Hi guy's , thanks to you after a year of research on this site i decided to try my hand at plastics . I 'm using one of Del's 5 in. stick molds, Calhoun plastic, no salt ,no softner .I have poured 250- 300 stik worms with no dent or voids . my first pour I couldn't hit center of the hole for nothing but i'm getting better . My guess would be lack of additives ie, salt , softener . i am now using scent in them as well , but still no dents or voids [not that i want them] . if the plastic does'nt stick to my finger in the pour hole i demold them . Just another angle to look at this dent thing. hope this helps in some way .