Red Rain Problem Solved following Steve Toth's Observation

Bruce Bruce
Sat Dec 14 20:17:54 EST 1996

Hi all,
	Here's a copy of the e-mail I just sent to Steve Toth.

        IT WORKS!!!! No more red rain!!!!  What we did was to follow your
advice and within various times after pouring the gels, covered the lower
end of the glass plates with a water moistened paper towel.  We made
sure not to have the towel touch the bottom of the glass so as to avoid
any capillary action that would cause the gel mix to be drained from
the bottom of the gel, and like magic, we no longer are having the red
rain problem.  Because it's pretty dry here in Oklahoma, we also are
covering the draped paper towel with a piece of Saran Wrap to prevent
evaporation of water off the towel.  We've waited as long as 45 minutes
prior to adding the moist towel but 45 minutes seems too long as some
slight red rain did occur.  It's just as easy to add the water moistened
paper towel within 5 minutes after pouring, as long as care is taken to 
drawing out any of the gel from the bottom by capillary action prior to it
being completely polymerized.   Then, after about 2 hours, we seal both
the bottom and top with a moist paper towel wrapped with Saran Wrap and
store the gels for at least 24 hours in a drawer prior to use as we have
done for years.

        It's my semi-educated guess that when the gel dries out at the
bottom (or top for that matter) and sample with "salts" and heat is 
the gel shrinks slightly and pulls away from the glass.  Supprisingly this
occurs several cm from the end and the void between the glass and the
polymerized but shrunken gel is filled with water/buffer that has a 
refractive index than the gel itself.  Thus the "bubbles" develop and we
see "red rain".

        As far as I'm concerned, placing the moist paper towel over the
lower end of the gel and avoiding contact with the polymerizing gel mix
at that end has SOLVED the "red rain" problem.

Thanks and a tip-of-the-hat to you for suggesting the earlier addition of
the moist paper towel to keep the area at the bottom of the gel from 
out prior to complete polymerization of the gels.


Bruce A. Roe, Ph.D    Department of Chemistry and Biochemistry
                      University of Oklahoma, Norman, OK 73019-0370, 
Phone: (405) 325-4912 or 7610;  FAX: (405) 325-7762;  e-mail:  broe at

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