c Grow large crystals i Use a 05  08 cm long seed crystal to start growing large crystals Make seed crystals by slow evaporation of 30 mL of saturated solution in a glass dish Dry a selected seed crystal Tie a piece of clean cotton around it without touching the seed crystal with your hands because impurities easily affect the size and shape of the crystal Hang the seed crystal 5 cm from the base of the container with a bent wire Fill a jar with a screwon lid with a solution of the salt less than saturation strength before you put the seed crystal in position If little crystals grow on the surface of the seed crystal then screw on the lid of the jar to make the little crystals dissolve Prevent crystals growing on the sides of a crystallizing dish by rubbing Vaseline round the upper inside rim Evaporation may be increased by sitting the crystal growing jar on a tin with a 5 watt bulb mounted inside it An air flow over the solution surface given by a fan will also hasten crystal growth You can preserve large crystals by painting with a clear varnish ii You can also support the seed crystal at the end of a glass tube Heat a 3 mm bore piece of glass tubing in a flame until the end softens sufficiently to squeeze with pliers to make a smaller hole When the glass tubing cools drop seed crystals on its end until one catches in the smaller hole Keep this crystal in place by dropping other crystals on it Support the glass tubing vertically so that the seed crystal at the end is immersed in the solution of the salt The seed crystal should then grow Turn the crystal regularly so that growth on all faces is equal