My experience is that #55 film is tough for good dense negatives. the
positive sheet is rated at about 50 asa, but the negative is at around
asa 25. so you must overexpose the positive at least one stop to get
the negative with more exposure on it. Still with overprocessing at one
to a minute and a half, still is a weak neg compared to tri x or other
materials. But it is fast and easy.
I was working in plat/pall with these negatives. I have an example of
a print with 55 in my web site. it is Donine under general portraits.
Gary Auerbach
http://www.azstarnet.com/platinum