Australia's Science Forum

What achieves the best results. I was taught to put a couple of mls of saturated soln in a larger petri dish and put in the fridge. The cooler temperature in the fridge is supposed to stop a lot of very small crystals forming, but this is what happens. I have tried leaving the dish with soln on the bench for a while before putting it in the fridge. Either way I end up having to pick out the most uniform crystals and putting them in another dish with soln and I wondered if there was a more certain way of ensuring formation of good sized crystals. I live in the far north of WA so the conditions are hot and humid in summer and dry and cooler in winter.
All help appreciated.

Regards
Diane

I obtain bigger crystals by keeping the container in a warm place and reducing the rate of evaporation to a minimum. I use a disposable plastic food container with a cm depth of saturated solution and leave the lid covering in place except for a narrow gap at one end.
Cheers,
Fran

Hi All,

The slower the rate of cooling the larger the crystals will grow, placing a seed crystal in with the solution will entice the crystal/s to begin growth.

Fast cooling rapidly forms small crystals (Just use granite as an example... as the ignious rock cools quickly the smaller crystals form).

Cheers,

Robb.....

Thanks robb and franco for your help

Regards
Diane