Calcium sulfate: a construction pro

How to make crafts from gypsum

Cal­ci­um sul­fate has been used since an­cient times — in build­ing and con­struc­tion, in sculp­ture, and even in med­i­cal ser­vices!

Safe­ty pre­cau­tions

Ob­serve safe­ty mea­sures when work­ing with these com­pounds. Wear pro­tec­tive gloves, a mask, and safe­ty glass­es while con­duct­ing the ex­per­i­ment.

Reagents and equip­ment

  • 70 g of cal­ci­um sul­fate (al­abaster);
  • a sil­i­cone mold;
  • a glass con­tain­er;
  • a food col­or­ing;
  • 100 mL of wa­ter;
  • a spoon;
  • 20% sul­fu­ric acid so­lu­tion;
  • 20% cal­ci­um ni­trate so­lu­tion.

Step-by-step in­struc­tions

To ob­tain cal­ci­um sul­fate di­hy­drate, sim­ply mix so­lu­tions of sul­fu­ric acid and cal­ci­um ni­trate. In or­der to pre­pare a gyp­sum so­lu­tion, mix it with wa­ter in a 7:10 ra­tio. You may also add a tiny bit of food col­or­ing to the so­lu­tion. Now, place the ob­tained mix­ture into the mold and leave it there for 20—30 min­utes to so­lid­i­fy.

Cal­ci­um sul­fate also oc­curs in na­ture in form of min­er­als — gyp­sum (cal­ci­um sul­fate di­hy­drate) and its an­hy­drate (an­hy­drous cal­ci­um sul­fate). In a lab, gyp­sum Ca­SO₄×2H₂O can be syn­the­sized by mix­ing the so­lu­tions of sul­fu­ric acid H₂­SO₄ and cal­ci­um ni­trate Ca(NO₃)₂, which yields a white crys­talline pre­cip­i­tate.

Ca(NO₃)₂ + H₂­SO₄ + 2H₂O = Ca­SO₄×2H₂O + 2H­NO₃

If you were to add wa­ter to al­abaster, it would even­tu­al­ly so­lid­i­fy with the for­ma­tion of a durable ma­te­ri­al. It is of­ten used in con­struc­tion, in sculp­ture, and even for bone fix­a­tion in case of frac­tures.