How do you dissolve plaster of Paris?

Answer 1

"I think vinegar is supposed to work.

Lawren1

The CRC Handbook of Chemistry and Physics (65th ed. Special:Booksources) lists plaster of Paris (calcium sulphate half-hydrate, CaS04.1/2H2O) as soluble in acid, ammonium salts, sodium thiosulphate (Na2S2O3) and glycerin."

I am so surprised that so many people on so many forums, obviously don't have a clue about the chemistry of plaster of Paris. I read in so many places things like "uh, try some kind of acid..."

So I have a lot of concentrated chemicals on hand and did lots of experiments with all kinds of acids, both dilute and concentrate, under many conditions and determined that none of my dozen or so acids dissolve Plaster of Paris in any way, but sometimes make it harder.

The chemicals which dissolved plaster of Paris are on the basic end of the PH scale, not acid. I first had some success with potassium cyanide, but what really worked better than anything is Sodium Bicarbonate. Makes sense. The sodium in baking soda hooks up with sulfur in the plaster, and the carbon hooks up with the calcium in the plaster.

TO BEST DISSOLVE PLASTER OF PARIS PLACE IT IN WARM WATER WITH LOTS OF BAKING SODA.

Don't use any acids or it will only defeat the process.

Now what really amazes me is that the answer is so simple and safe, and surely some people must know it, but it apparently cannot be found on the internet, until now.

Or you can chisel it away because it is soft enough to do so.

Answer 2

It doesn't dissolve in water. It is highly insoluble in water. But water can soften hardened plaster.

Answer 3

Keep stirring, and the water should be tepid, not warm, not cold. If not using powder , a solid piece must be pulverized

Answer 4

Plaster of Paris (calcium sulfate) is decomposed by heating.

Answer 5

-66 oC