Does the thickness of a proofer's glass affect the quality?

[DanielStone]

hey all,

i have a pretty simple question, but one that has been nagging me for a month or so.

Problem: I have been looking to make myself a proofer, basically one that is similar to one I've seen at some commercial pro labs. It is similar to the one at this link, the 3rd from the end (on the far right side of the page)

http://www.richardnicholson.com/darkroom/

the one i'm referring to is in the picture titled "tom smedley, metro, soho"

My construction materials was going to be a 1-1.5" thick block of butt-jointed and glued hardwoord, most likely scrap maple or oak, being planed-down to a nice even, smooth block of wood roughly 13"x16".

But my main question is this: I need some heavy glass. I have talked with my local glazier, and because I do color work as well as b/w, he recommended something in the neighborhood of 3/8" thick, and going with the "starphire" glass, since it has a lower lead content or something like that, which in turn has less of a green cast, actually, not really any that i could see.

Have any of you run into this problem before? Its just that i want to make perfectly sharp contact sheets/prints, and since I'm in the process of remaking ALL of my contact sheets that I proofed in printfile sleeves over the last year or so (150 odd rolls of b/w and color 135/120/220) and 100+ sheets of 4x5/8x10.

its a task I've decided to do, and so far, its been a slow process, being that my budget as a student is quite limited right now with fall registration starting in a couple of days.

any insight from you wise fellows out there would be appreciated.

my goal is to stay under 60-70 dollars, as the woodworking would be done by myself and a friend(who has the planer and woodworking equipment).

thanks,

dan

 

[DanielStone]

note to add:

this is what I plan to be the last proofer I will even need to buy/ need ever again, period.

I am also going to incorporate some threaded feet into the bottom with rubber ends, so depending on where I'm printing(school, or eventually at my home darkroom, which will be a few years down the road at this point, since I'm 21 ) it can stay level, and not get rocked around, even if I might bump it slightly. i've tried taping things down to the baseboard/counter, and frankly, IMO, its the worst way. I just prefer something damned heavy.

 

[glbeas]

Sounds like you are going in the right direction. The thicker glass is also needed to prevent flexing when the edges are clamped down for added pressure. A material with a slight give on the base is good to allow the pressure to be more even. My contact frame uses felt on the pressure blocks. Perhaps a sheet cut to fit but not glued down would be best so you have the option of proofing with or without it.

 

[Monophoto]

My proofer is a DIY model - a sheet of plywood with rubber feet on the bottom, and felt glued to the working surface. I attached a sheet of glass using duct tape (of course) - two strips on opposite sides of the glass to form a tail that I stapled to the edge of the plywood.

The glass I chose to use is automotive safety glass. At the time, that decision made sense in terms of safety, but it proved to be a bear to actually cut since safety glass is actually two sheets of glass joined together by a layer of some kind of plastic - it's necessary to score both sides very deeply and then gently break the glass. Finally, I had to use a utility knife to cut the plastic layer. In retrospect, I think I would have been better off with ordinary window glass.

Bottom line - I made that proofer in 1978 and it's still working just fine. So, yes - it was the last proofer I will even need to buy/ need ever again, period. The only aging consideration - the rubber feet have hardened over the years with the result that they do slide a bit more than they should.

 

[David A. Goldfarb]

The glass isn't in the image path, so it can be quite thick. You can also make the proofer oversized so that the glass will be even heavier. I proofed with an 11x14" sheet of glass straight on the enlarger baseboard for years.

I wasn't sure about your plan from your post, but don't proof in any kind of sleeve if you want really sharp proofs. If the film and paper aren't emulsion to emulsion, you can't judge sharpness from a contact sheet.

 

[Nicholas Lindan]

If your goal is 'perfectly sharp contacts', I think you may be disappointed with this style of proofer - where the weight of the glass supplies the contact pressure.

Glass and gravity simply won't give enough pressure to keep things in tight contact. Starphire is a low density soda-lime glass, 2.5 gm/cm^3. If your proofer is 9x12" x 3/8" the glass will weigh about 3 1/2 lbs. The pressure would be 0.5 oz/sq inch. Going to the heaviest flint glass would only increase the pressure to 1.5 oz/sq in.

For this style of proofer you will need to have a very light foam blanket as a backing surface. There is no need to have a perfectly flat surface under the glass, nor is there any need for any strength. The proofer in the illustration looks like it has a clamp on it in an attempt to increase the contact pressure.

Precision contacting systems draw a vacuum between a rubber mat and the glass. Atmospheric air pressure clamps the materials together at 14 lbs/sq in, or a total clamping force of 1,500 lbs. And this can be done with thin glass and a sheet of rubber...

Look for vacuum contacting frames on Craigslist and ebay and call around to some local print shops. With the printing industry going digital the old contacting frames are now surplus and often end up in dumpsters.

Most of these are large - 24" x 36" is considered a small one. However, if you plan on contacting a large number of rolls you can now do several rolls as once. You can cover the vacuum frame with a sheet of cardboard and use it as a table when not printing.