<< The good news is that they probably don't fade! It is assumed that the
prints
look today just like they did. Others may have a different opinion on that.
>>
I don't know much about the process and haven't seen any image made from the
process, but I think they all fade. From the description I read, it is the
fading (by sun light) that makes the whole process works, is it not?
<< The bad news is Dan, that according to source in Oxford, exposures did
take Herschel in the vicinty of a week. >>
Different vegetable/plant dyes fade at different rate. Slower-fading dyes
might take longer to exposure (since exposure basically makes the dye fade)
but might keep longer too.
If anyone is interesting in trying different dyes, you can go to a library
and check out books on dyeing. There are plenty of books that list the colors
of different plants. I think this would be a good school project but not for
permanent prints. Dyes die. They all fade.
David Soemarko