Multilayer gum printing - adhesion

Discussion in 'Alternative Processes' started by walter23, Feb 26, 2010.

  1. walter23

    walter23 Member

    Messages:
    1,189
    Joined:
    Sep 19, 2006
    Location:
    Victoria BC
    Shooter:
    4x5 Format
    I'm trying to figure out multi-layered gum printing, and the problem I'm having is that the second layer doesn't adhere. I may have not had enough dichromate in the sensitizer for my second layer (I mix very small amounts at a time (0.3 grams of potassium dichromate in 3-4ml water), and my scale has an error of +/-0.1 grams), but I wanted to see if there were other possible problems to consider.

    WHen I printed my second layer it started to develop okay, but then lifted away from all the exposed areas in solid clumps... so it hardened alright (or at least, to some extent), but broke up and didn't adhere.

    I do a sodium metabisulfite bath to clear dichromate stain; could that be impacting things if I didn't rinse enough? I'm not really sure what to consider here.

    I hope I don't have to size, but from what I understand sizing is about keeping pigment from adhering too much / staining, so I don't think that's what's going on here.
     
  2. Katharine Thayer

    Katharine Thayer Member

    Messages:
    252
    Joined:
    Jan 22, 2007
    Shooter:
    4x5 Format
    Walter, what are you printing on? In my experience/observation this is a problem that tends to arise when printing on hard surfaces (plastic, metal, or glass, for example) that have little tooth, or when a too-thick or too-heavy size is used on paper so that it fills up the tooth in the paper and doesn't leave enough for the gum to hang onto. It sounds from your comments like you're not sizing, so the second possibility shouldn't apply, and if you're using paper, the first shouldn't apply. Varying amounts of dichromate would affect the speed of the gum layer but if the gum is coming off in flakes rather than washing off as a liquid (meaning the layer isn't sufficiently exposed) then I don't think it's the dichromate that's at fault.

    Another question: how heavy is your pigment mix? If too heavily pigmented, it can chunk off like that, but if it's that heavily pigmented, you would have trouble brushing it on the paper as well.

    Metabisulfite should not be an issue here, at all.

    Hope any of that is useful,
    Katharine
     
  3. walter23

    walter23 Member

    Messages:
    1,189
    Joined:
    Sep 19, 2006
    Location:
    Victoria BC
    Shooter:
    4x5 Format
    I'm printing on Fabriano artistico hot pressed; no extra sizing added.

    Interesting you say that too much pigment can do that; I doubled up the pigment for the second layer thinking I could avoid colouring the highlights by having more pigment but a shorter exposure (was aiming for higher contrast). Also it brushed on with a bit of difficulty and I couldn't get a smooth coating, it seemed too wet / runny. (This was also a different watercolour that I noticed had both gum arabic & dextrin as the base, instead of just gum arabic, so maybe that's an additional problem).

    The first layer was a very small amount of pigment and a long exposure (to try to get the highlights filled in without adding much density to the dark areas; low contrast)... there was quite a bit of hardened gum on the paper after this (so you could really see the texture of it while it was wet; pretty serious relief). I had this "brilliant" idea to try to do something similar to split grade printing on multigrade silver paper (a low contrast exposure for the highlights followed by a high contrast exposure to fill in the shadows).

    Instead of doing these radical pigment concentration things maybe I should try just using a lighter pigment (like transparent yellow) for the highlight layer, then a dark pigment for the shadows?

    BTW, I have referred to your site quite a bit while learning this process; you've done some really nice stuff. Thanks for offering your suggestions.
     
    Last edited by a moderator: Feb 27, 2010
  4. Katharine Thayer

    Katharine Thayer Member

    Messages:
    252
    Joined:
    Jan 22, 2007
    Shooter:
    4x5 Format
    Hmm, I don't think we're talking about the same thing with the pigment; wet/runny doesn't describe the kind of heavily pigmented mix I'm talking about. I was talking about a mix that's so heavily pigmented it's like tar, and the difficulty I was referring to would be akin to trying to spread tar on paper with a brush. If a mix is wet and runny, I would say it's not heavily pigmented, by definition. Do you use extra water in your mix, or just the water in the dichromate solution? BTW, I'm not sure I see the reason for mixing such tiny amounts of dichromate; that seems like a lot of trouble to me.

    FYI: the same issue has been just recently been brought up on the alt-photo mailing list, someone having the same problem of third and later gum layers not adhering, same paper (Fabriano Artistico Extra-White) unsized.

    I don't use that paper, don't like it, but when I did try ten sheets of it just to see what all the hoo-ha was about, I found it a very absorbent paper, very easy to coat (which may be why so many people like it) which disqualifies it from the category of hard/slick/nonabsorbent materials that I was referring to in my earlier post, that can sometimes have difficulty hanging onto subsequent layers.

    Your thinking is good with the "split tone" idea; that's how generations of gum printers have printed both well-gradated highlights and dark shadows. Sorry it didn't work in this case. But there should be no problem with your method; I've done this routinely.

    I'm afraid I don't have any good answers, since the usual answers to this question don't seem to apply. Just grasping at straws, I'd say try a longer exposure for the second coat and see if that helps. Good luck,
    Katharine
     
  5. walter23

    walter23 Member

    Messages:
    1,189
    Joined:
    Sep 19, 2006
    Location:
    Victoria BC
    Shooter:
    4x5 Format
    Thanks Katharine; appreciate the help.

    For now I'll assume my first layer is okay and just try to sort out the second layer issue. I probably just made a bad batch of gum / sensitizer, it didn't seem to brush on right, and even a test print with just one layer of that batch didn't seem right to me (took a much longer exposure than normal).

    Should find a brown bottle and mix up a bigger batch of sensitizer to keep it consistent and make proportions easier to control. Does the dissolved dichromate solution last any reasonable length of time?
     
  6. DarkroomDan

    DarkroomDan Subscriber

    Messages:
    239
    Joined:
    Oct 4, 2003
    Location:
    Enumclaw, WA
    Shooter:
    Multi Format
    Katherine didn't toot her own horn. Click on the URL at the bottom of her reply and it will take you to her website where you will find a wealth of information on gum printing.

    Dan
     
  7. walter23

    walter23 Member

    Messages:
    1,189
    Joined:
    Sep 19, 2006
    Location:
    Victoria BC
    Shooter:
    4x5 Format
    Yeah, I have really enjoyed looking at her work and information... thanks for the reminder, lots of good information there.
     
  8. PVia

    PVia Member

    Messages:
    813
    Joined:
    Oct 3, 2006
    Location:
    Pasadena, CA
    Shooter:
    Multi Format
    AFAIK, the dichromate solution should last a long time esp in a brown bottle. I made my first bottle in May of 2009 and it's still perfect. Find a 100ml bottle and mix it up all at once. There's too much of a variable when mixing tiny amounts for one-time usage.
     
  9. sdivot

    sdivot Subscriber

    Messages:
    177
    Joined:
    Jan 14, 2005
    Location:
    Houston, Tex
    Shooter:
    Medium Format
    The easiest thing to do is just mix up a saturated dichromate solution. Keep adding water until no more will dissolve, and you have a saturated solution. You can keep this in a big amber bottle and keep adding water until the dichromate will eventually all dissolve. At that point, add more dichromate until it's saturated again. This way your mix will always be consistent. I think it will last a very long time.
    Just make sure you don't shake the bottle before measuring it out for your print, or else you will get dichromate crystals in your mix.
    Steve
    www.scdowellphoto.com
     
  10. walter23

    walter23 Member

    Messages:
    1,189
    Joined:
    Sep 19, 2006
    Location:
    Victoria BC
    Shooter:
    4x5 Format
    That's great advice and will definitely make things easier and more consistent.
     
  11. Colin Graham

    Colin Graham Member

    Messages:
    994
    Joined:
    Sep 5, 2004
    Shooter:
    Plastic Cameras
    Careful with saturated solutions if your darkroom temp fluctuates a lot, the saturation point can change a bit and effect the sensitivity.
     
  12. donbga

    donbga Member

    Messages:
    2,084
    Joined:
    Nov 7, 2003
    Shooter:
    Large Format Pan
    The saturation point does change but it has been my experience over many years that for a saturated solution of AD or PD there seems to be little effect from temperature changes as long as a large enough volume of dichromate lays on the bottom of the container.
     
  13. Colin Graham

    Colin Graham Member

    Messages:
    994
    Joined:
    Sep 5, 2004
    Shooter:
    Plastic Cameras
    My ambient temp varies on average 15C from morning to afternoon, which can represent a 30% change in saturation for ammonium dichromate according to one of the sources I could find. Maybe real world results aren't as dramatic as this table suggest, but I figure gum is capricious enough already without throwing in that variable on top. I do know I had difficulty getting consistent exposures when I did use saturated solutions.

    Anyway, to find the best concentration for my darkroom I just got some water as cold as my space gets, and kept track of how much would go into solution at that temp, then rounded down to the next whole number for good measure. Since I established this concentration my exposures have been constant.
     
  14. Sponsored Ad
  15. donbga

    donbga Member

    Messages:
    2,084
    Joined:
    Nov 7, 2003
    Shooter:
    Large Format Pan
    Which dichromate do you prefer? AD or PD?
     
  16. Colin Graham

    Colin Graham Member

    Messages:
    994
    Joined:
    Sep 5, 2004
    Shooter:
    Plastic Cameras
    I've had much better luck with AD, for both gum and carbon transfers. I know the opposite is true for many though!
     
  17. sdivot

    sdivot Subscriber

    Messages:
    177
    Joined:
    Jan 14, 2005
    Location:
    Houston, Tex
    Shooter:
    Medium Format
    FWIW, I use ammonium dichromate. Can't compare the two, since I've never used potassium dichromate.
    Good luck,
    Steve
    www.scdowellphoto.com
     
  18. Loris Medici

    Loris Medici Member

    Messages:
    653
    Joined:
    Sep 13, 2005
    Location:
    Istanbul, Tu
    Shooter:
    Multi Format
    I'm with Colin, I prefer to use *known/stable* solution strengths. I use ammonium dichromate at concentrations: 2.5%, 5%, 10% and 15% which are all stable (w/o crystallization) in reasonable room temperatures. (That is >= 18C/64F...) Not that it will definitely give you much more consistent results (since there are so many different critical variables in gum printing), but mind is easier that way... :wink:
     
  19. sdivot

    sdivot Subscriber

    Messages:
    177
    Joined:
    Jan 14, 2005
    Location:
    Houston, Tex
    Shooter:
    Medium Format
    I suppose if you work in a garage or a basement that is not climate controlled, then you should be more diligent about your concentrations. But my darkroom is in my house where the temp is pretty consistent throughout the year. I live in Houston, so humidity is a different story entirely. I'm not sure how, or if humidity affects your concentrations. Maybe someone else can interject.
    Steve
    www.scdowellphoto.com
     
  20. Loris Medici

    Loris Medici Member

    Messages:
    653
    Joined:
    Sep 13, 2005
    Location:
    Istanbul, Tu
    Shooter:
    Multi Format
    Even if there are substantial temperature fluctuations, I don't think it will affect the dichromate solutions strength too much, especially for a large volume like Don said. The effect would be negligible indeed. OTOH, why not nailing down a variable where you can? Gum is already pretty tough to control anyway...

    I also don't understand the practice of using saturated AD for making gum prints; even 15% is extreme in my experience. My usual dilution is 5% and it works like a charm with inkjet transparencies. I use 10% for single layer bleach developed prints where exposure times should be around 2-3x stronger than normal and 15% for non-oiled paper negatives . Strong dichromate concentrations tend to kill shadows too. (I use negatives with a relatively high density range BTW; negatives calibrated for trad. cyanotype.)
     
  21. Colin Graham

    Colin Graham Member

    Messages:
    994
    Joined:
    Sep 5, 2004
    Shooter:
    Plastic Cameras
    I standardized on 20% AD, but count drops like any other process. I also started pre-making dispersions of watercolor pigment and gum in known and repeatable concentrations. While that's hard to measure by dropper because of the viscosity, it does measure accurately in one of those graduated cough syrup spoons and gives much more consistent results than weighing- unless you have a very sensitive scale.
     
  22. donbga

    donbga Member

    Messages:
    2,084
    Joined:
    Nov 7, 2003
    Shooter:
    Large Format Pan
    Well FWIW, as mentioned before I use AD in a 'saturated' state. I meter the volume with a medical syringe which seems to be very accurate. I then add an equal volume of distilled water (BTW, I always use distilled water for AD solutions) so in the end I'm using about a 15% solution. I've heard several gum printers remark that much less dichromate can be used than many people typically use including myself.

    One very well known and experienced gum printer has told me about his method and he seems to use very small amounts of dichromate by comparison. But as in all things gum everyone uses what works for them.
     
  23. Loris Medici

    Loris Medici Member

    Messages:
    653
    Joined:
    Sep 13, 2005
    Location:
    Istanbul, Tu
    Shooter:
    Multi Format
    That's Sam I presume. (See: http://unblinkingeye.com/Articles/3CG/3cg.html) He is using an effective solution strength of 6% - I mean in terms of 1:1 gum/pigment+dichromate... I've started with 20% AD and reduced it to 5%, until I was getting good results with my procedures. Not a coincidence then...

    Regards,
    Loris.
     
  24. sdivot

    sdivot Subscriber

    Messages:
    177
    Joined:
    Jan 14, 2005
    Location:
    Houston, Tex
    Shooter:
    Medium Format
    I do the same thing Don does. When mixing my final solutions, I measure out the same amount of water as the Am Dichromate, thus diluting it. Sometimes I substitute more gum arabic for the water as well. So the final solution of Am Dichromate is not saturated. The jar of saturated solution, used as a stock, is just for convenience.
    Steve
    www.scdowellphoto.com
     
  25. Colin Graham

    Colin Graham Member

    Messages:
    994
    Joined:
    Sep 5, 2004
    Shooter:
    Plastic Cameras
    Many thanks for sharing your approaches, very informative. Good to know there is latitude in the process. I sometimes am too rigid to change things or explore more options once I get a little success with a certain approach.
     
  26. donbga

    donbga Member

    Messages:
    2,084
    Joined:
    Nov 7, 2003
    Shooter:
    Large Format Pan
    In case anyone is wondering for carbon printing - exact dilutions need to be used.