Over-heating causes Azo blacks to turn light brown?

Discussion in 'Contact Printing' started by kwmullet, Jan 8, 2005.

  1. kwmullet

    kwmullet Subscriber

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    Hey,

    I wanted to make a shadowgram of the filter drawer in my enlarger so I can match it up with gel filters, and .. well... I had only a handful of MG IV that I needed to use on a project but 3/4 of a box of Azo, so I used a sheet of Azo grade 2 8x10. Developed it in Ansco 130, "stopped" in a water bath, and fixed for about 3 minutes in TF-4, followed by an overnight static water wash, hanging to dry, soaking in pakasol and running through my glazing dryer to see how even of a gloss I could get.

    It came out with a slight curl, so I stuck the print between a couple of sheets of release paper, clothes-ironed it on high, put a couple of sheets of glass and ten pounds of weight on top and waited for it to cool.

    Not that the quality of a shadowgram is anything worth typing about, but if the problem here is something I'm likely to run into on important Azo prints, I'd like to know now.

    What was a solid, very dark black "background", had now turned to a cloudy pattern varying between a slightly lighter black and an almost zone V chocolate brown.

    Any ideas what caused this?

    - insufficient fixing in TF-4? The bottle recommends 1 minute for FB, I usually do 2 just to be sure. It was brand new TF-4 and none of the MG IV prints have shown any problems. Is there a paper equiv to the "double the clearing time for a film leader" test to see how long it takes a particular paper to fix in a given fixer?

    - some weird reaction of a chloride paper to too much heat?

    any help appreciated. This is weird.

    -KwM-
     
  2. Michael A. Smith

    Michael A. Smith Subscriber

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    My guess, and it is only a guess, is that your print was not washed--a static wash will not do it-you need changes of water--and then the heat got to it affecting the unevenly washed print.

    Michael A. Smith
     
  3. kwmullet

    kwmullet Subscriber

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    Thanks for chiming in Michael. Your "only a guess"es are as good as most people's long-determined, exacting research.

    Sounds like that might be it. I don't want to 'spend' any more sheets of Azo trying to experiment and find out. It's interesting that the effect didn't show up after running a lap on my glazing dryer. I expect that applied more heat than my iron. Maybe it was a delayed effect, and even if I hadn't ironed the print, it would have happened.

    I think maybe I'm overestimating the amount by which using an Alkaline tray line will reduce my wash times.

    Knocking on wood, hoping it doesn't happen on any subsequent real prints,

    -KwM-
     
  4. Alex Hawley

    Alex Hawley Member

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    It could have also been too much heat from the iron. I found I only needed a low setting, maybe about 200F or a little less, to flatten my prints.
     
  5. kwmullet

    kwmullet Subscriber

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    how about mounting? I've got a 1200w iron using US current. I've been using high setting, ironing through release paper and just guestimating how much time to iron the assemblage.

    I've got a piece of cut granite qeued up at a local vendor to be cut, so one of these days, I'll be switching to heating that in the oven and using that as my poor man's dry mount press.
     
  6. Francesco

    Francesco Member

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    Using an iron on valuable prints is simply too risky because it is nearly impossible to apply the heat evenly at one time, something a dry mount press will do very well indeed (as well as even constant pressure). In addition, when using a dry mount press one can sandwich the print and board in between two other boards so that the print never touches any heated metal surface. I dry mount this way using 300 deg F and have yet to see any discolouration or staining or any other strange markings.
     
  7. kwmullet

    kwmullet Subscriber

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    Nice when you've got one, Francesco. If someone's paying me for a job, I'll take it to the frame shop in town. Otherwise, I can't afford to either have someone else do it or buy a dry mount press. One of these days...

    A lot of other folks are in the same boat, judging from the volume of archives on make-do dry mounting.

    -KwM-
     
  8. Alex Hawley

    Alex Hawley Member

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    I was in the same boat until last week. I bought an old used press from Brian McGuiness and its a Godsend. How I did without I'll never understand. New ones are expensive but a goo old one can be found for a reasonable price.
     
  9. kwmullet

    kwmullet Subscriber

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    certainly on my list. Next time I've got US$100-130 disposable money, I'm getting a Thomas Duplex safelight. Next time I've got US$250-350, I'm getting a dry mount press. Next time I've got around US$500, I'm going shopping for a speed graphic (already have a crown) body with a side Kalart rangefinder and an old, shutterless portrait lens and one or two more grafmatics, if there's any surplus.

    For now... it's clothes iron time while I'm waiting for my piece granite to be cut. :smile:
     
  10. noseoil

    noseoil Member

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    Granite should be a good working alternative to a press, but I have one cautionary note for its use. Since the adhesive will flow under heat, too much heat or too much time can cause a "starved joint" between the backing and print. Sorry for the woodworking lingo, but this is what we called it when enough glue was applied, but it didn't end up where it was needed. If the glue becomes too liquid, it will soak into the fiber surfaces, like a sponge, and not leave enough behind for the bonding between them.

    Do a couple of experiments to determine temperature and time needed for a good bond and "stick" with these numbers. Use the same thickness of mat for your press each time, control all factors consistently and things should go well.
     
  11. kwmullet

    kwmullet Subscriber

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    good cautionary note. During the recent postcard exchange, during which I was clothes iron mounting all the card, I had to unmount or toss a few because I heated them TOO much and for some reason lost the effectiveness of the dry mount tissue. From what you say now, it makes perfect sense that the glue got wicked into the print and the backing material, to which I give an anti-archival "Yech!" :smile:

    -KwM-
     
  12. noseoil

    noseoil Member

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    The first time I tried my "new" press on an RC color print, it was just a little too hot for the surface of the print. I cooked a nice 11x14 image enough to melt the surface and pick up materials from the mat on front. Live & learn.

    I found an old Seal press on ebay which included tissue, tacking iron and the press itself for about $300. It won't quite cover a 16 x 20 in one pass, but will in sections. The pad and platten were in excellent shape. I had to replace a switch and tighten things up a bit, but it works like a champ now. I'm running at about 190f and it does a great job on azo or any other fb paper.