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  1. #191
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    Charles;

    Thanks for the clarification.

    I have about 50 feet of full width Ultrastable here as well as several pads of Yupo. See above for others using Yupo. It seems to be ok. As for coating on Estar / Melenex type films, Kodak coated regularly on ~4 mil, 5 mil and 7 mil Estar using corona treatment.

    PE

  2. #192

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    Tod Gangler on pigments

    I've had a chance to organize the last of my notes from my conversation with Tod Gangler last weekend, and supplemented with some findings of my own.

    We talked about pigments a bit, and he introduced me to a concept known as "pigment shock". This was a new term to me, but apparently well known in the paints and industrial coatings universe. In doing a little digging on the 'net later, I found out that when introducing a pigment in suspension into a vehicle (in this case, our vehicle is melted gelatin), various interactions between the temperature of the 2 components, and physical interactions of the solvents/binders/etc. in each case can cause the pigment particles to flocculate, causing an increase in particle size (which also means a reduction in tinting strength) and a tendency to stain, due to larger particles being more likely to fall out of suspension.

    For this reason, Tod recommends pigments in aqueous suspension (as opposed to watercolor tubes), and further recommends that the aqueous suspension be further diluted with water, (I assume to both reduce viscosity and concentration), and brought up to the temperature of the gelatin before incorporating.

    With further regard to pigments, he noted that one of the pigment suppliers (manufacturers) he has used in the past has gone out of business, and he is not sure he could order in the same (relatively) small quantities from 2 others. For newcomers interested in color carbon, he recommended the Kremer color concentrates. The pigments which he uses were no surprise: pthalo blue green shade, quinacridone magenta, and one of a few different yellows, bismuth vanadate, permanent (benzimida) yellow, and isoindolinone yellow.

    My note: as near as I can tell, these would be PB15:3, PR122, PY184, PY154 (possibly PY151) and PY109. I'm guessing that the isoindolinone is PY109, the green shade, as opposed to PY110, the red shade. Handprint.com does not address PY109, and it's not one I've seen in previous discussions about tricolor pigments.



    I hope this info helps somebody out there...

    --Greg

  3. #193

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    Quote Originally Posted by gmikol View Post
    For this reason, Tod recommends pigments in aqueous suspension (as opposed to watercolor tubes), and further recommends that the aqueous suspension be further diluted with water, (I assume to both reduce viscosity and concentration), and brought up to the temperature of the gelatin before incorporating.
    --Greg
    Thanks Greg! Tod's information is very precise as allways, and is in line with my findings. I'm also using the Kremer concentrates (see this post for direct links). For monochrome work I sometimes work with bulk archival inkjet inks. Especially one carbon black, Epson Ultrachrome replacement ink, sold by MIS as Eboni black. It actually comes from Image Specialists (WJ1082). I never tried full CMYK carbon with inkjet inks but that should work. I allways felt using inkjet inks was a bit cheating... At least colours are nicely balanced out of the bottle.

    Inkjet inks are very finely divided and kept in suspension by some extra's, mainly glycol. I never saw any side effects from these extra chemicals. The Kremer pigments concentrates contain also dispersion agents and differ quit a bit how the keep in suspension in their bottle. The bismuth vanadate yellow is the most difficult to keep in suspension. The other 3 colors not. Finding the right colorbalance is also somewhat difficult! I am using these several years for tri-color gum, so I knew them allready. As a rule of thumb one needs equal parts (in weight) of the K (1 part) and C (1 part), a little less M (0.8 part), and a lot more of the bismuth Y (1.6 part).

    Regarding the colorconcentrates: I allways dilute the pigment with water and bring this to temperature before mixing. The mixed glop I keep for at least one hour on a temperature controlled magnetic stirrer with the temperature sensor in the mix. The also warm DAS (3% in water premixed) goes in at this last stage. be careful to use safelight from that moment. I count for this extra water added when making the gelatin mix.

    The Kremer isoindolinone yellow (PY109) can be found here and the Permanent Yellow (PY154) here.

    -k
    Last edited by keesbran; 09-26-2012 at 03:42 AM. Click to view previous post history. Reason: extra links

  4. #194
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    Awesome discussion; you guys are seriously getting down to brass tacks.

    Just a quick update from me: haven't heard from Secant for a couple weeks, and I've sent a note to Tod to see if he received the sample. If not, I need to get on the phone to Secant. Hopefully it's just a lapse in communication, nothing more.

    So far, 11 kilograms is spoken for, and there are a handful of people on the list who haven't provided me with quantities; so that number is likely to rise a fair bit.

    OVER and OUT
    If you are the big tree, we are the small axe

  5. #195

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    Diazo-Carbro

    Does anyone know if Diazidostilbene would work in the Carbro process? I'm interested in experimenting with carbon/bro and related processes in general but carbro in particular draws my interest. Relatedly does anyone have a description of the chemical process that underlies carbon/bro. I've been looking around for one but most I've seen are more a description of how to produce a print then the underlying chemistry.

  6. #196

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    Chemically speaking, carbro and carbon are very different. Carbon transfer is an ultraviolet light sensitive process. The UV light reacts with a traditional sensitizer (potassium or ammonium dichromate), or with a "modern" sensitizer like we're discussing here, causes the gelatin to harden in proportion to how much light it received in order to trap pigment in the gelatin. You wash off the remainder in hot water, and are left with an image.

    Carbro is a purely chemical process. It uses a very different sensitizer, which, when the sensitized carbon tissue is brought into contact with a conventional silver gelatin print, reacts with the silver and causes the gelatin in the carbon tissue to harden. The more silver (darker areas on the print), the more hardening of the carbon tissue.

    There it is in one paragraph each.

    William Crawford, "The Keepers of Light"
    Richard Farber, "Historic Photographic Processes"
    Sandy King, "The Book of Carbon and Carbro"

    These 3 all have decent descriptions of the similarities and differences between the 2 processes. The first 2 are out of print, AFAIK, and the 3rd is self-published. Some google searching might yield some hits, too.

    To others on this thread...I don't own any of Nadeau's books. Does he address carbro at all?

    Hope that helps...

    --Greg

  7. #197

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    Quote Originally Posted by gmikol View Post
    Chemically speaking, carbro and carbon are very different. Carbon transfer is an ultraviolet light sensitive process. The UV light reacts with a traditional sensitizer (potassium or ammonium dichromate), or with a "modern" sensitizer like we're discussing here, causes the gelatin to harden in proportion to how much light it received in order to trap pigment in the gelatin. You wash off the remainder in hot water, and are left with an image.

    Carbro is a purely chemical process. It uses a very different sensitizer, which, when the sensitized carbon tissue is brought into contact with a conventional silver gelatin print, reacts with the silver and causes the gelatin in the carbon tissue to harden. The more silver (darker areas on the print), the more hardening of the carbon tissue.
    Ah! this explains my confusion. While I was aware of much of what you wrote I for some reason had it in my mind that carbro used the same dichromate sensitizers + non-supercoated bromide paper + some special bleach to achieve the chemical hardening. I must have conflated carbro and ciba for some reason.

    Edit: Speaking of pigments earlier, has anyone studied whether color carbons benefit from using more then the standard CMYK colors? I'm thinking of things like Hexachrome, CcMmYK, or PMS that use additional colors to improve color reproduction among other things. In theory you could also add interesting special effects. Take a normal light and UV photograph of a flower and use normal and UV fluorescing pigmented tissues so that under normal light it displays as the normal light photograph and under UV as the UV.
    Last edited by Orioes; 09-28-2012 at 11:37 PM. Click to view previous post history.

  8. #198
    CMB
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    Quote Originally Posted by Orioes View Post
    Does anyone know if Diazidostilbene would work in the Carbro process?
    Good question. Dichromate is one of the chemical components of the carbro bleach. Whether or not DAS can be used in those formulations in place of dichromate, AFIK, has not been tried. My guess is that because gelatin does not spontaneously harden (cross-link) in the presence of DAS as it does with Dichromate, the answer is, probably not. A chemist could tell you why.

    Charles
    Last edited by CMB; 09-28-2012 at 11:44 PM. Click to view previous post history. Reason: Format

  9. #199

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    The Chinese Envoy was here!

    Yesterday I received some DAS directly from Shanghai. Tested it today.
    It's somewhat more light sensitive than my previous locally bought provision. And a very fresh batch.

    -kees


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  10. #200
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    I can make separation bromide prints on fibre or rc black and white paper> if anyone here wants to try to work out a Carbro workflow I will collaborate and supply the separated silver prints.
    This is not a direction I am currently exploring but since I make silver gelatin positive prints as a matter of course, making negative bromides are very easy for me to do.
    I have a ton of out dated rc paper black white which may work just fine.

    If anyone is interested and wanting to work in collaboration over the winter on tri colour carbro send me a email bob@elevatordigital.ca , I am set up to be able to work with more than one worker if there is interest.



    Quote Originally Posted by gmikol View Post
    Chemically speaking, carbro and carbon are very different. Carbon transfer is an ultraviolet light sensitive process. The UV light reacts with a traditional sensitizer (potassium or ammonium dichromate), or with a "modern" sensitizer like we're discussing here, causes the gelatin to harden in proportion to how much light it received in order to trap pigment in the gelatin. You wash off the remainder in hot water, and are left with an image.

    Carbro is a purely chemical process. It uses a very different sensitizer, which, when the sensitized carbon tissue is brought into contact with a conventional silver gelatin print, reacts with the silver and causes the gelatin in the carbon tissue to harden. The more silver (darker areas on the print), the more hardening of the carbon tissue.

    There it is in one paragraph each.

    William Crawford, "The Keepers of Light"
    Richard Farber, "Historic Photographic Processes"
    Sandy King, "The Book of Carbon and Carbro"

    These 3 all have decent descriptions of the similarities and differences between the 2 processes. The first 2 are out of print, AFAIK, and the 3rd is self-published. Some google searching might yield some hits, too.

    To others on this thread...I don't own any of Nadeau's books. Does he address carbro at all?

    Hope that helps...

    --Greg



 

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