Quote Originally Posted by DKT
There's a theory that rc paper is more sensitive to pollutants than fiber because the emulsion is lying on top of the support. the base traps pollutants and they can attack the image from both sides. With fiber , the theory goes, it allows pollutants to pass through and the damage is slower.
Camera and Darkroom had an extensive analyis of RC paper and compared it to "Fiber -Based" (actually not true - both RC and "Fibre" can have a paper fiber "support" - a *few* RC papers are consrtucted with a plasitic - Polyethethelene? - core). Both papers have emulsions that "Lie on top of the base"... and the "base" in both cases lies on top of the support - the difference is in the polyethelene encapsulation of the "support" of RC papers...Being impervious to chemicals and water itself, washing and drying times- and curling - are drastically reduced.

Base materials are different - "Fiber" papers use "baryta" - a white clay: RC uses Titatnium Oxide - a pigment used widely in white paint.

Its hard to envision RC emulsions and bases "trapping" pollutants - where they "soak" into the fiber support with no PE encapsulation, it seems to me that they would hang around considerably longer and have a more pronounced effect on image degradation.