Alternative Processes: Some of the "daylight" processes like SelectaColor, FA-1 sensitizer, blueprint and platinotype, require a full-size negative for contact-printing. I'd like to make such a negative from a color print. How do I go about it?
Formerly, full size negative transparencies could only be made photographically, but now can be made digitally with any inkjet or laser printer, or photo-copier.
Start with any kind of original-- a black & white print, color print, black&white negative, color negative, black&white or color slide, digital photograph, or an illustration taken from a book or magazine. You can also start with a drawing or a solid object like a leaf (popular with beginners.)
If you have a scanner or a digital camera, you can scan the image and reverse it to make a black & white negative image, then print this onto transparency material with a printer or copier.
If you don't have access to a scanner, you can order a transparency from your artwork at an office-service store like OfficeMax or Kinko's.
You may prefer to make a full-size negative the traditional way-- photographically, by enlarging onto black-and-white litho film. If the litho film is a high-contrast type like Kodalith, for a full tonal range develop it in paper-developer like weak Dektol instead of the high-contrast Kodalith developer.
You can also make your own "litho film" by coating Liquid Light or Ag-Plus emulsion onto glass or clear acrylic.
What is the sensitivity of the room light processes?
Each process has different sensitivities, the FA-1 being the fastest and SelectaColor the slowest, but in general the closer you get to the spectrum of sunlight, the shorter the exposure will be. Next to sunlight itself, the fastest exposures are in order with mercury vapor lamp, sunlamp, arc light, blue photofloods, daylight florescents, UV fluorescents, etc. With SelectaColor, they will give an image in about 10 minutes or less at 10 inches distance. Slower than these sources are cool-white fluorescents and quartz halogen (bare bulb), that will take about 30 minutes to expose SelectaColor with less time for the other room light processes.