Some recipes for growing crystals include mixing three tablespoons of borax with a cup of boiling water or mixing equal parts Epsom salt and hot tap water. Salt crystal geode recipes call for only hot water, salt and an eggshell, while recipes that mix copper sulfate and hot water produce crystals that are vivid blue in color.
Crystals are solid materials with molecules arranged in an orderly repeating pattern. Crystal growth is a major part of the crystallization process during which additional atoms, ions or polymer strings join together, forming a crystalline lattice. Crystal growth produces a crystalline solid with very tightly packed atoms and molecules that have fixed spatial positions relative to each other.
Many recipes for growing crystals call for hot or boiling water, since crystallization typically occurs when molten liquids cool and solidify from their molten state. Crystals form in two stages, nucleation and growth. During the nucleation stage, materials must impinge on each other and achieve the correct orientation and placement. Crystal growth occurs far more rapidly than nucleation and takes place as new materials form in a prearranged system, known as a crystal lattice. These materials spread outward from the nucleating site. Many recipes require only a few hours or day to produce crystals.