Good Afternoon, Hoffy,
HenrySamson has it exactly right. 1/4 inch glass is preferable because its weight helps flatten negatives, and it's less likely to break than the 1/8 inch stuff. Mine is also oversized at around 11 x 14, a bit larger than Henry's, mostly to increase the weight slightly.
Thanks for all the comments and replies. I will go for the 6.5mm glass and take it from there.
alright this topic seems to have answered a question I had and raised a few more.
I have an 11x14 contact frame, Century made and it needs glass. Based on this discussion I should get antiglare and thicker than 2mm. For this contact frame, how thick should my glass be? I understand that some of you are using super thick glass which has the weight enough and eventually I will probably go that route but I have a gadget and I want to use it! ;-)
77seriesiii, ordinary 2mm glass will do the job for your 11x14" contact printing frame. I have one from Bostick and Sullivan (same size as yours, actually oversized for allowing brushmarks and white space around the image) and use it for different alternative processes w/o troubles. I broke its glass twice before, and I just replaced it with ordinary glass from glass shop w/o any adverse effects. (Have them file - if that's the correct term for glass - the edges and corners to eliminate the risk of self harm while handling it!) I always pay attention to keep a spare glass in case of an accident... I sometimes see Newton rings, but they don't seem to register in the prints. (Maybe UV light - which is what I use for exposures - is less affected from newton rings...)
I use the same glass, mine just cracked the other day so I was wondering if I needed something different. I have seen newton rings in the glass as I move around the frame and like you they havent registered. Also, like you, I am using other processes, right now I am trying to print consistently with vandyke browns, so far no two prints are alike. One day, I'll nail it.
By just using the weight of the glass how do you go about looking at your print without losing registration like you would with a split frame back ?
I use one with POP processes and often enough with DOP also as there can be some hints in the initially exposed paper (solarization around the film edges for instance).
I am a contact printer who just uses the glass but I am printing on photographic paper so there is no need to inspect (nothing to see anyway). I would not think that using just glass, as opposed to a split frame, will be suitable for processes such as POP paper or platinum or any of the other processes that require inspection.
Originally Posted by nick mulder
use scanner glass
How about use a scanner glass? I have a few scanners or those multiple function printers all with glasses. Are they better for the contact printing purpose because they are actually designed with image copy/scan in mind?
Applies to UV processes only: Scanner glass will do the job IF it's indeed glass! ;) All the flatbed scanners I've used (and seen) were fixed with acrylic lids and AFAIK acrylic isn't as transparent to UV as ordinary glass...
OTOH, even if your process doesn't need UV light, be warned about the fact that acrylic is way lighter than glass, therefore you'll loose some pressure which may translate as unsharp contact prints...
Reviving an old thread...
Originally Posted by Loris Medici
I think the opposite is true about acrylic transmission of UV. See here.. http://www.fresneltech.com/materials.html
Making an acrylic (plexiglass) or polycarbonate contact printer would be great for alt processes. Since it's lighter though, I wonder what thickness one would need to provide substantial weight for holding things flat, and if that increase in thickness would negate the boost in UV transmittance (I suspect it wouldn't). Or alternatively, if you designed a printer with even pressure around the edges you could probably get around any issues from the weight difference, but rigidity would become just as much of a problem.
update: something like this -> http://www.spartech.com/polycast/solacryl.html