Ask A Scientist Chemistry Archive

Question:  My name is Tanisha Woods. I would like to know how I could grow crystals.

Answer:  One way is to dissolve a LOT of sugar into very hot water 
(make a supersaturated solution) and pour it into a glass. Before 
you do this, tie a piece of string to a pencil which will reach all 
the way to the bottom of the glass when you straddle the pencil across 
the top of the glass.  Dampen the string and roll it in a little extra 
solid sugar.  These small crystals will act as a "seed" for growing the 
larger ones. Crystals have to have a seed to form, some kind of surface 
which is similar to the crystal structure of the whole solid. Small 
crystals are ideal seeds to form larger ones.  Now, pour the water 
into the glass, and carefully/slowly lower the string into the hot 
sugar solution in the glass. Let it sit for several hours (be patient! 
It may take awhile). Hopefully you will observe crystals forming around 
the string. This is "rock candy." When the crystals are big enough, take 
out the string and eat your experiment!
 
THIS EXPERIMENT SHOULD BE DONE WITH ADULT SUPERVISION.
(They'll have fun too!).
 
-dr topper
 
PS: Good question!