I just needed to put in a good plug for this book. It’s what I learned gum printing from, and contains some very useful information on other alt processes. The book is “A Non-Silver Manual: Cyanotype, Vandyke Brown, Palladium & Gum Bichromate with instructions for making light-resists including pinhole photography”. It was available for sale for many years in a soft-cover spiral bound edition directly from the author, Sarah Van Keuren. Mrs. Van Keuren has decided that she no longer wants to maintain the book and deal with the printing and shipping, so she is making it available chapter by chapter for free to download on www.alternativephotography.com If you want a hard copy, you can contact the publisher of AlternativePhotography.com and see about remaining stock.