Sciencemadness Discussion Board

Growing a large transparent alum crystal

CoolFool - 11-12-2017 at 22:45

The seed crystal i chose was pretty transparent. But the crystal didn't turn out as transparent as i wanted. Is there any steps that i could take to increase the transparency? Also how can i grow the crystal so that it shows a geometric shape?

CaCl2 - 13-12-2017 at 23:09

1. Slow the evaporation speed down, partially cover the container with paper or something.

2. Make sure that the temperature of the container stays stable, alum has a higher solubility in hot water than in cold, repeated dissolving and crystallizing makes the crystal less clear.

3. Make sure to avoid impurities, use distilled water, maybe recrystallize your alum.

4. To achieve the characteristic alum shape, you have to attach the seed crystal to a thin, transparent piece of string, and then suspend it in the middle of the solution, so that it doesn't touch the bottom.



[Edited on 14-12-2017 by CaCl2]