Originally Posted by dustym
As you can probably imagine the equipment needed for contact printing can be as minimal as you'd like. Edward Weston made absolutely wonderful prints with a simple contact print frame and bare light bulb. IMO the main obstacle in contact printing of any size negative--and, the larger they get the greater the pain--is trying to achieve good contact between the negative and glass. Any minute pockets of air space, refraction within the glass itself, etc, can and will cause Newton's rings. This can be a MAJOR pain to resolve!
FWIW, I've read comments that a thinner piece of glass is better than, say, plate glass because of refraction characteristics of the glass itself. Others say to use plate glass because you'll get better contact. Many years ago Ron Wisner and I embarked on a "mission" to resolve issues with Newton's rings that I experienced with nearly every print. Our (mostly Ron's) solution was to single coat one side of a 9x12 piece of plate glass--this was the same coating used for lenses--to bring the transmission properties of the glass closer to 100% and to eliminate as much reflection/refraction within the glass itself as much as possible. It worked great! At first, I printed images (8x10) of mine that I'd had trouble with before...no Newton's rings. After a couple of weeks, I decided to get really sinister and contact print a neutral gray target. I can't imagine a worse scenario for testing of contact printing! I found a couple of very minor issues, but nothing that would cause concern in normal printing. Didn't mean to bore you with this story...rather simply trying to pass on some thoughts about how "simple" contact printing can be!
BTW, I do all my contact printing using an enlarger as the light source; makes for better control, IMO.
Good luck as you move forward with your own contact printing. And, welcome to a wonderful world...if you've never experienced a contact print of your own work you're in for a real treat! Enjoy!!