Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,840   Posts: 1,582,573   Online: 969
      
Page 1 of 2 12 LastLast
Results 1 to 10 of 16
  1. #1
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,423
    Images
    2

    Acquired Cache of Agfa Copyproof - CPTA, CPTNa papers & CP 294b chemistry - ??

    Last night I picked up a new camera, and with it came a couple boxes of Agfa Graphic Copyproof papers. I had no idea what these were, and still don't exactly, but it sounds like some kind of diffusion transfer process.

    I received 2 boxes of CPTA - TONE PAPER, ANTIQUE and 2 boxes of CPTNa - CONTINUOUS TONE NEGATIVE PAPER, ANTIQUE.

    Also, I have five 2.5L bottles of CP 294b chemistry.

    The CPTA says "not sensitive to light" and the CPTNa requires a red safe-light.

    What do you know about these products? What does "antique" mean? What the heck should I do with it?

    thanks!
    If you are the big tree, we are the small axe

  2. #2
    Mike Wilde's Avatar
    Join Date
    Aug 2006
    Location
    Misissauaga Canada
    Shooter
    Multi Format
    Posts
    2,939
    Images
    29
    There was a graphics arts shop process I think was called PMT (photo mechanical transfer?) where you contacted one sheet with another, and fed it though a roller processor type machine with some kind of wet solution on one of the rollers, that took one sheet's image and transferred it to the other without the need for an enlarger or contact/ light source.

    There were papers that gave a positive from a positive, and more conventional papers that gave a negative from a positive. Some of them were not sensitized. Some were lith, some were continuous tone. I have not figured out what the chemical reaction was, but I am guessing physical development.

    I have a pal that has a stash in his basement of this stuff, and an open invite to come over and play with it, but time to visit him has been short as of lately in my busy life.
    my real name, imagine that.

  3. #3

    Join Date
    Aug 2003
    Location
    New York
    Posts
    110
    The CPTA will give you a "Sepia" color print which is why it's called antique. The paper called CPTN is a continuous tone style material used to make copies of photographs for paste up and was never capable of producing a display quality print. I still have some here along with the processor. CPN would be a step on a step wedge paste up copy for text and solid color. The problem I think you're going to encounter is the chemistry. It's shelf life was well, short. Considering this stuff has been out of production I believe for 10 years I wouldn't get my hopes too high. But if it does you would expose the light sensitive half in a process camera the sandwhich the two together running them through the processor, wait 30-60 seconds and peal them apart like a Polaroid. I was once told that AGFA actually owned the Patent on Polaroids diffusion transfer process and funded money to them for their suit against Kodak, but I guess only Kodak, AGFA and Polaroid would know if that's true.

  4. #4
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,423
    Images
    2
    Ok, so the CPTN is "more-or-less" a regular black & white paper, or at least, can I treat it like that to make interesting prints? As for the CPTA, what exactly is its composition? I wonder if there is something useful I can do with it.

    Is the "master" destroyed in the copying, or a better question might be, how many copies can you make?

    It's news to me that systems like this even existed; I wonder what the previous owner did with it.

    Hmm, what to do with the 3 gallons of chemistry though...

    Thanks guys!
    If you are the big tree, we are the small axe

  5. #5
    Mike Wilde's Avatar
    Join Date
    Aug 2006
    Location
    Misissauaga Canada
    Shooter
    Multi Format
    Posts
    2,939
    Images
    29
    I think the chemistry was lots of accelerator and hydroquinone. Short on any restrainer for the lith version. Try to tap off 500mL , and see if it will develop b&w paper; add in say 6g of hydroquinone needles or 100mL of striaght dektol if you don't have raw HQ.

    See how the paper develops, progressing from flashed paper (will it go black?), to paper exposed under a step wedge.
    Reading the log densities of the step wedge will give you an idea of the gamma of the developer for the time you used.

    You may have the base of a lifetime supply of accelerator for A+B developer if the original developing agent is pooched off, so think pyro, etc.

    If it is alkaline enough, then you may have the makings of a lifetime supply of lithographic A+B by just mixing in concentrated developing agent.
    my real name, imagine that.

  6. #6
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,423
    Images
    2
    Mike, this sounds intriguing, but I admit I'm not up on lith developing or why/how it works. Could you elaborate a bit more? I like the idea of having an alternate use for it.
    If you are the big tree, we are the small axe

  7. #7
    Mike Wilde's Avatar
    Join Date
    Aug 2006
    Location
    Misissauaga Canada
    Shooter
    Multi Format
    Posts
    2,939
    Images
    29
    Lith film developers are high pH (sometimes Sodium Hydroxide as the B - wear gloves), and high on the developing agent and moderate on restrainer agents like sulfite and bromide.

    Many are A - the developing agent, sulfite reservative and restrainer, and B- the accelerator

    D-85 is an exception. It is one solution, but finding the formaldehyde form in flakes is a challenge:

    Kodalith developer for lith film
    Water, not over 90F/32C 500 ml
    Sodium Sulfite (anhydrous) 30 g - quite low for a film developer
    Paraformaldeyhde 7.5 g - a preservative (dry form of formaldehyde) since sulfite is low, I think
    Sodium Bisulfite 2.2 g - sets a pH as the accelerator
    Boric Acid (granular) 7.5 g - may buffer with the bisulfuite to keep the pH stable
    Hydroquinone 22.5 g - this is a lot of developing agent per litre
    Potassium Bromide 1.6 g - this is quite small relative to the amount of develioping agent
    Cold water to make 1L

    Mixing instructions: Add chemicals in specified sequence. When mixing, seal the bottle to exclude air as each chemical is added. Allow to stand for 2 hours after mixing. Cool to 68F/20C for use. Store any unused solution in a smaller bottle, or use an amber bottle with glass marbles to exclude as much air as possible.

    Dilution: Use undiluted for maximum density.

    Starting point development time: 2 mins.

    More common A+B is D-8 Kodalith type developer, made up in two parts so the B does not kill off the A before being used on film

    D-8

    Part A
    Water 125F 750ml
    Sodium Sulfite 90g
    Hydroquinone 45g
    Potassium Bromide 30.0g
    to 1L

    Part B
    Water 50F (this is important) 750mL
    Sodium hydroxide 37.5g
    Water to make 1 liter

    Dilute 1 part A to 1 part B to 1 part water.
    Target time is about 2 minutes @68 degrees
    Contrast is very high.

    This developer will be dead in the tray in less than half an hour after mixing and dilution. Dilute in bits as you go.

    When compared to D-85, the actual working dilution of the HQ, and sulfite are similar; there is double the restrainer in D-8, so less 'infectious development' I believe is the term.


    Typically you tray develop orthochromatic high contrast graphic arts lith films to some extent by inspection under red safelight, which can be quite bright, compared to typical yellowish MG paper safelight filtration.

    Try out dim yellow as a safelight test; you may not need to worry about sourcing red filters if levels are low.

    My red filters are rubylith and supporting acetate cut to fit where the yellow filters usually go.

    I have a few hundred feet of Ortho Lith film in 35mm, and a fair number of 14x17 boxes of sheet film. EI6 is typically the daylight working speed. I treat it like enlarging paper as a staring point when making enlarged negs under the enlarger.
    my real name, imagine that.

  8. #8
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,423
    Images
    2
    So high pH, high developer concentration and low restrainer says to me "super active". Why does this result in high contrast and not just outright fog?

    Are exposures shorter if you're going to be lithing?
    If you are the big tree, we are the small axe

  9. #9
    Mike Wilde's Avatar
    Join Date
    Aug 2006
    Location
    Misissauaga Canada
    Shooter
    Multi Format
    Posts
    2,939
    Images
    29
    Fog needs time to build, these formulas can have dmax to 3.0 or more in less than 2 minutes.

    Lithing with film usually is done with a high contrast film, athough conventional films have such a high gamma with this stuff you might not know the difference.

    Exposure is a subjective thing. When I shoot lith film it in the camera I always bracket at least two half stops under and over. You never really can pre visualize the effect of where the white to black cut will occur when the high gamma slope will translate some 'shades of grey' things as clear, and others slightly lighter as black.

    Shooting slide dupes with lith film and develoepr can also be an interesting way to see how the scene can be abstracted in a different way, since some of the original scene range has been compressed already in the transparency.

    There is a mid 80's or maybe late 70's HP Photo book called 'High Contrast' by Elinor Steckler (I think that is the authors name) that gives all sorts of good lith film examples to fire your creative juices.
    my real name, imagine that.

  10. #10
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,423
    Images
    2
    I guess my exposure question was for the sake of comparing the characteristics of the developer, while minimzing variables.

    For instance, let's imagine we have a negative in our enlarger and we expose to prints for 10 seconds onto a b&w paper that can both "lith" & print "straight" well. Then put one in a paper developer and the other in a lith.

    Based off what little I know of developer chemistry, and what you've told me about lith developers, it seems that if this exposure produced a good straight print, the lith would be overexposed.

    But yes, I'm sure using a dedicated lith film changes things a bit as well. I'll look for that book next time I'm at la biblioteca.

    Thanks Mike
    If you are the big tree, we are the small axe

Page 1 of 2 12 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin