Polyethylene glycols ("PEG") are emulsifiers and surfactants, not
humidifiers, and have no connection to glycerin. The main uses in
photography are (1) to prevent spotting when used as a final wetting bath
(the water runs off very quickly), and (2) as an accellerator in solutions
resulting from the immediate wetting and penetration of the paper, film, or
whatever surface.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net