First of all: the problem is not caused by the design, material or manufacture of the mold. The mold is absolutely perfect as received & I'm so happy that I woke up & realized it was available in a group buy. The mold in question is the 8 cavity 9mm 359-130. It is a mirror image of the Speer Gold Dot 124 gr. that is my carry round which makes me feel good about practicing with something similar.
Trial of the new mold was delayed by yard work & cleanup from "Michael". That cleanup is not finished, but I had to take a break & try that mold.
Break-in took longer than expected.....It took me a while to get accustomed to the holes in the sprue plate being close together & I had some spillovers into the next hole. But after a while it began dropping beautiful boolits (over 800).
I cast on the tail gate of my truck & when finished I was waiting for everything to cool down when a light rain came up. Everything got slightly wet before I could pull the truck fully into the garage. I carried the boolits into the house in a towel that got wet & left them there overnight. The next day when I got ready to size/lube them I noticed a white deposit on all boolits that looked alkaline. I rinsed them in water & the deposit persisted. I then rinsed them in a mixture: 2 qts. water & 1 cup of white vinegar & this removed the deposit.
I have a habit that I carry over from steel mold use where I store molds with boolits/sprues in the mold. I know this does not apply to aluminum molds, but it's a habit.
Today when I was preparing to cast with that same mold, I 1st. found some boolits in the mold discolored & then found 4 of the 8 cavities discolored and possibly etched. I 1st. used brake cleaner which produced minor improvement. I then used liquid detergent with a vegetable brush that produced marginal improvement. I then prepared a 20% white vinegar solution in water applied with a large Q-tip (I figure if it'd help with the boolits it might help with the mold) & it did little to help. Finally I applied Evaporust with the same type large Q-tip with no results. To be fair Evaporust is intended to be used with a 12 hr. soak, but I was reluctant to risk damaging my mold even though Evaporust is PH neutral.
To be fair I used the mold after all of these attempts & when I cast them "hot" (as in frosty) they look pretty good. As a practical matter they should shoot better that I.
I have a scrap aluminum piece 3"X1.5"X11/32" that I'll experiment with in a 12 hr. Evaporust soak.
Has anyone ever done an aluminum mold soak with Evaporust?
Has anyone experienced a similar deposit on boolits or mold?
Does anyone have any suggestions as to remedy or cause?
Since it's from rain water I figure it must be acid rain, but what do I know.
Images:
#1 discolored boolit
#2 overall view of cavities
#3 close-up view of contaminated cavities
#4 close-up of vent lines (that seem to function OK)