Carbon Transfer Questions

Discussion in 'Alternative Processes' started by Vlad Soare, Feb 15, 2011.

  1. Vlad Soare

    Vlad Soare Member

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    Hello,

    I'm just about to try my hand at carbon printing. For the time being I have just two questions, though I'll probably ask a lot more in the near future. :smile:

    1. The surface of my tissue, though dry, has remained a bit soft. The glop is flexible and has a slightly soft feel when I touch it with my finger. Besides, although yesterday, after I poured it, it had a perfect surface, after drying it exhibits a very slight "wavy" texture, plus a couple of pits which definitely weren't there yesterday. The temperature of the glop was about 30 or 31 degrees Centigrade (86-88 F) when I poured it. What happened? Was the layer of glop too thick? What makes a perfect surface turn into a not-so-perfect one while it dries?

    2. Sandy King's article states that "The contrast of a carbon image is controlled by matching the dichromate concentration of the sensitizer to the DR (density range) of the negatives: solutions high in dichromate are used for high contrast negatives; solutions low in dichromate for low contrast negatives.".
    Does this mean that adding more dichromate lowers the contrast of the print? This seems strange to me. Isn't it the other way around? :confused:

    Thank you.
     
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  2. Andrew O'Neill

    Andrew O'Neill Subscriber

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    If your tissue is a bit soft, then it is not completely dry. My tissue take a full 2 days to dry, and that's with a RH of 50%. What are you using for tissue support? What pigment? Is the pit from a bubble? Your pouring temp is probably okay. I consistently pour at 35C.
    Yes, adding more dichromate lowers contrast. It also makes the tissue more sensitive, so exposures are shorter.
    You should go to Sandy's yahoo forum and join up, as lots of carbon printers hang out there.

    http://tech.groups.yahoo.com/group/CarbronTransfer/messages
     
  3. Vlad Soare

    Vlad Soare Member

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    Oh, I see. I didn't think it can take so long for it to dry. OK then, I'll wait.

    I don't know exactly what pigment it is. It's some black watercolor I happened to find lying around. I'm going to get some India ink one of these days. The support is a sheet of clear plastic. I'll try a sheet of watercolor paper tonight and see how it works.

    That's strange. So, without dichromate the tissue is not sensitive to light, but if you use just enough dichromate for the tissue to be sensitive at all, then you immediately jump to the highest contrast possible? And then adding more and more sensitizer makes the contrast lower and lower? Well, it looks strange because I'm used to think about high contrast versus low contrast in terms of "deep blacks" versus "muddy blacks", and I expect more sensitizer to give deeper blacks, and less sensitizer to give weaker blacks. But I may be missing something.

    Thanks for the link.
     
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  4. Hexavalent

    Hexavalent Subscriber

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    Hi Vlad,

    I usually pour glop closer to 40 C, and let it cool slowly, without air drafts.
    Do you let your glop sit for a hour or two to allow trapped air to escape? A vacuum pump can greatly shorten this process - 5 minutes.
    A bit of alcohol in the glop helps with bubbles - use only pure ethanol or isopropyl (not cheap "rubbing alcohol" that may contain fragrance, colour etc.) I use yupo as my tissue backing, giving it a quick wipe with a barely damp cloth just before pouring the glop: scratches or dust on the surface can trap air, which subsequent shows upon dry-down. If you are adding glycerin to your glop, a very little goes a long way - it's easy to make never-dry tissue by adding too much :wink:
     
  5. Andrew O'Neill

    Andrew O'Neill Subscriber

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    For pigment I am using lampblack water colour paint. Sometimes I use India Ink, but I prefer the neutral tones of lampblack. The amount of pigment used will also have an affect on contrast.
    Don't use 99% isopropyl alcohol in the glop to get rid of micro-bubbles. Use 70%. If you use the stronger version, you will notice some of the pigment will congeil to the top. I
    l let the glop sit in hot water for about an hour before I pour.
    If I see any bubbles sitting on the top of the glop when pouring (I use a small glass beaker with measured amount of glop for each tissue), I spritz it with 70% isopropyl alcohol. If any bubbles appear on the tissue, I pop them with my finger. Some people use a rod to spread the glop around. I find this to be extremely messy and wasteful. Instead, I use my wife's comb. No glop wasted.
    How long does it take for your tissue to set after pouring? A long set time will result in uneven distribution of pigment. It will settle to the tissue support side.
    My room is 20C, so set time is about 5 minutes.
     
  6. holmburgers

    holmburgers Member

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    I oft have wondered about the concentration/contrast relationship.

    If you use 5% K-dich. then you are going to get low contrast. Perhaps this is because you have stepped over a critical point in sensitization, where your tissue is pushed onto a more "mellow"/straight section of the characteristic curve. With 2%, high contrast, the gelatin is just barely sensitized, so the points under your negative where no UV reaches are left w/ low exposure and low sensitization, thus very little hardening in those areas. In other words, there is a greater differential.

    I feel like I'm explaining this after getting a cavity and my mouth is numb, only it's my fingers and I'm typing.... what I'm trying to say is, I'm struggling to find the words! I'd like to hear someone's more intelligent thoughts on this phenomenon.
     
  7. Hexavalent

    Hexavalent Subscriber

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    If your pigment is settling, it is likely coarse, or not well dispersed. Working WC paint with a drop of photo-flo with a pallete knife on a glass plate, adding water a drop at a time helps dispersion. I have never experienced 'pigment settling' after thorough blending.
     
  8. paulie

    paulie Member

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    here is my list of probs and fixes.

    bubbles in tissue---use a hot rod to smoothe over the surface, using magnetic frame for glop
    streaks in picture---switch to tray sensitizing (easier and cheaper option)
    frilling ---shorten soak time and increase tissue area size and safe area
    developing streaks----larger safe area and lowered time and temp during dev
    low contrast--- use a lower dichromate concentration. (.5%-1%) is great for fibre quality negs.
    sticky tissue---lower sugar to 30g - litre (no need for clear plastic to protect neg)

    hope this helps

    paulie
     
  9. Vaughn

    Vaughn Subscriber

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    Someone (the late Gordon Chappel) once explained perfectly to me the relationship between dichromate dilution and contrast -- and as soon as I walked out his door and started down the road, it left me completely! Oh, well.

    I pour with the glop at 40C (plus or minus a couple degrees) in a cold (~16C) room. I pour directly onto plastic sheets -- moving the glop around with my finger tips to cover the plastic (actually used litho film). I wait perhaps 5 minutes, then tack the tissue onto cardboard and stand the cardboard vertically and have a fan blowing air (no heat) on it for the first 8 to 12 hours. This keeps the mold away. I wait for 48 hours (minimum) before printing. RH is usually around 60 to 70%. I get nice smooth surfaces.

    I use no glycerin (damp climate), and more sugar than most folks (8% -- 60grams/750ml of water).

    So many different ways to make good carbon prints. I use pigment concentration to control contrast -- as well as exposing/developing negs specifically for carbon printing. I have standardized on a stock solution of 8% Am dichromate, diluted 1:3 in acetone -- for a tissue for an 8x10 neg I use 5ml of the stock solution:15ml acetone. Not the "normal" way to work!

    I use 100% isopropyl alcohol -- I do occasionally get some gelatin congealing on top, but it readily melts back into the rest of the glop. Lately I have been adding the 100% isopropyl alcohol to equal amount of water (used to clean out the last of the pigment from the container I mix the pigment -- lampblack water color) before adding it to the glop.

    So many ways to make carbons! But pick one for awhile until you get a good grip on the process! best of luck!

    Vaughn

    PS -- I do not think "pigment settling" will be an issue -- the glop is too thick for the carbon particles to move significantly downward...especially once it starts to cool down (immediately after pouring). Just an opinion -- not based on any testing.
     
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  10. holmburgers

    holmburgers Member

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    Ahhh! Don't tease us!

    Here.... crack your back in different place and maybe it'll come "flashing" back to you...
     
  11. Vaughn

    Vaughn Subscriber

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    How I wish it was that easy to revive old brain cells!LOL!
     
  12. PVia

    PVia Member

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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.
     
  13. Vlad Soare

    Vlad Soare Member

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    Thanks, guys.
    I've got my first carbon print today! :D
    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. :smile:
     
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  15. paul_c5x4

    paul_c5x4 Subscriber

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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.
     
  16. Vlad Soare

    Vlad Soare Member

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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. :smile: :redface:

    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: :D

    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.
     
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  17. Vaughn

    Vaughn Subscriber

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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.
     
  18. Vlad Soare

    Vlad Soare Member

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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?
     
  19. Vaughn

    Vaughn Subscriber

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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!
     
  20. holmburgers

    holmburgers Member

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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.
     
  21. Andrew O'Neill

    Andrew O'Neill Subscriber

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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.
     
  22. Vaughn

    Vaughn Subscriber

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    I take no precautions regarding sanitizing my glassware, etc, I live in a place of constant high humidity, and work in a place that has a constant influx of people walking in and out (mold spores clinging onto air-born dust particles). Plus I refridgerated the glop after it already had been in a hot water bath for several hours. Probably the worse-case scenerio for working with such a great mold-growing medium of gelatin with a bunch of sugar in it!

    And it was the Art Department's fridge -- the secretary called me and asked if the jar of black stuff was possible mine -- it was stinking up the fridge!
     
  23. Vlad Soare

    Vlad Soare Member

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    Update:
    I left the glop in warm water for three hours, with occasional agitation on the magnetic stirrer. In the end there were just a few bubbles at the surface, which were removed with a teaspoon. So this time the tissue was perfect and dried with a smooth shiny surface, free from visible defects.
    So far, so good.

    I sensitized it with 3% potassium dichromate for three minutes and exposed it for twenty minutes. However, because I used a "normal" negative (that is, one developed for silver printing, which gives a straight print on grade 3), the 3% solution proved to be too strong. The exposure was also too long. What remained of the final image was too dark and very low in contrast. I'm saying "what remained of the image" because even after more than five minutes in hot water no gelatin came from underneath the tissue, so in the end I lost my patience and peeled the tissue forcefully. A little less than half of the image remained on the paper and continued to develop. I knew I shouldn't use force to peel the tissue from the paper, but by that time it was obvious that something was amiss and the print was going to be ruined anyway.

    I guess the tissue was so strongly overexposed that the gelatin hardened all the way to the support. Am I right?
    It's clear that the concentration of dichromate is too high for my negative. That's why I think that next time I should try a weaker sensitizer, while keeping the exposure time unchanged. Weaker sensitizer means lower sensitivity, so I guess I'd better not shorten the exposure yet. Does this sound like a good strategy?
     
  24. paul_c5x4

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    Using a negative that printed fine on grade 2 paper, after doing some test strips, arrived at a three minute exposure on a tissue that had been soaked in 2% potassium dichromate for three minutes. Anther neg I've been working with, I dropped the dichromate down to a 1% solution, soaked for five minutes and exposed for six minutes - Contrast isn't quite where I want it yet, so I'm going to try a 0.75% dichromate next.

    A 3% dichromate solution sounds way to high in my limited experience, so I'd suggest 1% or less (maybe even 0.5%) and do a test strip.
     
  25. Vaughn

    Vaughn Subscriber

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    Vald, what light source are you using and for how long?

    It seems to me that if the tissue gets too hot during the exposure, I have problems getting the unexposed gelatin to melt. I have not tested this further, but too much heat does seem to cause some problems the few times I have come across it -- exposing in the sun, for example.
     
  26. Vlad Soare

    Vlad Soare Member

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    It's a fluorescent facial tanning lamp. It doesn't seem to give too much heat. Although the body of the lamp itself does indeed heat up, I never noticed the contact printing frame or anything else in the darkroom to be warm to the touch after the exposure. The exposure was twenty minutes, which works well with vandyke prints (though, now that I think of it, vandyke negatives are much more dense, so maybe the time for vandyke wasn't exactly the most appropriate starting point).
     
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