Carolyn N. Kinder
There are two simple methods for growing crystals. They can easily be grown from solution and evaporation. A crystal never loses its ability to grow whereas a living cell does. Dry crystals remain dormant. They will always grow more when placed in a solution which is growing similar crystals. A crystal needs substance to grow from. Where there is no substance, for example at points where crystals come in contact, the crystal stops growing.
Crystals will now grow from any solution of its own substance. A crystal growing in a drop of solution will begin to dissolve again if a drop of water is added to the drop of solution. The crystal will again start to grow when this added drop of water has evaporated. Crystals are very choosy about the conditions under which they grow.
Two Methods Of Growing Crystals
There are two general methods which are convenient for growing certain crystals. In both, you suspend a seed crystal by a thread in a jar of solution. In one, the sealed jar method, you supersaturate, or make more highly concentrated than the normal saturated solution and seal the jar to keep water from evaporating. The seed will grow as excess salt in the solution slowly crystallizes on it.
In the other method, growing by evaporation, you start with a saturated solution, a solution that is completely filled, and permit it to slowly evaporate. The jar is not sealed, but the top reduces, the rate of evaporation and keeps dust out of the solution. The crystal grows as water evaporates.
In both these methods even temperatures are important because temperature changes alter the amount by which the solution is supersaturated. Refer to growing crystals in the book,
Crystals Insects
,
and Unknown Objects
, by John McGavack Jr. and Donald P. LaSalle, Page 143.
The first step in either method is to make a saturated solution, one that is saturated at the temperature at which the crystals will grow. Making saturated solutions requires time and patience. Refer to recipes for crystal growing in the book
Crystal and Crystal Growing
by Alan Holden and Phyllis Singer, pages 108 to 119.
Both methods of growing crystals have advantages and disadvantages. The evaporation method allows a progressive supersaturated of solution. This allow you to get back all of the solid in the form of a single crystal. The rate of evaporation is hard to control. It depends on the humidity of the environment and how often casual drafts remove the evaporated moisture. Since evaporation takes place at the surface of the solution, the supersaturation tends to be greatest there and factitious or artificial seeds often form at the surface and may drop on the desired crystal. In the sealed jar method, supersaturating the solution by cooling it below its saturation temperature is only as effective as your control of the temperature of the environment. As the crystal grows, the supersaturation declines, and then automatically provides the slower growth rate usually desirable for larger crystals. The amount of material which can be deposited from the solution is limited to that amount originally dissolved in the saturated solution when it was made. Probably the quickest way of growing crystals is by use of the sealed jar method. For more information on crystal growing, refer to the unit developed by Lois R. VanWagner on “More Than Meets the Eye: The Story of Crystals”, Crystals in Science and Technology, Yale New Haven Teachers Institute, 1989.