The method goes as such:
Run the gel with 0.5X TBE in the top tank and normal 1 X TBE in the bottom tank. Just after the last (or in the case of one load - the only) load has run into the gel, put a half volume of 3 M sodium acetate in the bottom tank (make sure you leave enough room - I use 300 ml 1 X TBE and 150 ml 3 M Na acetate in my BRL S2 gel box).
This causes a themal gradient across the gel - the bottom is relatively cool and the top gets quite hot to touch. This causes the bands to run closer at the bottom.
A few points:
use normal acrylamide made in 1 X TBE and urea.
the gel takes half as long again to run.
if you go over 65 - 70 W, the plates crack, especially old ones.
I haven't tried not fixing it, but I see no problem.
I fix for 20 min and dry for 20 min.
I only ran 3 or 4 wedge gels but I couldn't stand the dry times, but the results appear comparable - my friends who still run 'em agree with me.
I hope this is useful.
John Nash (Internet:) Nash@biologysx.lan.nrc.ca.
Email to my other addresses is forwarded automatically,
Disclaimer: All opinions are mine, not NRC's!