Lead
.0035
.004
.005









From the above two tables it can be seen that the softer the alloy and the larger diameter the bullet that more shrinkage will occur.

[Ballistics in Scotland]

Interesting way to find the material using the specific gravity.

Well, up to a point. If you know there is only lead and one other identified metal, you could calculate the composition very accurately. But how often do we? If there are two or more metals besides lead (most often tin and antimony), all you can say is how close to pure lead it is.

[runfiverun]

it gives you a clue though.
if the amount of other is near 4% and my tester said 10bhn, I'd be super comfortable calling it ww alloy.

I'd let it sit for a week and the guesstimate bhn test again if it comes out near 5 again I'd say you got lead there and it's clean lead.