Are you sure about this?
Originally Posted by Photo Engineer
I've tested a LOT of surfactants and biocides before settling on the ones I use, but the difference in the biocides is minimal, as long as they are added to the finished emulsions. Both phenol and thymol are very old generation biocides and there are better ones that are safer to humans and environments, and inexpensively available because they are used in many industrial applications. I've tried all sorts of stuff but the choice of biocide is rather irrelevant to photographic property (except for certain quarternary ammonium salts), and the choice can be made by the biocide functionality alone.
Surfactant is also a very important factor in making beautiful prints, but I see little need to change the surfactants added to the sizing, subbing, emulsion or overcoat layer to accomodate the differences among paper stocks. The surfactant choice is more strongly influenced by the coating speed, coating method, emulsion viscosity and the coating temperature.
I don't know how fast you coat, but unless you are coating at the industrial speed, there are many surfactants that work very well.
There is a larger issue that is not mentioned in your post. The binder system in modern emulsions incorporate nongelatin polymers in a small proportion (5 to 40%). The formulation of the binder system has a large impact on the quality of coated layers, such as swelling property, wet strength, brittleness, etc. If you are having problems in obtaining good coating, you should be looking at these issues together with the coating speed and temperature issues, because they are mutually dependent factors.