How to make rock candy

Growing sugar crystals at home

Safe­ty pre­cau­tions

Only un­der adult su­per­vi­sion.

Equip­ment and reagents

  • pan;
  • saucepan;
  • sug­ar;
  • loll ipop sticks;
  • pa­per tow­el;
  • food col­or­ing;
  • glass;
  • binder clip;
  • foil.

Step-by-step in­struc­tions

Melt 100g sug­ar in a fry­ing pan. Cov­er some lol­lipop sticks with the re­sult­ing vis­cous mass and roll them in sug­ar. Mix 600g sug­ar with 200mL wa­ter and put over medi­um heat. Add a few drops of food col­or­ing. Boil un­til the sug­ar dis­solves com­plete­ly. Pour the sat­u­rat­ed sug­ar so­lu­tion into a glass and im­merse a sug­ary stick in it. Cov­er the glass with foil and fix the stick in place us­ing a binder clip. In 3-4 days, in­tri­cate sug­ar crys­tals will grow!

Pro­cess­ de­scrip­tion

At room tem­per­a­ture, the sol­u­bil­i­ty of sug­ar in wa­ter hov­ers around 200g per 100mL of wa­ter, but when heat­ed, the sol­u­bil­i­ty of sug­ar in­creas­es, mean­ing that more of it can dis­solve in the same amount of wa­ter. At 100 оС (212 °F), the sol­u­bil­i­ty of sug­ar in wa­ter is around 487g/100mL of wa­ter. When cooled, the so­lu­tion be­comes over­sat­u­rat­ed, i.e. more of the sub­stance is dis­solved than can stay in the so­lu­tion at the giv­en tem­per­a­ture. To make the sug­ar crys­tals grow on the stick and not just pre­cip­i­tate, we in­clude a seed for crys­tal­liza­tion (i.e. sug­ar crys­tals). Thus, the “sur­plus sub­stance” pre­cip­i­tates in the form of crys­tals, and the so­lu­tion once more be­comes sat­u­rat­ed. In just a few days, the sug­ar grains will grow!

Want to grow your own crys­tals? If so, you’re sure to like the ex­per­i­ments in the “Crys­tals” set from the MEL Chem­istry sub­scrip­tion!