Although it is not very clear from your question, it appears the problem has to do with growing crystals. There are a number of difficulties one can encounter while growing crystals:
- No crystal growth: this is a common occurrence when the solution is not saturated. In such a case, add more solute to the water. Heating and stirring helps with saturating (and super-saturating) a solution. If you see a small amount of solute at the bottom of your cooking pot, try dissolving it (by stirring) or wait for it to dissolve. Keep on adding solution till you see some undissolved solute at the bottom.
- To much vibration or disturbance can cause non-growth of crystal. Keep the container in an undisturbed area.
- Contamination: sometimes the solution can pick up contamination from the solute, residue from the paper clips or thread, unwashed detergent on the pan, etc. In such a case remove the contaminant and start afresh.
- Inadequate temperature: sometimes the temperature has to be increased or decreased for crystallization to take place.
- Rate of cooling may be too slow and can be assisted by lowering the temperature of the solution (you can put it in an ice bath or refrigerator, etc.)
- Sometime you may also get parasite crystals (small particles that crystallize on the sides of the big crystal). Try to remove them as gently as possible.