U of S | Mailing List Archive | alt-photo-process-l | Re: Seeking Information on 2 problems with Gum process

Re: Seeking Information on 2 problems with Gum process

On Tue, 29 Apr 2008, cadunn wrote:
BUT, there are two areas where I need help and no one seems to mention it, no matter how meticulously they outline each process. (I'm working small -- 4.5 x 7 and using Arches Hot Press 140lb. because I like the smooth texture and finer detail possible with it, which I have achieved quite well with Cyanotypes.)

For any process where you wish to coat and expose the same piece of paper multiple times, what do people do with the severely uneven paper between exposures? I have preshrunk it and dried and ironed it before doing anything to it. But, once it is (perhaps sized depending on the process), coated,

Hi Claire, Wow! Congratulations on stumping everybody, first rattle out of the box !

Meanwhile, it could be something I've been doing -- or not doing or just didn't notice, but I never found that problem.

I did notice, however, and probably wrote somewhere that paper , like rust, never sleeps. So here are some points that occur to me. Or call them guesses (even educated guesses if you want to be kind).

Ironing the print before printing and developing may be part of the problem, because the heat and pressing effect could make something a different texture and shape than it would be naturally, hence a distortion at the outset, which even if you un-distort it, may not resume the original shape after wetting. That is, you're wetting it again, it probably REVERTS to its prior self, then re-forms at will.

I don't have a clear recollection of Arches hotpress, not having used it for years... A print of the small size you describe (snd I'm loving small now, too!) in one sense should have less stretch & shrink problem... but in another sense, as much or more because (as I noted previously) you examine it from closer on. Also you don't describe your pre-shrink procedure... I found, for what it's worth, that a VERY long pre-shrink in room temp water gives the same shrinkage as shorter in very hot, which could be easier for control purposes (not to mention energy).

HOWEVER, the humidity will always change your dimensions, no matter how religiously you preshrink, and as noted, in the small size the fine details get more scrutiny than otherwise. For instance EXTREMELY careful testers (not me, I promise) dried the paper being tested in humidity controlled conditions, and timed it -- and recoated and exposed at exactly the same point in the process !

However, ALL my tests showed that I could get a different measurement every time the paper dried, no matter how perfectly "shrunk," if drying time and room humidity weren't strictly controlled. So firstly I'd say test your shrinking: draw a line between two points on the paper, length and width (that's two lines of course). Measure them *precisely*... after all, as you point out, just a pencil width can make a detail blur if the paper changes.

Then consider strategies to be sure the dry paper dimensions are constant... and my hunch (tho I haven't tested it) would be that ironing may flatten but is a wild card otherwise, especially in the matter of size/humidity. And here I note that I found even a fancy custom made print frame wasn't evenly tight all over. (I wouldn't trust a one of them in fact -- they're OK for exposing in the wild, or even whatchamacallit -- um platinum printing... but not for recoating with the same neg.)

Which is to say, two sheets of plate glass (as shown in Issue # maybe 6 or 7 -- "Light Carpentry") with the print sandwich between and a couple of gallon jugs of liquid for weights on top gave much evener pressure. ($200 down the drain, but at least the water weights were free.)

I also found, for what it's worth, that the best drying method is to hang (drip dry) on a line, then if necessary flatten with standard weight. (What happens if you dry flat is that water puddles in the valleys making puddles and valleys and that's probably more destructive in small paper where scrutiny and examination are closer.)

You might also try this with a different paper... just a check, maybe the Arches is particular goosey in this respect (?)

More on pigment later... meanwhile, WELCOME to the list !


exposed, washed, and dried, it reverts to hills and valleys. And yes the
contact frame flattens out everything, and the large objects in the image appear nicely, but registration problems ensue in finely detailed areas. I need help!

My last nickels are for pigment. I've read much about pigments recently and assumed that folks would have made lists (as they have for just about everything under the sun, e.g., paper, emulsion proportions, etc.) Not so -- or at least I haven't found one. I found info on Lamp Black vs. Ivory Black, but so far nothing on other colors.)

Breaking the image up into CMY or CMYK indicates the use of 3 or 4 pigments respectively. What do people use for the best non-staining results? (I can tell you that Holbein Ultramarine Deep Watercolor gives excellent blue snow on sized paper! lol)

I realize that folks, and I will be one of these, like to shift things around depending on the image and the effect they are after, but for your basic palette-- what works??

I figure that folks expert in various processes have their arsenals of pigments and would know what works. Because I can't afford to experiment right now with things I have to buy, I'm asking for help.

And thank you very much in advance.