[rep353]

My chemistry class are hoping to enter into a crystal growing competition. We will be making crystals from alum. We will also use pure water in the process.

What is the best procedure to make the best quality crystal and with good aesthetic quality?

[Fluorine]

Don't shake/disturb the container and be patient. Also depending on how much time you have consider redissolving the solution and evaporating again. I got fair size crystal by doing this but we had an extended duration to turn them in.

[opti384]

You should not definitely shake or disturb it. Also, leave it where it's cool.

[rep353]

Are there any good procedures?

[jeffrey.struss]

Slow evaporation, undisturbed works the best for high school level stuff.

There are more advanced techniques for when you crystals for x-ray diffraction. Things like solvent vapor diffusion, using an NMR tube that has been thinned and freezing your solvent with the analyte and layering an opposite polarity solvent on top to allow gradual diffusion. Heavily cooling down the reaction mixture and just letting it sit. etc. etc. etc.

[Borek]

http://lmgtfy.com/?q=how+to+grow+crystals