Ioxoi - 12-4-2008 at 06:17
Hi Guys,
For the longest time the best and biggest alum crystals I've ever seen were only an inch or two across and were made by professional labs, not
homegrown in sheds.
But check out some of these videos!
http://www.youtube.com/watch?v=D8biJebYq7I
http://www.youtube.com/watch?v=jMLwXJyB2K4
http://www.youtube.com/watch?v=DLgudiLrUjM
Apparently "Crystallographie" has figured out some bizarre way of growing gigantic pyramid crystals using a glass plate with a small hole in it to
initiate crystal growth. If you check out his profile he has other videos, some with him trying to explain his method. Unfortunately he is
French-Canadian and it's kind of hard to understand what he did to construct the glass plate generators, because he speaks mostly French, and his
English is somewhat broken.
Some of those crystals he's made look like they weigh several pounds! 
In any
case, he is a home experimenter and has done it with readily available equipment. Can anybody figure out how he has been doing this???
Here he holds his pyramids upside down.
http://charlevoix.qc.ca/cristallerie/p_album_03.jpg
Here are some of them, upright.
http://charlevoix.qc.ca/cristallerie/p_album_02.jpg
[Edited on 4-12-2008 by Polverone]
Klute - 12-4-2008 at 13:13
Well, i find it to be pretty well explained in these videos:
http://www.youtube.com/watch?v=Hy42_yDmkpQ&feature=relat...
http://www.youtube.com/watch?v=GqiKTFUADD0
Apparently he has a kind of system recirculating a hot saturated potassium alum solution, agitated over those glass generators. The little seed
crystals embedded in the hole regrows a pyramide. I guess the quality of the seed crystals decides of the pyramide you can obtain...
I find it very generous on his part to share his technic. Others would surely be selling the crystals at outraging prices and keeping the secret to
themselves... I would be surprisedif he doesn't sell them though. 
If you have questions for him or whatever, i can always contact him, being french myself. PM me in that case.
[Edited on 12-4-2008 by Klute]