Dissolve Plaster of Paris

[ninapilapil]

My groupmates and I were using plaster of paris for our Arch 10 scale model of a chair. We used a glass casserole for the first trial. Kind of stupid. We covered it with oil before putting in the mixture but when the mixture dried, we couldn't get it out anymore. How can I dissolve plaster of paris?

[chemisttree]

Water and time will eventually get it out. Acid or sugar will accelerate it somewhat.

You can convert the dihydrate back to the hemihydrate by baking it at 150F for several, perhaps many, hours. It should then crumble easily.

[ninapilapil]

Water and time will eventually get it out. Acid or sugar will accelerate it somewhat.

You can convert the dihydrate back to the hemihydrate by baking it at 150F for several, perhaps many, hours. It should then crumble easily.

An estimate of how long?

[chemisttree]

An estimate of how long?

For the heating step? It should take from 2-4 hours but depending on the maximum cross section the water must traverse on the way out, that could increase significantly... perhaps as much as a day or more.

This article has some information that might be helpful. (http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1432.pdf)

This thread also discusses a similar problem. (http://cr4.globalspec.com/thread/25981/Gypsum-dehydration)

I like the idea of microwave heating. Heat slow at first and then ramp up the power.