This is a continuation of my previous post regarding zinc contaminated lead. I disposed of the contaminated lead and made a new batch consisting of lead pipe, some dental x-ray lead foil and tin , (30-1). I also thoroughly cleaned the ladle and fluxed it considerably. 
I continue to have problems. I am using an aluminum double cavity 38-55 mold and getting frosted and rounded unfilled edges on the bullet bands. I have tried faster and slower lead delivery, a bigger ladle, a longer hold on the ladle, higher and lower lead temps (750-950 degreed) and nothing works. Any ideas?
Thanks!
Joe S

You are too hot. Turn the pot off and continue casting. When you get good bullets you will know at what temperature to operate. Then cast at that temperature.

I agree with SM. Cleanup after contamination is very important. You must be thorough. I had zinc contaminated lead and I did not clean up well enough after I dumped that first batch. I thought that a little bit of the zinc infested alloy would do no harm. I was wrong. No matter how small the amount of zinc the bullets will frost and be misshapen and the sprues will break off rather then get sheared off. I never used scrap lead again after that. I found that it was poor economy having to throw away basically 40 pounds of alloy because of the unintentional zinc contamination. (My contamination was from some scrap lead from a leaded glass window.)
Life is so much easier when starting out with known alloy and not needing to do the guessing and cleaning always required when using scrap. Just my opinion from my experience.

My contamination was from those stick on wheel weights when they first started using them.  They had zinc for some reason.  The clip ons did not.

I preheat my aluminum molds on an electric hotplate at Medium while my 1 to 20 lead heats to 710-720. I use a Lyman ladle and hold it on the mold for a count of 3. I put the mold down and pick up a second one which I empty and refill before returning to the first. I cast with 2 molds in rotation so the sprues are solid and the molds do not get overheated. The bullets come out perfect.

I feel for you being on the path of total frustration and often times it just does not pay to try and save money by using what you have. I would also encourage you to try buying your pre-alloyed lead and tin from RotoMetals. Not only do they cover the freight beyond a 99.00 dollar purchase. They also support our sport of Schuetzen and just recently for our May ISSA Regional event they not only freely donated 30lbs. of alloy they also sent several hats and t-shirts for our post match prize drawing. 

JLouis

I was referring to my use of an aluminum mold. As a matter of fact after writing the first post I fired up my pot outside (gas pot) and cast for 55 minutes with a Lee (aluminum) dual cavity 44-40 mold (210 grains) and a Lyman (iron) dual cavity 311316 mold. The yield was 288 bullets (144 from each). Preheating both molds on a hotplate the first bullets from each were good to go and maintaining an even pace both molds stayed at desirable temps. Please excuse the quality of the photo.

Many years ago I encountered a situation where a metallic bluish color appeared in the melt and I could not get rid of it and could not make good bullets with it. I was using wheel weights at the time.
Earlier this year, I put an ingot in the melt and got some of that same metallic bluish color in the melt and could not believe it was zinc because I was confident the ingots were pure lead. However, since then I have not been able to get good bullets, even though I have discarded the entire pot of lead (30lbs) , and tried to start over. 
I melted down hundreds if not thousands of pounds of lead pipe over the years and made ingots, mainly to reduce the storage space. I marked the lead pipe ingots "PB" for lead. I also melted down several hundred pounds of Wheel weights and marked them "WW". It is possible that a contaminated Wheel weight ingot got in the "pure lead" pile and got thrown in the pot.  I have tried to discard any zinc wheel weight but its easy to miss one. I use WW exclusively for .308, 30-06 and 8mm bullets in a smaller pot, so if I get some contamination, I am only out about 20 lbs of lead instead of 30. I use the 30 lb pot exclusively for Schuetzen bullets. 
I believe its zinc because I am not aware of any other reason I cannot get good bullets. I believe others have reported this bluish color that is associated with bad alloy. I have not had it tested.
Joe S