I got involved with vermicomposting almost 5 years ago and have used mainly black-and-white newspaper (which I knew to use a "safe" type of ink), egg cartons, and coir for bedding. I've been concerned because my source of "safe" color-free newspaper has disappeared and I didn't think an all-coir bin would be a good idea. I read your posting about using cardboard, which sounds like a wonderful idea and would solve my paper-shortage problem.
However, is any type of cardboard safe and healthy for composting worms? I've read that there are many types of cardboard -- is the type you use corrugated fiberboard that's used, for example, for shipping boxes? Should I use only plain cardboard with no print or glue in my worm bins, or is the ink and glue used on cardboard of no concern?