There may come a time when you will try to grow a crystal without success. Here are some ideas for possible problems and ways to correct them:
No crystal growth
This is usually caused by using a solution that isn't saturated. The cure is to dissolve more solute into the liquid. Stirring and applying heat can help to get solute into solution. Keep adding solute until you start to see some accumulate at the bottom of your container. Let it settle out of solution, then pour or siphon the solution off, being careful not to pick up undissolved solute. If you don't have any more solute to use, you can take some comfort in knowing that the solution will become more concentrated over time, as evaporation removes some of the solvent. You can speed this process by increasing the temperature where your crystals are growing or by increasing air circulation. Remember, your solution should be loosely covered with a cloth or paper to prevent contamination, not sealed.
If you are sure your solution is saturated, try to eliminate these other common reasons for lack of crystal growth:
Too much vibration
Keep your crystal setup in a quiet, undisturbed location.
Contaminant in the solution
The fix is to re-make your solution. The fix only works if you can avoid contamination (won't work if your starting solute is the problem). Common contaminants include oxides from paper clips or pipe cleaners (if you're using them), detergent residue on the container, dust or something else falling into the container.
Experiment with temperature. You may need to increase the temperature around your crystals to get them to grow (increases evaporation). For some crystals, you may need to decrease the temperature (which slows the molecules down and gives them a change to bind together).
Solution cooled too quickly or slowly
Did you heat your solution to saturate it? Should you heat it? Should you cool it? Experiment with this variable. If the temperature changed from the time you made the solution to the present time, the rate of cooling may make a difference. You can increase the rate of cooling by putting the fresh solution in a refrigerator or freezer (faster) or leaving it on a warm stove or in an insulated container (slower). If the temperature didn't change, maybe it should (heat the initial solution).
Water wasn't pure
If you used tap water, try re-making the solution using distilled water. If you have access to a chemistry lab, try deionized water that was purified by distillation or reverse osmosis. Remember... water is only as clean as its container! The same rules apply to other solvents.
Too much light
An unlikely problem with home crystals, but for certain materials the energy from light can inhibit the formation of chemical bonds.
- Too much vibration
No seed crystals
If you are trying to grow a large single crystal, you will need to get a seed crystal first. For some substances, the seed crystals may form spontaneously on the side of the container. For others, you may need to pour a small amount onto a saucer and let it evaporate to get crystals. Sometimes crystals will grow best on a rough string suspended into the liquid. The composition of the string is important! You are more likely to get crystal growth on cotton or wool string than on nylon or a fluoropolymer.
Seed crystals dissolve when placed in new container
This happens when the solution isn't fully saturated. See above for details.