I’ll be teaching full-time for a few weeks now, and don’t have much time for alt-photo work of my own. However, I’ve been thinking of gum printing too, and here are a couple of things that I must consider to get students involved more easily:

Paper: Got to find good, dimensionally stable paper with good wet strength.
Sizing: Thought I could manage without extra sizing, but it looks like it’s just necessary to size certain papers. Also, I need to determine which sizing method to use.
Pigments: Finding an assortment of good quality non-staining pigments.
Negatives: Proper correction curves; it may be necessary to generate separate curves for each color (in 3 and 4-color work) instead of single generic curve common to all colors.

By the way – good news about Varn gum! We can get it again – our supplier was able to make a special order from Germany. It will make our life a little bit easier, with no need to mix the gum from powder or lumps…