Got a new aluminium mold fom Accurate Molds. After about a hundred bullets with cold laps on the side of the bullets soaked the mold in acetone. That didn't work. Vented the top edges. That didn't work. Warshed it in hot water and dish soap using a scrub brush and gave it a  thorough warshing. That didn't work. Opened up the sprue plate hole. That didn't work. Smoked the cavity with Acetylene soot. That worked. Casts perfect bullets now. 

Why?   

nuclearcricket wrote yesterday at 9:42am:


Ditto. It got to the point where I scooted past all the mold prep, scrubbing, etc. and went straight to the soot in a new aluminum mold, and all is now right in my world.

Soot in a jar or from a lighter or a candle - soot yourself.

I have read, and don't know how much truth there is to it but I have seen it said that soot from candles can leave a bit of an oily film on your molds and that can prevent it from making good bullets. Better to use a butane lighter to smoke them with. 
YMMV
Sam

I bought a 150gr 30 cal double Accurate mold and it still won't cast a bullet without wrinkles. I tried all the aforementioned methods to clean it to no avail. I used candle soot and oxy soot but neither helped. My alloy was 20 to one and my temp was good so I just stopped trying to use it.



JMH

All of my new to me molds, steel/iron, brass or aluminum, get the same treatment. A couple of rounds of a toothbrush and alcohol and wiped carefully with a dry patch. After that, nothing but hot lead, ever. The new mold is checked for proper sprue plate mold clearance and for mold half tightness. If there is any gap it is taken out by filing any raised edge around the locating pin hole or if the locating pin is not extended enough resetting it.   The molds are preheated on an electric hotplate set on medium for the entire time the lead (mostly 20 to 1 or for a few certain molds, 16 to 1 - nothing but pure lead and tin) is melting to 750 degrees. I spout ladle cast alternating 2 molds as fast as I can pour (holding the spout on the mold for a count of 3 to 5) setting that mold down and picking up the second, cutting the sprue/s and dumping the bullet/s in a half full bucket of water (it's just the way I have always done it), refilling that mold, setting it down and picking up the first and repeat. If there ever was a tendency for a bullet to stick in a half of the mold I would use the Paul Jones method of putting a little upward pressure on one half of the mold while opening it. If you really feel the need to smoke a mold, I would suggest using an old kitchen match for the best soot.