Thank you Andreas, what % is the Ammonia, around 10% maybe?
I am preparing new solution from the powder now, that Congo Red is strange.
I take the long cut, I dissect and put the section in congo red. Leave for a minute or so, then I absorb the extra stain with a cotton bud or kitchen roll strips and add plenty of 3%KOH and wash the dissection in it (sometimes leave it to stand for another minute if the tissue is robust/hard). Then I pick the washed section and place it in a drop of KOH+Glycerol mixture, sometimes a dissect further in smaller pieces and space them out. I place the cover slip over, press with a rubber over tissue paper and ready to go. The glycerol mixture prevents the slide from drying.
Cheers