I was studying Inorganic Chemistry today and I read a statement for which I wasn't able to understand the meaning.

When Plaster of Paris is wetted with water,it forms a plastic mass which sets in from 5 to 15 minutes to a white porous hard mass.

I can understand that Plaster of Paris is treated with H2O. I cant understand next sentence . Can anyone explain this is in simple English?

  • I think you omitted a word, and I think it might have been water. Is it correct that you meant to say that it is wetted with water? – ringo Mar 9 '16 at 5:53
  • yes it is treated(wetted) with water – Math Boy Mar 9 '16 at 5:53

Plaster of Paris initially is in the powdered form. When it is mixed with water, it undergoes few chemical reactions and forms a plastic-like substance in about 5 to 15 minutes. It is porous. That means that the plastic-like has small holes in it.


You're missing some words. Here's the full quote from Modern Inorganic Chemistry by Joseph William Mellor:

When plaster of Paris is wetted with, say, one-third of its weight in water, it forms a plastic mass which "sets" in from 5 to 15 minutes to a white. porous, hard mass.

Clear now?


Breaking it into stages:

Plaster of Paris - (original form is a powder) - when wetted mixed with some water it forms becomes a plastic easily reshaped mass lump which sets becomes a solid in a period of time from lower limit 5 to upper limit 15 minutes to becoming a white porous full of little holes hard not easy to reshape mass.

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