dave_j wrote on Jun 22^nd, 2017 at 9:33pm:


Put some chlorine bleach in some water.  Put the alloy in and watch for small bubbles.  The stronger the mix, the faster the bubbles. 

Some may be just occasional, be patient and watch for two or three minutes.

I hope you are correct about the blue not being a zinc problem, but every time I have had a problem I have had the blue color. an association, not necessarily a cause and effect. Will try the bleach and see what happens. At any rate, blue or no blue, I still need bullets to shoot. 
Thanks for your help, will keep working on it. New mold, pot and certified alloy is in the mail.
Joe S

IME, the blue color is the indication of high heat in an alloy that is mostly lead.  I get the blue "skin" on top,of the alloy when casting round balls for muzzleloaders and the like.  The silvery balls will turn blue as they sit on the towel, cooling off, if I'm running the pot hot enough.

The only time I had zinc contamination, the contents of the pot was an uncastable slush, like silver oatmeal, that refused to liquefy at any normal casting temperature.

Lead reacts slowly with muriatic (hydrochloric) acid at room temperature, giving off an occasional bubble and forming a white sediment that will dissolve if you heat the solution up.  Zinc reacts rapidly with the acid, giving an "Alka-Seltzer" fizzing reaction, and the product dissolves in the acid solution as fast as it is formed.

You would need to try pure lead and pure zinc with the reagent and judge for yourself the level of zinc contamination by the extent of reaction of a mixture of the two.

Check the venting on the blocks adjacent to your "trouble spot" on the bullets.  If it looks good and the problem is at the base, sometimes a slight loosening of the sprue plate will help.

If everything looks OK mechanically, smoke the mould with a match or a candle, or spray cavities, faces and tops with Mould Prep or some other similar stuff.  I know it's wrong; it's shameful; it doesn't address the true problem with the mould, and it reduces bullet diameter by a squillionth of an inch, but I do it on all my aluminum moulds and get an avalanche of good bullets when I do.

Alloy was 20:1, pot temp about 720-730dF.

Technique was to fill, continue to fill leaving a quarter-sized puddle above each cavity, cut the sprues just after the puddle froze, and to drop bullets onto towel.

300 gr bullets, so the flow was adjusted to be large.

The solution.  Empty the pot and clean the nozzle from the inside.

Note the difference in flow from the stream accumulating crud - as it flowed - going from robust to wimpy.   

Cleaned it out, fired it back up and cast 250+ GOOD bullets.

thanks for the info on the bleach   will try it   the melt makes good bullets so i have not worried about that    thanks again   dave j