Gumprint: do I have what it takes?

Discussion in 'Alternative Processes' started by argus, Feb 7, 2006.

  1. argus

    argus Member

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    Hi all,

    I'm in love with the appearance of gum prints and decided to start with the process from 13x18cm (app. 5x7") negatives.

    I have following stuff waiting to be used:
    - gum arabic (bulk);
    - potassium dichromate (bulk);
    - various color samples to play with;
    + quality watercolor paper, brushes, roller, contactprinting frame (in the make).

    I've been reading a lot on the process lately and I modestly can say that I understand the workflow.
    Some sources say that you should coat the paper a first time with a gelatine layer, others don't mention it. I'm a bit confused on that part.
    My question: is it (really) necessary to precoat the paper?
    Any further tips are welcome.

    All I have to do now, is wait for the sun to gain strenght!

    tnx,
    G
     
  2. Donald Qualls

    Donald Qualls Member

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    Depends on the paper.

    The idea of subbing with gelatin, relative to gum, is to ensure that gum and sensitizer don't penetrate into the paper fiber where the gum can't wash away and the sensitzer stain may become permanent. Some papers have enough sizing that this isn't a problem, others require a sort of "seal coat". The only way I know to tell is either to ask someone with experience using the specific paper you have on hand, or try some.
     
  3. argus

    argus Member

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    Thanks Donald.

    I guess I'll give the paper a try.

    I've got 2 brands: Arches and Fabriano.

    Greetings,
    Geert
     
  4. Lukas Werth

    Lukas Werth Member

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    Do you want to try single or multiple gum? You will most likely need - on any paper - a prior sizing with 3% gelatine (including hardening) for multiple gum.

    And, what contrast range do your negatives have?
     
  5. argus

    argus Member

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    first things first: single gum for the learning process (handling, exposing...)

    Lukas,
    Is there any preference for the contrast range?

    G
     
  6. Poptart

    Poptart Member

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    Mostly has to do with adhesion; a wc paper with a lot of tooth should absorb enough color that it won't require sizing. If you're printing multiple colors, though, you need to shrink the paper in hot water for about 10 minutes, then dry it, before proceeding
     
  7. Lukas Werth

    Lukas Werth Member

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    Negatives for gum, particularly single gum, should have a limited contrast range of about 0.7 (such as you would choose to enlarge on harder paper), or otherwise you are likely to get empty highlights or shadows.

    Single gum is quite different from multiple gum, in aesthetics as well as in the technique. Don't think it is easier. I once had the opportunity to inspect original prints by Robert Demachy in Paris (single gum prints) which had an absoulutely intriguing tonal range and quality, and I must confess I would not be able to make them. Single gum prints in my experience have the tendency to either lack density in the shadows / maximum density, or to become harsh, or both. But if you get everything right...
    You most probably will not want additional sizing with single gum, at least not if you are looking for fine highlight tones, but it will be essential - or near essential - with multiple gum to prevent staining. You can print down larger contrast ranges by first printing the highlights and then the shadows, and it is much easier to get the shadows right. You can use multiple colours. It is, of course, time-consuming, and you need a technique of re-registration. This problem increases with the size of your prints. Contrast can also be separately influenced in every layer you coat.
     
  8. argus

    argus Member

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    Thanks for the explanation, Lukas.

    Luckily, I do have some 13x18 negatives with limited contrast to play with first.


    G
     
  9. donbga

    donbga Member

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    Having read through this thread I've noticed no one has mentioned specific hardners for gelatin sizing. I would recommend glutaralhyde. I've had great results with it. Working on unsized paper will almost certainly cause staining. The only gum printer that I know that doesn't size and doesn't get staining is Sam Wang.

    Single coat gums are all but impossible to produce with any sense of depth and pleasing tonality. Be prepared to do multiple coats as Lukas has suggested.

    Pre-shrinking is also an absolute must for proper registration for multiple coat gum prints. You can register by eye by placing the coated paper on a light box and then laying the negative on the paper. Using a sheet of glass on top of the negative will allow you to press the negative/paper sandwhich flat to get good registration as a dried gum print will be quite curly. Once the negative is registered, tape it down carefully with low adhesion transparent tape.

    Oh yeah, printing by sun will drive you crazy trying to get consistent results, a better plan is to buy or make a UV exposure unit.

    Don Bryant
     
  10. cjarvis

    cjarvis Member

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    In my experience you don't need any sizing for gum. Just pre-shrink the paper.