Growing crystals is a fun, hands-on way to study chemistry and look at basic principles of geology and mineralogy. While some simple crystals can be made at home without special assistance, a science kit can provide a valuable starting point for getting larger and purer crystals. Many students grow crystals as part of a science kids chemistry kits fair project, examining different factors and conditions.

Every time you grow crystals, a chemical reaction takes place. Two or more chemicals are combined to create a new product. Typically, these initial chemicals are dissolved in a solvent. Once they combine to form a new substance, the saturated solution is allowed to cool. Crystals form slowly as the temperature drops. As individual particles touch, they join to form a crystal and fall out of solution. The solid product settles to the bottom - a process known as precipitation. This chemical reaction can be performed at home, but it mimics the same conditions that take place whenever crystals form - including during geological formation.

A crystal is made up of repeating molecules held in a solid structure known as a lattice. Even common household crystals, such as sugar and salt, form by precipitating out of a chemical solution. Under optimal cooling conditions, the resulting crystals have increased size and clarity. Another important factor is the purity of the solution, as any unwanted impurities will affect crystal formation. For this reason, students wishing to grow crystals for a science fair or other project may prefer to start with a science kit and the provided chemicals.

Providing an initial seed crystal helps grow crystals larger. One simple method involves suspending a string into the solution and letting small crystals form. Another option is pouring a small amount of solution onto a plate and letting it evaporate to leave crystals. These small crystals are the seed crystals. Next, suspend a seed crystal on a piece of fine nylon string or dental floss. Dangle it into a clean container of saturated solution and allow the crystal to grow. If additional crystals form inside a container, transfer the seed crystal and solution into a new container. Otherwise there will be several smaller crystals rather than a single large one.

It takes time to grow crystals, since the solution must evaporate. For some solutions, stirring or heating can speed the process. If a crystal appears to be shrinking, more liquid should be added to the solution. Water is the most common liquid, but other solvents are possible. Experimental manipulations include changing the rate of evaporation, changing the rate of cooling, adding impurities, or using different solvents. Students can test the effects of humidity, vibration, container type, string type, and light.