View Full Version : Purple color on top of lead in casting pot?
November 5, 2010, 04:24 PM
Just processed my first load of wheel weights, got 63 lbs. of nice ingots out of 1/2 of a bucket. in the past have used raw lead and added antimony alloy and tin.
The WW alloy has a purple/violet sheen on top of the casting lead when it's hot. Does this mean I'm casting too hot, or is it just a chemical condition common to the wheel weights components?
Thanks, Steve W.
November 5, 2010, 07:08 PM
i usually see blueish purple to gold colors on pure lead melts .
Are these stik on or clip ons???
I can remember a time when ya could`nt scratch WWalloy with ya fangernail!!
November 5, 2010, 07:44 PM
Had some odd coloring during my last smelting session too, found out the pot was too hot. Lee pot @ 6.5, thermometer read much hotter. Hope I didn't miss any zinc weights. :eek:
November 6, 2010, 06:36 AM
They were all clip-ons. I don't have a thermometer, but for years have run the Lee pot at 7.5 with good results. What would be the effect of zinc in the alloy if I accidentally had some mixed-in?
Also, just measured and weighed some bullets cast from this batch.
45 acp's are measuring .451 at drive band, 38 specials at .357+-1 at drive band. All weigh-out within 1 grain of target weight.
November 6, 2010, 08:37 AM
I always thought it was just crap stuck to the WWs. After fluxing and skimming mine seems to go away.
November 6, 2010, 08:45 AM
IIRC correctly the melt won't fill the mould correctly if there's zinc in the melt. Haven't had the problem yet, trying to avoid it. I tried to keep my pot temp low when smelting so that if I missed them they wouldn't melt. Temp went over 900 recently on a full pot with a 6.5 setting. :eek: Zinc weights are usually marked "Zn", only found one in 20+ #'s of WW's. Only found a few in 60+ #'s from an earlier bucket but I was expecting at least one more.
Will cast a few today, strictly in the interests of quality control, of course! ;)
November 6, 2010, 08:58 AM
Color is surface oxides and the temperature affects what color you get. Keep it well enough fluxed and they oxides don't form. Also, lots of temperature controls, the Lee in particular, are linked rather indirectly to the pot, so it is normal for them to overshoot the setpoint initially, then settle down to the control temperature.
Zinc, if it actually get alloyed with your lead, increases the surface tension of the melt, causing it to tend to bead up. This prevents it from filling the details of the mold sharply and can make it impossible to get consistent weight or even full diameter. If you're not having that problem, you don't have zinc.
I'm guessing from your measuring results that you are using a caliper to make your measurements. It's not uncommon for calipers to be off by a thousandth. To be accurate enough for bullets you need a thimble micrometer. Here's one for under $20 (http://www.use-enco.com/CGI/INSRIT?PMAKA=600-0011&PARTPG=INSRCM). It uses a Vernier scale to resolve ten thousandths, so you'll want to learn how (http://biology.clc.uc.edu/Fankhauser/Labs/Anatomy_&_Physiology/A&P203/Circulatory_System/Vernier_scale/Vernier_Scales.htm) to use that if you aren't familiar with them.
November 6, 2010, 09:20 AM
Thanks, Unclenick. Glad you dropped by. I was hoping for a better answer for the OP but couldn't come up with it.
November 6, 2010, 09:24 AM
Those are impurities, metals other than lead and lighter that come to the surface. You must stir frequently and skim those impurities off just as frequently.
I cast only 'pure' lead. But the term 'pure' is not completely accurate. There will always be a small percentage of impurities but I do try to reduce them by frequent stirring and skimming.
November 6, 2010, 09:32 AM
Alright, sounds good guys, I learn a LOT on this forum. And yes, Uncle Nic, I am measuring with a stainless dial caliper, I'll get a micrometer, and I am old enough to understand a vernier scale, heck, where's my sliderule!?!
Thanks a lot guys, Steve W.
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