You might try this
Tannic acid bath (blue/brown to purple)
5min in tannic acid followed by soaking the print in sodium
carbonate then wash the print.
Tannic acid 6 grams
Water 180 ml
Sodium carbonate 6 grams
Water 180 ml
give this a try, as I remember I once mixed this up using Sodium
bicarbonate with out much differance.
from 1 of those 500 lurkers that Sullivan talks about
xoxoxoxojp2/jpp