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  1. #11
    Vaughn's Avatar
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    Quote Originally Posted by holmburgers View Post
    Ahhh! Don't tease us!

    Here.... crack your back in different place and maybe it'll come "flashing" back to you...
    How I wish it was that easy to revive old brain cells!LOL!
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  2. #12

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    Regarding the correlation btw dichromate and contrast:

    Adding more dichromate sensitizes the tissue/emulsion more so that exposure is hardening more of the zones in your negative. Less floats away in the clearing stage. There is less difference btw the shadows and the highlights.

    Less dichromate equals less sensitivity, so your exposure is hardening mostly the clearer areas of your negative (the print's shadows), the rest floats off. Hence, you're left with exposed shadows and less exposed midtones and highlights, a higher contrast print.

    I come at this from a gum dichromate experience but its effect is the same. I might add that this is only one variable in a hugely multi-variable process, both gum and carbon.

  3. #13
    Vlad Soare's Avatar
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    Thanks, guys.
    I've got my first carbon print today!
    OK, it isn't something to write home about, but at least it's a clearly defined image. I was very sloppy because I only wanted to see if and how the process works. I was only after an image, any kind of image. I figured I'd deal with quality issues later.
    I had a lot of bubbles due to not letting the glop sit long enough before pouring it on the support. Also, although highlights look quite well, and midtones show very fine details, shadows are light gray. There's no real black. Not even the areas that weren't covered by the negative are black. I'm not sure whether this was due to not enough pigment in the glop, or not enough exposure, or both.

    The sensitizing was done by immersing the tissue in a 3% potassium dichromate solution for three minutes with constant agitation. The exposure was twenty minutes (it was about twice the time I use with cyanotypes and vandyke prints).

    Now I'm going to start standardizing my workflow. I'll measure the water, gelatin and pigment accurately, I'll take careful notes of every step, I'll let the glop sit at least two hours before coating the support, and will mask the edges of the negative. The next print will hopefully be much better.
    I'll keep you posted on my progress.

  4. #14
    paul_c5x4's Avatar
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    I started with a 2% potassium dichromate solution, but recently dropped to 1% (five minute soak) as a result of this thread. My whites are still white, but the blacks are darker with the neg edges being really black. If I get time over the weekend, going to try a 0.75% or even 0.5% solution.

    You might want to post your glop recipe for comments from the experts.

  5. #15
    Vlad Soare's Avatar
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    I didn't use any recipe. I just found some watercolors that my daughters weren't using anymore, picked the black tube and squirted about half of it in a cup, mixed it with water and added it to the gelatin solution. The gelatin solution was approximately 10%. I say "approximately" because I had used a large beaker to measure the water (which is far from accurate) and I hadn't weigh the gelatin, but instead relied on the amount indicated on the package (which is probably just approximate). I also added 40g of white sugar.
    So it wasn't much of a recipe.

    Anyway, this time I'll make a real (that is, accurately measured) 10% gelatin solution. I've got some India ink, and I'm thinking of starting with 15g per liter.

    So, more questions:

    1. Could I just add the pigment to the liquefied gelatin solution while stirring? Or does it really have to be first mixed slowly with water, a few drops at a time?

    2. Would it help with the elimination of bubbles if I stirred the glop continuously during the two hours of sitting? I'm thinking of using a magnetic stirrer, the reasoning being that magnetic stirrers agitate the liquid from within, without introducing fresh air (plus, I could leave the stirrer running on low speed for as long as I wished). Would it help? Or would it be completely unnecessary? Do all bubbles go away by themselves simply by letting the glop sit for two hours?

    3. What do you think about the idea of using a sheet of scrap 8x10" film (the back, not the emulsion side) as a tissue base? I imagine it must be just perfect - resistant, thick and stiff enough not to curl, while also flexible enough to be handled comfortably. Any reason why it shouldn't work?

    Thank you.
    Last edited by Vlad Soare; 02-17-2011 at 12:38 PM. Click to view previous post history.

  6. #16
    Vaughn's Avatar
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    1 -- I put the watercolor pigment in a 35mm film can when I am weighing it, put in some warm water, cap it, and then shake it. Then I pour it directly into the melted gelatin while it is on the magnetic stirrer. I add more water to the film canister a few times to clean it out. The total amount of water used is measured. The last bit of water in the canister has alcohol added to it to help get rid of the bubbles.

    2 -- Unless your stirrer also has a heater, the glop will cool down and get too thick for the stirring rod to move. I use a water bath and occasionally put the jar on the stirrer -- then back in the water bath. The magnetic stirrer is great for stirring without adding air into the glop!

    3 -- It works, but since the tissue should be larger than the negative (about an inch in both directions so you can have a safe edge), 8x10 film as a tissue support won't work for an 8x10 negative/print. The only problem I had with using film as tissue base was getting the tissue and negative to stay in good contact during exposure (the film is pretty stiff). A better contact printing frame solved this. I normally use used litho film -- it is .004" thick instead of the usual .007' thickness of film.
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  7. #17
    Vlad Soare's Avatar
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    Thanks, Vaughn.
    I've read that the glop can be frozen and reused later. Does it really have to be frozen, I mean literally stored in a freezer? Will it go bad, or at least change its properties, if I keep it at room temperature?

  8. #18
    Vaughn's Avatar
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    I have had glop go bad in the refrigerator (mold) within a couple weeks. If it must be stored, I would add a preservative to it, such as thymol. I have never tried freezing glop.

    I think it would just be best to develop a work routine that allows one to pour tissues (using all the glop) as soon as it is possible after making the batch of glop. Then these issues are not a problem. The tissues are far more stable to store -- I have used tissues that have been kept out in the open for months...I just had to dust them off well before sensitizing!LOL!
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  9. #19
    holmburgers's Avatar
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    I've had some glop in my fridge for many, many months now and it doesn't stink or have mold. But, my fridge might be coler than Vaughn's, IDK. Like he said though, tissues last a lot longer, especially if cold. I believe Luis Nadeau says up to a year or more if fridged.
    If you are the big tree, we are the small axe

  10. #20
    Andrew O'Neill's Avatar
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    Because so many things can go wrong in this medium, it is wise to be accurate and consistent during all phases of the process.
    When I mix up my glop, the sugar goes in (50g), followed by pigment (lampblack)
    6g. First, I pour some of the melted gelatin into the pigment which is in a small cup and mix thoroughly. Then it gets poured into glop and stirred. I found if I dissolve all the pigment first in gelatin, there won't be any sitting on the bottom of pitcher. 70ml % isopropyl mixed in. Then it all gets filtered through a pair of ancient underwear into 500ml plastic bottles, placed in hot water to gas out, and Bob's yer uncle! If there are bubbles sitting at the top after filtering (and there usually are quite a few), they get spritzed with isopropyl alcohol.

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