See the following publications:

Emmel VM & Stotz EH 1986. Certified biological
stains: a stability study. Stain Technol.
61:385-387.
Titford M 2001. Comparison of historic Grubler
dyes with modern counterparts. Biotech. Histochem.
76:23-30.
Titford, M. 2002. Save that dye! Microscopy Today
18-5:31-34.

The general conclusion is that nearly all dye
powders still work after 100 years (Titford).
Quantitative assays show very little deterioration
over 20 or so years (Emmel & Stotz). Matt Frank
may have more recent information from the
Biological Stain Commission's lab.

Alcian blue 8G can deteriorate in the solid state,
changing to an insoluble pigment. This is not a
problem with the pyridine variant of alcian blue
(Churukian et al 2000, Biotech. Histochem. 75:
147-150). Acidic solutions of alcian blue 8G are
stable for some years on my shelves. Churukian's
lab manual gives a recommended shelf life of 6
months. An alcian blue solution with a precipitate
should be discarded and replaced, not filtered and
used.
-- 
-------------------------------
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
   kiernan[AT]uwo.ca
   http://publish.uwo.ca/~jkiernan/
   http://instruct.uwo.ca/anatomy/530/index.htm
_______________________________
Sharon E Willman wrote:
> 
> Hi,
> What is the expiration time for dry stains and how often should you
> replenish?  Many times they do not have expiration dates on them when
> they come in from the manufacturer.
> I would appreciate any information on this matter.
> Thanks,
> Sharon Willman
>

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