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  1. #1

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    sizing for gum: gelatin over acryl?

    i print using unhardened gelatin. i can't get formaldehyd and the last time i checked glyoxal was very expensive. and secondly, i'm actually glad not to have yet another poisonous ingredient around. im uncomfortable enough with the dichromate.
    so, i do have some problems with stain. not the usualy yellow dichromate stain (i got that one too sometimes, but it doesn't bother me as much), but little specks of pigment. it seems to have something to do with the surface of the paper, because usually they occur in patterns like that, but not all over the print, only in small areas. they're completely stuck on the paper and can't be removed at all, not with brushes or other things.

    so, since a size with acrylic medium always gives me bad results (see pic. 1), why not use a gelatine coat above it? you get the barrier between paper and emulsion (the acrylic med.) and the surface texture of the gelatine.
    are there any objections to using both sizes? i will try some kind of gesso next. i read on the alt.process list that it should have "more tooth", so maybe the gelatine will adhere better

    pic 1 - acrylic medium only


    pic 2 - acrylic and gelatin

  2. #2

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    A few thoughts, in no particular order:

    I don't remember glyoxal being all that expensive, but you don't need to use much (I use 3 ml in 200 ml water/gelatin) so a bottle goes a long, long ways. But that's just an aside, not an answer to your question.

    It seems like your question has two parts: (1) is it okay to use unhardened gelatin as a size? The answer is yes, it's perfectly fine, and I sized with unhardened gelatin at one point in my early gum printing career. The only concern with unhardened gelatin would be that in areas of pure white, like the snow in your picture, the gelatin won't get hardened and might possibly serve to tempt bugs in the future. But rinsing the finished gum print with hot water will wash off the unhardened gelatin, if you're concerned about that, and won't affect the hardened gum. In any exposed areas, the underlying gelatin size will get hardened by the dichromate along with the gum, so there's no worry there.For visual demonstrations of these principles, see my page on issues in using unhardened gum for a size:

    http://www.pacifier.com/~kthayer/html/Gelhard.html

    (2) The second question seems to be, is it okay to combine the acrylic with the gelatin? I think the only concern here, where you're layering the gelatin on top of the acrylic, might be adhesion of the gelatin over time, but I doubt anyone's looked at that, since this is an unusual treatment. I'd guess that if it will adhere when coating, then chances are it's there for good, but I'm not a conservator.

    As I say in my page on sizing, my favorite size is a mixture of gelatin and gesso, but I haven't used it much for exhibition prints because I don't know anything about the archival properties of such a mixture. But at the same time, I don't know of any reason to suspect that it wouldn't be permanent, so it's perhaps overcautiousness. If you're interested in how I do that, instructions can be found on that page:

    http://www.pacifier.com/~kthayer/html/size.html

    Katharine

  3. #3

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    thanks, i'm currently spending a lot of time reading the alt.process mailing list archive. i saw the thread on bugs. i guess i'll switch to hardened gelatin if i ever sell a print...
    i remember seeing glyoxal in one of the us-mailorders for a reasonable price, but not here. none of the germany photo mailorders carries it and when (special) ordering in the local drugstore it will cost me 40 euro for 100ml, iirc. ... it's europe, i'm also paying 25euro for 50gr of ammonium dirchomate.

    i'll give the gesso and the mixture of gesso and gelatine a try next. until then i'll stick to gelatin over acryl and see how the works in the long term.
    another thing i'm wondering is, do most gum printer put a layer of size between each layer of gum? because that's what i am doing: gelatin - gum - develop - dry - gelatin -gum - develop.... i thought that's the usual, but i'm not so sure about that anymore.

  4. #4

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    Part of th fun/frustration of gum is the variables. Paper and sizing are big important variables. Don't count on just "switch to hardened gelatin if i ever sell a print". That switch may seriously mess with your prints!

    The amount of hardener (formalin, glyoxal, glut) used is very small, so with careful use it is reasonable safe. I've (with my papers and working methods) had very bad experience with unhardened gelatin. Too much pigment stain and grain. I find (with my papers and working methods) I get better results without a size (compared to unhardened size). If you are determined (for cost or health) to avoid hardening, try a well sized paper (Fabriano Artictico Extra White) with only a room temperature pre-shrink treatment. It will give you a few coats before staining.

    You can order small quantities of glyoxal from Bostick and Sullivan, You can order small quantities of glut from Photographers Formulary. I don't know what can be shipped to Germany (or at what cost).

    I (typically) only re-apply size after 4 color layers.

    Hope that helps,
    Tom

  5. #5

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    Quote Originally Posted by phritz phantom View Post
    thanks, i'm currently spending a lot of time reading the alt.process mailing list archive. i saw the thread on bugs. i guess i'll switch to hardened gelatin if i ever sell a print...
    Gracious, that's quite an undertaking (reading the alt-photo archives). There's a lot of good information on that list, and there were some great discussions in the old days (not so much for the last couple of years) but there's also a great lot of misinformation mixed in with the good stuff (moreso recently than in days gone by; we as a group of gum printers had made good progress toward debunking many of the old myths that needed debunking, when new people came along and started creating new myths that will have to be debunked by the next generation of gum printers) so take it all with a dose of salt and do your own testing before you decide which is which. Careful observation, rather than accepting the pronouncements of experts (myself included of course) is key to success in gum printing. I'd suggest less reading and more printing may get you there faster, but whatever works for you.

    As to switching to hardened gelatin for archivality, I'm not sure why you think that would be necessary. if you looked at the page I linked, it should be clear that rinsing the print with hot water after it's dry will remove any unhardened gelatin in unexposed areas without disturbing the hardened gum and gelatin in exposed areas, and even that shouldn't be necessary unless there are expanses of unexposed areas within the print or borders. So I wouldn't be concerned about bugs, if I were you, as long as you take that one precaution. Many people who size with unhardened gelatin don't even worry about that; I just recommend it to be absolutely sure, and as I said, only necessary if the print has substantial areas that are pure white (entirely unexposed).

    Re the question about sizing between layers: that isn't usually necessary, and most people don't, although there are probably exceptions as there are exceptions to every "rule" in gum printing. But in my observation, most people find one sizing supports as many layers as they want to do. If people are doing really a lot of layers (more than six, say) then they may find that they need to size again before going on to the ninth or tenth layer But that's sort of beyond the usual gum experience.
    Katharine
    Last edited by Katharine Thayer; 08-20-2008 at 10:41 AM. Click to view previous post history. Reason: fix unclarity



 

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