Browing of Framed RC Paper
I usually keep my RC paper prints in albums, a few framed and put on book case or on wall. The ones in albums do not deteriorate, howeversome of the framed RC paper turned brown as shown on the picture crop from a 3.5 x 5" Agfa multigrade RC print in a small glass frame for about a year and half in a bright room, but not under direct sunlight.
The brown/orange color patches happen at the mid tone grey areas. When examined with a 20x loup, a brown patch appears to make up of great number of disconnected spots of irregular shape, a few brown spots even takes on a dark brown color. Looks like the brown color may eventually turns into dark brown.
There is a second coloring of RC paper, "silver-lining', these silver lines look like contour lines surrounding a deep black area. The silver lining is visible only when viewed at certain angle by the reflection.
Agfa multgrade RC paper and Ilford multgrade RC paper all exhibit these brownging behind glass.
At the moment there is still not explaination as to why the browning occurs only for RC paper behind glass. As some of my RC prints on the desk do not change color.
I suspect this browning may have something to do with the chlorine in tape water. During development and washing, the chlorine in water may penetrate the resin coating and react with the silver grains in the paper to form chlorine silver AgCl, which when exposed to light may turn brown. As for fibre paper, since there is no resin coating, the chlorine is not trapped.
The browning is definitely not due to residue hypo, because I usually wash my RC prints for 30-60 minutes, like I treat fiber papers. Does this make browing worse ? I don't know.
If the print is unframed, the chlorine may evaporate into the air, thus less likely to react with the silver grains.
Other people reported glass framed RC prints do not change color for decades. This hints at environment factor, such as water
Ctein wrote articles about this problem in Photo Technique. I have'nt read these articles.
The is moment, Agfa and Ilford have no real solution, except
advice people to tone the RC prints
-- martin tai (martin.tai@capcanada.com), August 27, 1999