Douglas, thanks!
I'm doing tests now to get it to work better without scrapping a whole 2 day print.
I thought you were the one that originally said to use sand as an aggregate? Maybe not.
The current recipe I'm working with is variations on plaster/drywall compound, sand, mortar, water and a drop of dish soap. Supposedly the dish soap causes the bubbles to stay smaller almost like creating a ceramic foam, apparently that is a big part of what makes the commercial stuff different from just regular plaster.
I'm thinking that the biggest issue right now is the oven inconsistent and getting too hot. That one I posted, stayed intact for almost an entire day until I turned the heat up. The oven was outside at -10.
I poured plaster samples this weekend but I need to finish the mods to the oven.