John Kiernan posted a detailed note about the use of Sirius red as a collagen 
stain.

Holde Puchtler and her group introduced Sirius red, Sirius supra scarlet, and 
a couple of others as amyloid stains. These direct cotton dyes, which were 
then very popular in the textile industry, were supposed to replace Congo 
red, a dye long out of use in the textile industry and manufactured only for 
histologic use. Congo red at that time was quite unreliable as an amyloid 
stain, with great batch to batch variations.

Why didn't Sirius red replace Congo red? As near as I could figure out, 
improvements (probably through the efforts of the Biological Stain 
Commission) in Congo red were part of the answer, but the very great 
influence of George Glenner and David Page's work on the nature of amyloid at 
about that time - using only Congo red - seemed to seal the fate of the newer 
dyes.

I believe that in the textile industry direct cotton dyes were largely 
replaced by reactive cotton dyes (such as the Procyon series of dyes) quite a 
few years ago.

For the small hospital pathologist, amyloid staining is often compromised by 
the difficulty in obtaining control material (apparently experimental animal 
material is not considered acceptable) and by the fact that the small 
hospital pathologist is not usually permitted to have a polarizing system in 
his microscope.

Bob Richmond
Samurai Pathologist
Knoxville TN