I had a blow up even with level 3 alchemy (and level 3 of everything). Everything was finished and I was watching my villagers just for fun. I noticed a little decrease in one of my elderlies health bar, so decided to prepare a health potion. I even picked up my villager ready to use the potion as soon as it finishes. The pot exploded, and some 30 villagers working in the lab began to run away with horror. Gee, it was fun to watch that.