I ran into a curious Gum problem. I am a new gum printer, so this may seem basic to more experienced folks. Recently I switched my sizing formula from hardening with Glyoxal to Glutaraldehyde. My sizing problems were resolved by the change. At the same time, my old supply of gum ran out and I opened a new container (from Photographer's Formulary). Suddenly I observed an increase in required exposure of about 3x (1.5 stops). Since I changed two variables at the same time I am uncertain about the cause of the sudden increase in required exposure. I doubt it was the change in my sizing formula and I suspect that the change from "old gum" to "new gum" is the culprit. Has anyone else experienced this kind of change and does anyone have any idea what may have caused it? I would appreciate any insight.