I wait about a minute before I turn on the white light. However,for many years I turned the lights on as soon as the print was was in the fix. I stopped doing this when I began to notice that the print has a tendency to change tone after about a minute in the fix. This is especially noticeable when using Forte Poly Warmtone. There is most likely no detremental effects but I now wait the extra minute under safelight for peace of mind.(posted 8078 days ago)