I've got another quandary...
I recently bought a job lot of old Orwo stuff, and in it were a few packets of Orwo A49, made in 1976. I've also previously bought Orwo A49 made in the late 1980s, and I have some modern Calbe A49.
I was suprised when I opened the 70s Orwo A49 - it contained three packets of chemicals to be dissolved in water. The 80s A49 and the moden Calbe A49 have only two.
I seem to remember reading that Atomal/A49 was reformulated at some point, because one of the ingredients, HEAP, was no longer available. Is this the reason for the apparent difference between the 70s A49 and the others? Does anyone have an opinion on which is better?
Finally, how long will stock solutions of each of these keep? Googling suggests anywhere between 1 month and 6 months.
Thanks for any help!