U of S | Mailing List Archive | alt-photo-process-l | Re: haunted GUM (related to judy's favourite pet peeve: the pigmentrat

Re: haunted GUM (related to judy's favourite pet peeve: the pigmentratio test)

well, thanks and howdy judy,
you're close, i live in austria and my mother tongue is of course german. i'm somewhat comfortable with english, but i'm never sure when and if i got my point across. so it always always feels like i'm writing too much. but since there are already some helpful answers, not everyone fell asleep while reading..

those are the pigments i always use: dry pigments made by Guardi. and 16% gum, mixed from chunks.the paper is cheap paper from boesner with a very fine surface, sized with gelatin and chrome alum hardened. i have about 15 or so colours around, some of which i have used a lot, other not yet at all. i used the iron oxide black for the test strip, because the phenomenon first happened with a highly pigmented iron oxide/ phthalo blue mix, and i wanted to find out what's happening here. it later occurred again with the burnt siena. i don't normally use the iron oxide black, because i never got good results and it stains heavily.

i don't really think that the desk lamp is the source of error here, but i just wanted to check to be sure. also it's a somewhat strange spot light bulb- i don't trust it. but the working distance (when registering ) is about half the time (max.) at appr. 10 times the distance. this test strip just happens to be the only one, in which i left a part covered with cardboard, so that it won't get any exposure at all.

i mentioned the pigment-ratio-test, because this could maybe be another part in disproving the test. it is the part that got zero exposure which stains (if this is stain) the most. in the area that got some exposure the gum dissolves better than in the area which got zero light.
this is also my main source of confusion here.

Judy Seigel schrieb:

On Tue, 6 Oct 2009, phritz phantom wrote:

(sorry for my total inability to write succinctly in english... my apologies)
can anyone put some sense in this? i'm completely lost. any tips, except trying even longer exposures?

If I read your address correctly, you're living in Germany, which could possibly mean your "mother tongue" is German? You write English like a native American however, so...enough with the apologies. My feeling at this moment is that if I had to go through what you're going through I wouldn't do another gum print for the rest of my life -- tho on the other hand, I think we most of us went through stuff like that until we got it out of our system and then settled into what seemed sensible & workable.

As for the issue of UV light in an ordinary bulb... Why do we dry our coated paper in the dark? Because light per se (UV schmoo Vee) will expose dichromated gum, more or less according to various variables. There were some things I forget now that just make gum arabic set... Like maybe cabbage patties, or particular ingredients in paint or paper. (If you have a copy of Ralph Mayer's "Materials of the Artist" -- a wonderful book with a ton of info, including good basic info about paint, media & pigments... Und, auf Deutsch, vieleicht Doerner. I always felt the Doerner I had in English wasn't quite translated from the German, but I was living in Switzerland & it was all I had, so I did what I could with it. In the original German he may be sublime.)

Also if you're using colors you've never used in gum printing before, expect surprises... PLUS each manufacturer has its own quirks, lies, shortcuts and utterly stupid additives. You don't know what they've put in the paint you're using. And even if it's just dry pigment... what volcano did they dig it out of? In other words, until you've worked out a palette, you'll probably suffer... (Tho I found that the Daniel Smith watercolors were generally OK ... True, dry pigments are cheaper & fewer mystery ingredients... tho they have at least as many mystery complications -- not to mention spilling and/or breathing them. )

So it sounds like you're suffering but still progressing (life should be so reliable). However, you might try regressing. I remember Demachy's story about how he learned gum printing from another customer at his photo shop, who said just mix a little paint with some gum arabic and spread it on, or like that. The tried & true primaries (magenta, thalo or prussian blue, & a nice yellow) are really all you need, and for what it's worth I never could control lamp black, but then nobody can... because there is no such thing: each one is different.

If, however, Pfritz, you really are doing "gum pigment ratio test" -- heh heh, I have a bridge you might be interested in buying... a special price, just for gum printers.