Contact frame glass

Discussion in 'Alternative Processes' started by Jim Fitzgerald, Jul 18, 2008.

  1. Jim Fitzgerald

    Jim Fitzgerald Member

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    I've made a contact printing frame to use for my 8x10 carbon printing and I have a question on the glass to use with the frame. Do I need to use a special tempered glass from a glass shop or can I use the stuff you get at Lowes? I will be using a 450 watt mercury vapor bulb about 18" from the frame and exposures could run 15-20 minutes? I'm going to have a fan on it to keep it cool but will the glass explode from the heat? I had another Alt printer tell me that I need special glass. Is this true? Thanks for the help.


    Jim
     
  2. RobertP

    RobertP Subscriber

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    Jim, I replaced my glass on my NuArc 26 1K with regular plate glass. Just make sure they don't sell you glass with UV blocker. Ask you friend, the alt printer, how long has he been doing alt processes, not counting today? My glass works fine under 1000 watts. I think sometimes people just try to make things way to complicated.
     
  3. Jan Pietrzak

    Jan Pietrzak Member

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    Jim,

    First of all, what size is the print frame. These are some of the things that I have used,
    For old 8x10 print frames some old glass plate negs (clean off the emulsion)

    No glass plates, use framers glass (non UV coated) take a piece of white matt board into the shop and check for coatings (put the matt board down and then the glass, cover only half the board, check for changes in color.)

    You can use regular window glass but it has other things in it. If the glass is to green or to yellow you will have problems.

    So look for the clearest glass you can find and that will work just fine,

    Hope this helps

    Jan Pietrzak

    The show is still up at Freestyle Photographic Supply
     
  4. Jim Fitzgerald

    Jim Fitzgerald Member

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    Jan, thanks. The size of the frame is 10x12. I will take your advice and check for color problems.
    I can't remember if I told you this but the image at Montana de Oro of the tree's is a great composition. I took one from about the same location with the 4x5 some time ago but could never get a decent print. Yours is great!

    Robert, it looks like the edges of the glass are green. I think my friend was talking about clear glass with no UV blockers in it. Guess I need to go to the glass shop.

    Jim
     
    Last edited by a moderator: Jul 18, 2008
  5. Curt

    Curt Subscriber

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    Jim, I bought a sheet of certified optically clear glass 13 x 15 inches and 1/4 inch thick with the certification for that sheet of glass from the Surplus Shed some time back. It's absolutely clear and flat, certifiably so. I use it for what contact printing I do. You might want to check them out.

    Curt
     
  6. bill schwab

    bill schwab Advertiser Advertiser

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    No need to find something special Jim. Most single weight glass that you will find in any hardware will do just fine as long as it is not UV blocking. Be sure to use a sharpening stone or some sort of emory cloth on the edges and corners to dull them from cutting you.
     
  7. Jim Fitzgerald

    Jim Fitzgerald Member

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    Curt, I'll check them out. Thanks for the source.

    Bill, I got some window glass from the local Lowes and it has the smooth green edges. I don't know if it is UV blocking or not. Does anyone know how to tell?

    Jim
     
  8. bill schwab

    bill schwab Advertiser Advertiser

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    Hi Jim,

    In most cases this will be specified in the description, "UV coated". I would think it more of a specialty item than might be found at Lowes, but I can't be sure of that. I guess the easiest way to tell would be to print something through it unless you have a UV meter.

    Hope this helps... Good luck!

    BTW- My Nuarc has the same green edges and the glass works fine.
     
  9. Jim Fitzgerald

    Jim Fitzgerald Member

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    Bill, thanks very much. I'll give it a try.

    By the way I'm loving the images you are posting in the gallery. I wish I could have come up your way to shoot. All of the images that have been posted look fantastic. Maybe next time.

    Jim
     
  10. bill schwab

    bill schwab Advertiser Advertiser

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    It would be great to have you up Jim! Please keep it in mind for next year. And THANKS for the kind comments on the work. Means a great deal.

    Best, Bill
     
  11. Murray@uptowngallery

    Murray@uptowngallery Member

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    glass

    I doubt any place other than a frame shop or full-service glass supplier would have UV filtering glass you might 'accidentally' receive.

    The architectural type is sold as laminated, and sold more for safety with secondary benefit of UV filtering (I think I had to tell the glass supplier when we put windows in our building what I wanted or guide their research because UV filtering wasn't a main concern in most of their installations). The laminate layer between the 2 lites of glass is what provides the UV filtering (about 99% but I can't tell you exactly what that means in spectral details off the top of my head, just that it compares to minimum 97% for conservation grade picture framing glass).

    Non-UV filtering, 'regular' float glass (like hardware store window glass and non-UVF picture framing glass has roughly 43% UV filtering (same problem here, I can't remember the spectral definition that gives the 43% meaning). The green tint as viewed from the side I is from iron in the 'normal' glass recipe. 'Water-white (possibly a trade name) is low iron glass.

    I cannot find a UV filtering spec for the non-conservation version of TruVue UltraClear (I think it's no longer sold, but the only product name I could remember). It can be hard to find UV filtering data for products not intended as UV filtering, but they all have varying degrees of it.

    I don't think there is an advantage to the low-iron glass for contact printing, especially if you find a variety that only comes in a conservation grade (high UV filtering).

    The green cast is annoying on some things, whites & pale colors, but most people only notice it when they're made aware of it, or are matching whites (mats and wall paint, etc. If it's that important we also compare mats under glass.) That isn't an indicator of UV filtering or transmission. UV filtering glass filters wavelengths shorter than 380 nm. UVF Acrylic starts at 400 nm (slightly higher into the blue-violet
    range).

    I was only able to find UV filtering/transmission information for non-conservation glazing for Tru-Vue glass and Ato-Haas acrylic. Tru-Vue may or may not even publish their non-conservation spectral data anymore...

    'regular' acrylic (phone conversation with Ato-Haas polymer chemist) doesn't have a 'spec' for UV filtering because that's not what it's sold for, and may vary from mfr to mfr, but a ballpark figure is 70% UV filtering (not guaranteed). Unfortunately it's wavelength cutoff is different (spectrogram curve is very different not easily compared to glass).

    But what I got from this was if I want maximum UV transmission, 'plain' glass was preferable to acrylic by a large margin, despite the apples vs oranges factor. Scratching is another deterrent. Not having found UV filtering (and implied transmission information) for 'waterwhite' glass, unsure where I can get it from my current suppliers, my belief the color cast negligible if any effect on UV transmission and the premium cost are reasons for me to not pursue low-iron/'waterwhite' glass for contact printing, especially alt-processes.

    Visually, some things that may help you identify whether glass has intended UV filtering (but not assure you).

    TruVue Conservation Clear has a UVF coating that can be seen if your eyesight cooperates, by looking at the reflection of a light bulb, then shift your focus from the lamp reflection to the glass surface, back & forth, while you slightly rock the glass. It's a rare and perceptive person who sees it without having it pointed out. If someone forgets to label the back of piece of framed artwork that required it with a Conservation Clear label, we check for the coating before automatically changing the glass unnecessarily. It's getting a little trickier for me to see as my eyes age, but I don't get 'false positives' I sometimes almost convince myself I'm looking at uncoated glass & try again. Once you eye is 'trained' its' easy to detect. I only know one customer since 1993 (an interior designer) who saw it on her own (& disliked the distracting character it imparted to reflections in her opinion).

    Last ditch test is to take a razor blade or Xacto blade (not a glass cutter!) & try to gently scratch both surfaces of the glass (at an edge so you don't render it unusable for framing. The UVF coating on TV Conservation Clear will scratch, and the uncoated side generally won't. Maybe if you try hard enough you could.

    DenGlas, probably no longer made, had a 'dip' coating that ran on the edges years ago. One would cut the edges off so they were not visible. I haven't seen enough of it to comment on it's reflectance or scratch properties.

    Laminated UVF glass is for all practical purposes (maybe one could measure a difference in reflectance due to 6 surfaces vs 2) as clear as ordinary glass, but the center laminate layer can be seen from the side.

    'Ordinary' vs UVF acrylic is indistinguishable to the eye. Can only be identified by trusting the factory paper coating's ID label (if not cut off when cut to size) or spectral testing.

    While we have had suppliers send us wrong acrylic (both upgrade and downgrade), someone would have to be careless to accidentally give you a premium UV filtering product when you want 'regular'. The cost difference helps keep them from making that error.

    Oh, TruVue's Anti-Reflective (AR) and Museum Glass have <1% reflectance compared to about 8% typical of most of their non-surface-treated (Perfect Vue Low Reflectance, if still made was about 4.6%), and AR used to be described at having 78% UVF (better than regular glass, but not a conservation product) and Museum has >97% UVF. If you move either around long enough while having a bright light source above or behind it, at certain angles you can see a pink or green reflection. (I have seen blue reflections in a local art museum but don't know whose glazing produt that is).

    Too much info? (Maybe it's good for something else some day).
     
    Last edited by a moderator: Jul 19, 2008
  12. Jan Pietrzak

    Jan Pietrzak Member

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    Jim,

    When you saw the show at Freestyle you can just pick out the 3 or 4 framed prints that are not behind UV glass. I had some older frames that are the same except for the glass. UV glass will have a slight pink/yellow cast to it if I had all the same frames you would not see it. After we hung the show I looked around the room and saw it I asked about it and other people could not see it.

    Thanks for you comments on Montana de Oro I have 10 negs of that image the fogg just kept changing.

    Jan Pietrzak
     
  13. Jim Fitzgerald

    Jim Fitzgerald Member

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    Bill, I'm going to have to mark my calendar for next year. I've never been up your way. It would be great.

    Murray.... You're making me crazy!!!! I thank you for the excellent response. Very complete and educational, thank you. It may take me a while to digest all of the info. I hope others read this great information.

    Jan, I will have to take a look the next time I'm at Freestyle. All of the work is great. I just instantly new the Montana de Oro image. Great place to work isn't it? Beautiful prints.

    So, I can figure that the regular glass I have for my frame will not crack and shatter into pieces under the UV light for 15 minutes? Is this correct? Thanks.

    Jim
     
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  15. Murray@uptowngallery

    Murray@uptowngallery Member

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    I don't know what how much/how fast temperature has to change to make glass break under heat, but suspect that other than Pyrex, Kimax, and that type that are made to tolerate large temperature changes (usually made as tubing & vessels/glassware for chemistry), sheet glass you can easily buy probably doesn't have any special thermal expansion properties...

    I could be wrong, but thought the advantage of tempered glass is that it breaks into very small pieces instead of large jagged pieces that could be more dangerous (car windows, for example).

    You raise an interesting concept - I have read posts from people who had an enlarger that broke internal sheet glass while illuminated for a very long exposure. This puzzled me; the initial thermal shock of turning on the (incandescent) lamp would seem to be the worst change. Even if the temperature got a lot higher over several minutes, I would think it would be more gradual than that initial temperature change.

    Maybe it broke because it was constrained in such a manner that a long exposure created a large amount of thermal expansion, stressing the glass as it began to expand against the mounting hardware or frame.

    It would seem to be a good idea to make sure the glass has enough room to expand freely and not exert pressure against its constraints. I guess this is relevant to thickness as well as length and width (I really do mean guess).
     
  16. Dan Dozer

    Dan Dozer Subscriber

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    Hi Jim,

    Getting in on this a little late and don't know if you'll check this or not. I have used the absolute cheapest glass I could find (very thin stuff from Home Depot) and have no problems at all other than the fact that it does flex a little due to it's thickness (or lack of). However, even so, it still seems to work fine on the 8 x 20 printing frame I made. I have also tried some thicker glass from the local glass shop (called double strength) and it performs just like the Home Depot stuff. My commercial 11 x 14 split back frame has glass thicker still (close to about 3/16" thick) and I see no real difference between the three glass types/thicknesses.

    So - is carbon becoming a reality yet?
     
  17. Jim Fitzgerald

    Jim Fitzgerald Member

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    Dan, thanks for the input. I built a frame for my 8x10 negatives. It is a 10x12 frame and I put in some home made pin registration. I used some glass I got from Lowes and it worked ok during my 1/2 hour test with my UV light. The fan I used kept things cool.

    I hope to try multi-layered carbon prints eventually. I have my UV light ready to go. I've been really sick the last week and did not have the energy to do any thing. I may try to pour some carbon tissue this weekend and then get to printing soon.

    Jim
     
    Last edited by a moderator: Jul 27, 2008
  18. tim rudman

    tim rudman Member

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    Hi Jan, long time no see.
    Congratulations on the show at Freestyle. I wish I could see it. I looked it up on the site but sadly no images.
    best wishes
    Tim
     
  19. Jim Fitzgerald

    Jim Fitzgerald Member

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    Tim, the images are really beautiful. It goes to show you that they do not have to be big to be beautiful. Jan's work is really inspiring. Next time I'm in I'll take a look for you!

    Jim
     
  20. tim rudman

    tim rudman Member

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    Oh thanks :wink: That's alright then. Tell me if I enjoyed them :smile: (I knew I would)
    Tim
     
  21. Jan Pietrzak

    Jan Pietrzak Member

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    Tim, and Jim

    Thank you both for your kind words, the show was fun. Sorry Jim that I am stealing your thread. But these are contact prints made with glass on top.

    Jan Pietrzak
     
  22. Jim Fitzgerald

    Jim Fitzgerald Member

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    Jan, you and Tim can steal my thread any time you like. It will just cost both of you guys some of your fine prints!! Tim, the toning book is a work of art. Jan I was at Freestyle again..... love your work!

    Jim
     
  23. tim rudman

    tim rudman Member

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    Thank you Jim :smile:
    I didn't mean to steal your thread. I'm sorry :smile:
    Tim
     
  24. Jim Graves

    Jim Graves Member

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    Glass or Plastic for alt. proc. contact printer

    I recently got a really good deal on a very nice 11x14 contact printing frame ... of course, when it arrived, the glass was shattered. I've heard that regular window glass, as well as being pretty thin, filters a high % of UV.

    Any suggestions on glass type or plastic alternative to fix it? Thanks
     
  25. Trevor Crone

    Trevor Crone Member

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    Jim,
    There is a thread in the Contact Printing section that has a great deal of information on the type of glass suitable for contact printing. http://www.apug.org/forums/forum55/52422-contact-frame-glass.html

    With regard to using plastic, personally I would not recommend it for the reason that it is liable to buckle under the changes of temerature of the printing light. Although this will of course depend on the wattage of your lamp(s) and the duration under your light source. Plastic also scratches easily and is prone to static charge which could attract more dust etc.

    Good luck,
    Trevor.
     
  26. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    Also, many plastics have a built-in UV blocker to prevent them from yellowing with exposure to the sun. So they're even more likely to absorb the needed UV for your process.