I'm looking for an acid or whatever that will react with plaster of paris that has already set to a solid to dissolve it back into a liquid state. Basically, I want to cast something in a plaster of paris mold, but instead of breaking the plaster mold off I'll "melt" it off. I need to do it in this unorthodox way because what I'm going to cast is fragile and a very complex shape that I doubt I could remove from the mold intact any other way. I've read that citric acid can dissolve it, but this was in reference to cleaning small amounts of it off tools, not dissolving a solid mold that weighs ten or more pounds. The acid (or whatever) needs to be fairly cheap and not horribly toxic (no gas mask and thick rubber gloves needed), if possible.