To grow crystals, you need to start with a saturated solution – water that has as much, sugar, salt or whatever crystal ingredient dissolved in it as it possibly can. Gently and carefully warming the solution in a saucepan, in a bath of hot water or on a radiator and stirring it will help more ingredients dissolve into the water.
To grow small crystals, leave the solution in the glass or pour it into saucer and let the water evaporate, leaving the crystals behind, or soak a piece of cardboard in the solution and leave it to dry. Pour the solution onto a hot glass dish or hot baking tray to get sheets of crystals.
To grow a string of crystals, hang a thread or string from a wire, toothpick or pencil balanced on the top of the glass into the solution and leave the crystals to form.
To grow a larger crystal, use a small crystal as a seed crystal, either grown on a string, or tied on to a piece of nylon fishing wire. Hang this in the solution in a clean container. Put the glass somewhere quiet, where it will not be knocked. If your crystal starts to dissolve, or isn’t growing, the solution probably isn’t saturated enough.
To grow stalactites and stalagmites, fill two jars with a saturated solution, put a strip of fabric between the two jars with the ends in the solutions. The middle of the strip should hang a bit lower than the tops of the jars. Let the solution drip from the middle of the strip into a saucer – a stalactite should hang from the strip, and a stalagmite start to form in the saucer.
Once the crystal has finished growing, keep it in a dry container.
It is probably a good idea to wear gloves when handling all the solutions (except salt and sugar), and do not drink any of the solutions (even ordinary salt at very high concentrations could make people ill).
Crystals are made from repeated patterns of molecules, and grow layer by layer. Different solutions will make crystals in different shapes. Some might be cube shaped, others might grow in columns.
What Crystals Can You Grow?
Many ingredients for growing crystals can be found around the house or in grocery shops, supermarkets and chemists.
- Salt (sodium chloride) is used to flavour food (but not too much – it’s bad for your heart).
- Epsom salts (magnesium sulphate) is used in bath salts and in gardening.
- Bicarbonate of soda (sodium bicarbonate) is used in cooking and in eco-friendly cleaning.
- Borax (sodium borate, sodium tetraborate, or disodium tetraborate) is used in eco-friendly cleaning.
- Sugar crystals are known as rock candy – try adding flavourings and colourings (and watch to see if these change how the crystals grow).
- Alum (aluminium potassium sulphate) is used as an antiseptic and to stop bleeding, for example after shaving, and occasionally used in cooking.
- Washing soda or soda crystals (sodium carbonate) are used in eco-friendly cleaning.