Unless your terminology is wrong, it sounds like you might be approaching your mold the wrong way. Number one, I would recommend using a cement, like Ultracal 30, or a stone, like Dental Stone. Number two, multiple coats without something strong like burlap to reinforce them, is useless and just add weight. does not mater how thick an unreinforced mold is, it can still crack in half easily. Number 3, each new addition to the mold should be applied before the previous layer has started its curing heat cycle. Any deviation from these methods leads to a mold that can easily break.