Carbon highlights "eaten out"

Discussion in 'Alternative Processes' started by gattu marrudu, Feb 7, 2013.

  1. gattu marrudu

    gattu marrudu Member

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    Hi,
    I'm still on my Carbon learning curve and I'm starting to get some predictable results.
    One thing I can't get over, though, is that all my highlights (zone VIII and IX approx.) look like "eaten out", i.e. beyond zone VIII the gelatin/pigmant is completely gone.

    Highlights look like large white holes. The other gradations are perfectly smooth.

    I'm using the pre-fabricated tissue from B&S, spirit sensitized with 2%-4% potassium dichromate (12ml for an 8x11 sheet). As a support, I'm using Fabriano Artistico paper with an 8% gelatin sizing (20ml with 4 drops of formalin for a 11x14" sheet, hotdog-rolled). Never had major detachment issues.
    I develop my print by turning it face down after de-mating and let it float without moving in 95-105F (35-40C) for 15-20 minutes.

    What could I be doing wrong?

    Thanks
    gm
     
  2. Vaughn

    Vaughn Subscriber

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    My guess is that between the low amount of dichromate in the tissue and the density of your highlights, the tissue just is not receiving enough exposure in your highlights to harden any of the gelatin -- thus no image. I would just try a 8% solution of sensitizer and see what happens -- it will lower the over-all contrast and hopefully keep your highlights without flattening the other values.

    It is difficult to compare results with different tissues, etc. My home-made tissue has a much lower contrast 'grade' than the B&S tissue, as I use a lot less pigment. My negatives are also have a very high DR...never actually measured it, but it they are probably well over 2.2. For an 8x10 (9x11 tissue) I am spirit sensitizing with 5ml of 8% Ammonium dichromate (diluted with 15ml of acetone -- so that equates to 20 ml of a 2% solution).

    Good luck!

    Vaughn
     
  3. gattu marrudu

    gattu marrudu Member

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    Vaughn, thanks for your reply.
    I tried concentrations and exposures at several different ranges, from 2% to 6% (I use twice as much as solution as you, so my 2% is your 4% in terms of dichromate per square inch).
    Exposing longer would give me a smooth tonal range in the highlights, but the image is too dark. When my highlights approach the desired value (zone VIII), there is a sudden drop in density. If I were to draw a curve, you would see a steep drop in the lower densities instead of the typical carbon toe.

    Where I would expect to see zone VIII and IX grays I see paper white. So I doubt it's the highlights being underexposed.

    It looks like the gelatin gets particularly fragile when it's thinner and falls off, even if I use no agitation in development. I'll post a scan of my test strip when I have access to it.

    I also wondered if I was using too little solution and missing spots during my brushing. I prefer 12ml for a 8x10 so I get a more uniform coating, but if you say you use half of the amount of liquid, maybe that is not the problem.

    Thanks
    gm
     
  4. Vaughn

    Vaughn Subscriber

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    Actually, I use 20ml of liquid for an 8x10. I just base my sensitizing on the strength and amount of stock solution (5ml of 8%) that I then dilute 1:3 with acetone (5ml + 15ml). If I was using alcohol instead of acetone, I might use it 1:2 (for a total amount of 15ml). Acetone evaporates so fast that I like using a little more than I did when using alcohol. But in the end, I am still delivering 0.4 grams of dichromate per sq inch (a nice mix of units there. LOL!)

    I have seen such highlights as yours in workshops I have given. There has been two causes that we were able to correct. 1) digital files that clipped the highlights. or 2) too low of a concentration of sensitizer (not enough dichromate) used to compensate for negatives that had too low of a contrast range.

    In your case, it just sounds like your negatives have too much contrast for the B&S tissue, but without seeing the negatives, I am not 100% sure of this.
     
  5. gattu marrudu

    gattu marrudu Member

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    That makes sense. So I'm indeed using much less overall liquid, and actually I can see some irregularities on the surface.

    From my previous experience with other dichromate processes, where I brush sensitized clear gelatin, if I hesitated just a fraction of second while brushing, the first brush strokes would show up clearly as more intense orange patches. You can't notice this on the pigmented carbon tissue, but dry gelatin is very thirsty.

    I might try pre-brushing some distilled water (with some acetone, but not too much or it will dry out too fast) in order to get the surface slick and have the dichromate spread more evenly.

    I can also try to size my support in two 4% gelatin coats instead of one 8% coat. The thicker gelatin might create a rough surface that compromises the adhesion of the support.

    I'm not quite following you on the dichromate amounts. 5ml of 8% concentrate makes 0.4 g of dichromate for your 8x10" sheet, which makes 0.005 g/sq. in - right? I'm using 12ml of 2% solution on a 8x11", which makes 0.0027 g/sq. in, so it has more contrast.

    I don't have a densitometer, but I can say my negative is quite thick but not too contrasty.

    Thanks for your advice, I'll let you know how it goes.
     
  6. banana_legs

    banana_legs Member

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    Hi,

    I have had the same problem of loss of highlights and it can occur if the sizing on the paper is not hardened quite enough; I think of the problem as a 'micro frilling' issue where the very thin highlight gelatine does not quite stick well enough to the support. The sizing is hard enough to stop much of the frilling issues, but not quite strong enough to hold onto the highlights. Try painting on a 5% solution of formalin onto a sheet to harden it some more and see if the highlights change.

    I also have had the problem when the mating bath was too alkaline and the gelatine sizing on the paper gets a slightly 'slippy' feeling in the mating bath. A dash of citric acid solution (e.g. stop bath) can help in this case and I now slightly acidify the mating water routinely now as it always seems to have a positive benefit with image adhesion.

    Best regards,

    Evan
     
  7. Vaughn

    Vaughn Subscriber

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    Sorry, I wrote a response right away, but must have forgotten to click on "Submit reply"!

    And sorry for the math error. I meant that a tissue for an 8x10 negative gets a total of .4 grams of Ammonium dichromate. The actual tissue size is 9x11, close enough to call it 100 sq inches, so I use 0.004 grams per sq inch. The amount you use per sq inch is what I standardize on for my workshops, and I consider 0.0005 per sq inch to be about the lower limit.

    But the B&S tissue has a much higher inherent contrast than my tissue I use and that I make for my workshops.

    I use fixed out photo paper for my own work and for the workshops. So I have not witnessed the mirco-frilling...but will keep an eye out for it in the future.

    Good luck in refining your process!

    Vaughn
     
  8. gattu marrudu

    gattu marrudu Member

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    I have tried with acidifying the mating bath, but the problem still persists.
    As for the substrate hardness, that's interesting - I just gave my paper a further formaldehyde coating. In this case, is it advisable to rinse the paper after it has hardened, so the formaldehyde doesn't seep into the carbon tissue during mating and harden it?

    Attached is a detail of a print where the highlights appear as a white pool - yes, the negative is very grainy, but I would still expect a smoother gradation from light grey to paper white.

    Thanks
    gm
     

    Attached Files:

  9. banana_legs

    banana_legs Member

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    Hi,

    Yes I often give the paper an extra wash a few days after the formaldehyde step just to be safe. I have used paper by accident that had been coated with formaldehyde 24 hours earlier without washing it and it was ok; the mating bath will help was out residual formaldehyde but I did pull the tissue after 20 minutes just in case.

    Best regards,

    Evan
     
  10. CMB

    CMB Member

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    It is painful to read of your quest for highlight detail in con-tone carbon printing. While many will come forward with advice the sad truth is that carbon prints have a well-documented problem with the loss of highlights (see the 11-17-11 APUG Post: Highlight Loss in Carbon Printing) This can easily be seen when printing a step wedge, but most carbon enthusiasts print "pictures" and are satisfied with the results of their efforts.

    Charles
     
  11. gattu marrudu

    gattu marrudu Member

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    I will include your link here for convenience: http://www.apug.org/forums/viewpost.php?p=1259943
    Having that important information in mind, in my case I can change the way I want my prints to look. I moved to carbon from palladium with the specific goal of getting better shadow details, which Pd was giving me a hard time with. The prints are in low key and I can tone down the highlights without having the picture sell its soul to the devil.

    Thanks!
     
  12. Vaughn

    Vaughn Subscriber

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    I do not seem to have many problems with eaten out highlight when printing carbons from continous-tone negatives. Perhaps I have not noticed it. The one or two times I have noticed it it has been due to, or I have attributed it to, over-developed negatives.

    The below might be of some limited help. I rephotographed a 8x10 carbon print with a digital camera and the quality of the reproduction is suspect.

    The highlight section that is enlarged is out in the sun (on white granite), compared to the heavy shade of the foreground. There is detail in the highlights.
     

    Attached Files:

  13. banana_legs

    banana_legs Member

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    Hi Charles,

    Yes I completely agree with you and the post you referred to that good highlight detail is always going to be an issue with carbon and con-tone negs. I have found however that it is possible to make the problem even worse if the receiving substrate is not well sized. The problem can also be worse if very high sugar concentrations are used in the glop; the gelatine layer is almost 'softer' then and more prone to washing away in development. I have also had more issues with thin, highly pigmented tissue, rather than thick tissues with low pigment concentrations, I have assumed being due to less gelatine being needed for the highly-pigmented case and so the highlight layer is very thin.


    Best regards,

    Evan
     
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  15. gattu marrudu

    gattu marrudu Member

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    I was just thinking about that. So if instead of using B&S's tissue (which is great to start with, but thin and very concentrated in pigment AFAIK) I made my own glop, thicker and with less pigment, would that help?

    The fact is that my highlights are REALLY bad sometimes, so I cannot really blame it completely on the tissue. I can't imagine B&S selling a tissue which yields such bad results for reasonably processed prints.

    But, trying to rule out all other factors, I tried acidic mating bath, double hardened substrate gelatin, even fixed out silver photo paper. The highlights are still being washed off. So I will try brewing my own glop next.
     
  16. Vaughn

    Vaughn Subscriber

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    Since I make my own tissue and I use the minimum amount of pigment, my highlights will actually be made of a thicker layer of gelatin than using a tissue with a much higher pigment amount. This is what could be protecting my highlights from being 'eaten out'.

    I use 4 grams of lampblack watercolor paint (from tubes) to 750 ml water, 90 grams gelatin (food grade) and 60 grams sugar. Different brands of watercolor will contain different amounts of lampblack...so one needs to standardize on one brand if one goes that route.
     
  17. banana_legs

    banana_legs Member

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    Hi Gattu,

    The temperature of the developing water can also have an effect too (quite a subtle effect, but sometimes noticeable); I recently did a run of 6 prints in quick succession and used the same developing water for them all. The water was in a tray sat on top of a water heater plate, which does not have good temperature control. Over the course of the prints, the 'blown highlight' regions around some lamps that were in the image got larger and larger, yet the shadow areas and rest of the image looked exactly the same. It took me a while to realise that it was the temperature of the developing bath that had been slowly increasing between the prints, making the print contrast just slightly higher for each successive print.

    The first print was developed at 41 degrees and looked fine, the 5th at 47 degrees and much detail in the lamp area that was present on the first print was lost by the 5th print (I was floating the paper face-down to develop for 30 minutes). For the final print, I turned off the heater until the water had cooled to 40 degrees, then turned the heater back on during the development, giving a similar temperature profile to the first print. The result was that the first and the last print looked near identical, indicating that the exposure and sensitisation was consistent between prints too and only the temperature of development had varied for the others.

    The negative was unusual for me in that it was a picture taken in a dark room with a few lamps that essentially were blown out in the print and did not have a good tonal range. I printed to capture the detail in the room and so knew the lamps would print white. It was the size of the 'halo' around the lamps which grew as the temperature of the water increased. I assume that the hotter water softened the gelatine more. On inspecting the print for 'correct development', I stopped the development when the bulk of the room looked right, rather than the highlights. Thus it was not as if the prints were overdeveloped as the rest of the image looked fine, rather the contrast of the image had changed.

    Best regards,

    Evan
     
  18. mark

    mark Member

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    Pardon my ignorance but what does con-tone mean?
     
  19. Vaughn

    Vaughn Subscriber

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    Continous-tone negatives (such as the ones we get from our cameras), as opposes to one made of dots for screen printing.
     
  20. Andrew O'Neill

    Andrew O'Neill Subscriber

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    When I went to a higher pigmented tissue (16g per litre 9% glop), I found it challenging to preserve large, smooth areas of highlights, especially with digital negatives. Going back to 6g was much better. Are you using in-camera or digital negatives?
     
  21. gattu marrudu

    gattu marrudu Member

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    Neither one - I'm using 35mm TMZ mechanically enlarged to 7x10", which gives me quite some grain.

    @Evan: I haven't felt the need to standardize development yet. Until I have to pull an edition, I can just lift the print and see what it looks like. My temperature goes over 40C sometimes, which might be destroying the thinner layers of gelatin.

    Also, I noticed visible differences between supports treated differently (more or less sizing, one or two coats, more or less formalin). Hot-dog rolling leaves a relatively rough texture, which I am concerned might create micro-bubbles or weaker points during mating. So even if up to 10% concentration is suggested for gelatin, I prefer two coatings of 4% and roll until the gelatin starts to set and yields a finer texture.
     
  22. Photo Engineer

    Photo Engineer Subscriber

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    Talk to Bob Carnie about this.

    PE
     
  23. Andrew O'Neill

    Andrew O'Neill Subscriber

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    Try developing at a lower temperature. I stick to 39C.
     
  24. Andrew O'Neill

    Andrew O'Neill Subscriber

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    Hi Vaughn,
    With this amount of acetone, how long does it take your tissue to dry (taking RH, etc into consideration)? I've always used 1:1, but if it speeds up drying I may give it a go. Thank you.
     
  25. Andrew O'Neill

    Andrew O'Neill Subscriber

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    .

    Have you tried pouring a small amount on the support and coating with a copper pipe? You end up with a nice, smooth surface. Smooth surfaces seem to work better.
    I size my papers with acrylic medium (hot dog roller). They have a slightly rough surface when dry, but when I zap it in a dry mount pres,. I end up with a very nice, smooth surface.
     
  26. Vaughn

    Vaughn Subscriber

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    One hour in Sacramento, two hours in Eureka. I do not use any material between the negative and the tissue, so I wait a little longer than may be needed to insure that I do not damage the negative. The additional volume also helps (I think -- not tested) to get the dichromate evenly spread around and into the tissue (since I am using a thick tissue -- 1.2 ml of glop per square inch).

    Vaughn