Typically, recommended fixing times and capacities are different for RC paper compared to fiber paper with the fiber paper requiring longer time and fewer sheets/volume of fix. This would seem to indicate that the emulsion sitting on a paper substrate is significantly different than the emulsion sitting on a plastic substrate. Does anyone know what the difference is???

R.

-- RICardo (ricardospanks1@yahoo.com), January 11, 2002

Answers

Response to FIXER

The capacity difference is more of a practical issue. RC papers are much easier to wash out silver complex ions that tend to remain in gelatine when fixer becomes exhausted. If you can come up with a way to wash them out effectively without exerting stress on paper fiber (bigger cells that like to swell a lot) and gelatine, you can probably fix more papers in the same volume of the fixer.

The processing time is probably due to different kinds of gelatine composition and superficial coatings. Silver content is not different to require that much difference in the processing time.

Technically speaking, the substrate of fiber based papers is traditionally some barium compounds (that determines the whiteness of the paper surface), whereas it is polyethylene in resin coated papers.

-- Ryuji Suzuki (rsuzuki@rs.cncdsl.com), January 11, 2002.

Response to FIXER

The answer you might easily get for your question is that it (certainly) takes more time for the chemical to reach all the undeveloped silver halides on a fiber based paper than on a resin- coated one. This explains the longer fixing (and development) times recommended. It does not, though, explain the smaller capacity (sqm/liter) of the chemicals for fiber papers. I tend to believe that FB papers contain more silver than the (same) RC ones, although several times I have been told that they have ABSOLUTELY the same emulsion (type and quantity). For example, Ilford claims that Ilfospeed and Galerie are manufactured with exactly the same soup (emulsion) and so they should have the same characteristics. I have, in the past, used both papers and I can assure you that the results were quite different (I don't think I have to describe which was better)...

-- George Papantoniou (papanton@hol.gr), January 11, 2002.

Response to FIXER

Just my guess, but I suspect the reduced capacity for FB is because of chemical carry-over from the developer that is absorbed by the base, which isn't neutralized by the stop bath for lack of contact time.

-- Charlie Strack (charlie_strack@sti.com), January 11, 2002.

Response to FIXER

Old films and papers often contained more silver halides than most sold today, yet they often required shorter fixation time and lower maximum density. When the manufacturers say "same sensitized material" in products X and Y, they don't mean they use identical gelatine support and superficial coatings. Fixers work even if they are diluted with some developers (not all developers). Fluid carryover is not the important determining factor of fixer processing capacity.

-- Ryuji Suzuki (rsuzuki@rs.cncdsl.com), January 11, 2002.