hi denise

i went to your first link and you mention the use of collodion as an AH backing.
from personal experience when the colodion is dry inks seep in and are part of the
celluloid and it probably will work very well as a AH backing ... it's rigid too,
and the cheaper-stuff ( flexible with lanolin i think ) can be bought at some pharmacies.

i never really like working with collodion mainly because of the vapors and how flammable it is.
while it would work well and absorb pretty much any ink (or paint i am guessing) once it is dry
and it can be easily peeled off by poking up a corner and peeling off the plate, personally i'd use something else
cause i am not really a fan of such flammable stuff. .. after you peel it off, what would do with it then?
can't really dispose of the stuff in the trash, have it too close to a light bulb and you have a 2nd cleveland clinic fire

maybe just make a few of them and just reuse them ?

have fun !