I think that you would not experience quality issues if you were contact printing negatives exposed in camera. I had one client that I copied fine art drawings for. I made same size camera negatives on 30" x 40" Plus X Pan film and then made contact prints. The quality was outstanding. I have also made large size duplicate negatives from smaller format film for either enlarging or contact printing. Unfortunately the variety of films available today is very restricted with a corresponding reduction in the options available for reproduction. I guess at one time I had at least twenty BW films in my shop to choose from and many choices available for procedure.
padraigm, I apparently live in a world with different physical laws than everyone else.
I started platinum printing trying to use an 11x14 contact printing frame and could never get tight enough contact until I started jamming pieces of card behind my paper to force it to be tighter. I finally gave up when I started getting little wood chips to deal with.
I decided to just use 1/4" plate glass, two sheets. I found I needed clamps to really get it tight. The glass was 11x14.
Then I started printing on 11x14 paper and needed oversized glass. I tried 16x20 glass with 4 clamps and could never get it tight enough. I tried foam behind the paper and card or mat board behind the paper and could not get it to work. Very small areas would be out of focus. So I got glass cut 14x18 and started using 8 small size industrial clamps. 3 on each side and 1 on each end. Now I get tight registration. I have never seen any newton rings.
Awhile back I was hired to print some antique 11x14 glass negs in platinum. I needed over size paper to print on so I went back to the 16x20 glass and sandwiched the 11x14 glass negs between 2 sheets. A couple of the glass negs were not perfectly flat and some small areas printed a little soft.. I should have gotten a vacuum easel.
Perhaps you should consider a vacuum easel. You can make one pretty easily.
I have a frame that comforatble holds 11x14 negatives. It came out of a mid 70's plate burner.
It has glass plates on both sides of the frame , and has a piece of black 'velvet' bonded to both sides of some kind of cardboard board that sits between the glass panes.
Originally the frame was hinged mid long edge to swing in the middle on a support so that you could load one side, then flip over and load the other side. I guess you flipped it while the burner was on so as to do two burns for one start of the arc lamp.
The velvet is stiff to crush, and keeps the sensitized paper in good contact with the negative up against the glass.
I have yet to use it by loading two sides at once.
Thank you so much everyone for your input. At the moment I am limited to 8x10 and happy so far with the contact frame I have. Looking to go bigger especially with some pan shots and will be dipping my toes in digital negs soon. It seems there are some who get good prints with bigger contact frames and others that don't. I think I will try Dennis solution with clamps first while keeping my eye out of a vacuum frame.
Again the input has been invaluable, thank you again
Will insufficient pressure from the glass on the negative and paper cause Newton rings? I am going to take a shot at 20 x 24 inch contact prints, and I want to be sure that I set up in such a way that I do not have a problem with Newton rings. It appears from your post that anti Newton ring glass is unnecessary. In fact, it seems to me that I have read posts from individuals that encounter problems with Newton rings in making enlargements despite their investments in anti Newton glass.
Originally Posted by dpurdy
I'm making a crude 17x17 frame, i'll let you know how well it goes! :D
Best of luck. Please keep me posted.