Re: Overexposeure was Re:Pinhole gums
Hi Diana, glad you made it home. I lived on an island during one of my former "lives" (a very happy one it was) and I know how life runs by the ferry schedule on an island.
Okay, I'm still not sure, so you're saying that all the prints that you had trouble with on that paper were printed in the same kind of weather, unusually cold and dry, or not? (Actually, I'm not sure it matters all that much, since you weren't printing outdoors, but in your humidified workspace, but just trying to cover all the bases.)
The other answer is disappointing :--) because I was hoping to rule something out, but if sometimes you could get a fully developed image by brushing and sometimes you couldn't, then it really makes no sense. We're fond of saying that almost anything that can be said about gum can be contradicted, but when we say that, all we mean is that gum is so versatile and flexible that the results are affected by many different variables and the interactions between them, and so different people working under different conditions and with different equipment/materials will have different observations about the particulars of how gum works. But while that's true, that the particulars of gum can vary from one practitioner to another, at the same time gum does behave lawfully under a particular set of conditions/protocol and should perform in a repeatable fashion within one printer's practice, everything being held reasonably constant.
If you could always develop an image by either long still-development or by brushing, then the logical conclusion would be that the problem is gross overexposure (then the next problem would be trying to understand the cause of the overexposure). If you could never obtain a fully-developed image by either long still-development or brushing, then the logical conclusion would be that the problem is either stain or (much less likely IME) an overall hardening of the gum layer, as Mark suggests. But if it's sometimes one and sometimes the other, then it's impossible to draw even tentative conclusions without more information. The only possible, though somewhat unlikely, explanation I can think of for this inconsistency might be that the weather varied during the period of time you were having difficulty printing on that paper, and under different weather conditions the overexposure was sometimes not as profound as at other times, making it possible to brush-develop the image during those times.
That said, I have to say that in all my years of printing gum, I have only twice seen gum so profoundly overexposed that the image could not be developed by long development or by brush-development. Once was when someone came to the door when I was exposing a print, and I left the print to answer the door and then forgot about it in attending to the business of the visitor, and the print exposed until the light burned out, a couple of hours at least. The other time was when I put a print frame on a black tarpaper roof on a hot sunny day and exposed in direct sun for five minutes. In both cases, I suspect it was more a thermal hardening issue than straight overexposure per se: the gum layer was hardened throughout by the heat that was generated in the print.
But those were both very extreme cases, and I'm not inclined to believe that overexposure this extreme could be caused by the conditions described here.
However, the explanation you seem to be satisfied with, that the gelatin "dried too quickly" makes no sense either.
It seems the word "drying" has been used in a confusing way in this discussion, which has served to conflate two different issues. You have two things going on: the gelatin setting up, and the paper/ gelatin drying. As the gelatin cools it becomes more solid than liquid, but that's not the same thing as the gelatin drying on the paper, which has to do with moisture content not temperature. Generally it doesn't matter how fast the gelatin dries once it's in the paper; the faster the better IME, because I don't like waiting all day for it. The garage where I hang my sized paper is "solar heated" by virtue of the fact it has no insulation and a metal roof, and on a sunny day the sized paper is often dry almost as soon as I hang it up. The quickness of the drying has no effect on the effectiveness of the size. The possible explanation offered, "the sizing dried too quickly, so it was as if the paper had no sizing at all" doesn't seem to me to be anchored in observable sizing reality. And if you mean the gelatin set up too quickly, then it makes even less sense, because when the gelatin sets up too quickly, you have a problem of too MUCH sizing, rather than not enough sizing.
That would be the most likely consequence of sizing outdoors on a cold dry day, as David and Chris suggested: the gelatin would set up so fast that it would spread on thick and viscous and sit on top of the paper rather than soaking in as a liquid, like it should. While this is a likely result of sizing outside in cold weather, I'm skeptical that this is the explanation for what we're dealing with here, for two reasons: (1) Diana says she didn't notice the gelatin setting up, and I would think you'd have to be awfully unobservant not to notice that. Since she scored a perfect score on the color discrimination test, I'm not inclined to describe her as unobservant. (2) the problems that getting the gelatin too thick and viscous would introduce in printing/development are different from the problems Diana describes. Yes, it might make the brush drag when coating, but the too-thick sizing would prevent any pigment staining problems, so staining wouldn't be an issue, and the too- thick sizing would be unlikely to be related to overexposure as well. What a proper sizing does is sink into the paper and leave the tooth open for the gum to cling to. A too-thick sizing, which is what you'd get if you brushed the sizing on too cool when it's already setting up, will clog up the tooth so the gum doesn't have anything to hang onto. So what happens when you're printing gum on a too-thick size layer like that, is that the gum won't adhere to the support and will flake off or slough off in development. That's obviously not what's happening here, so I don't think the gelatin cooling and setting up too fast is responsible for the problems Diana describes.
I did offer a kind of off-the-wall hypothesis about the gelatin evaporating off the paper in the cold dry wind. I have no idea if that's even possible, but if it were, at least it has the advantage of offering an explanation for Diana's problems, if it turns out that the problem is stain rather than overexposure. But it's a REEALLL long shot.
I'm inclined to think that the whole sizing thing may be a red herring, that the printing problems may be unrelated to the fact that the paper was sized on a cold dry day, but that's just conjecture on my part. Occam's Razor points that way, I think, because the only way to connect the sizing to it it is to come up with a new unsubstantiated theory, and I find things usually have a more accessible, sensible, logical, and evidence-based explanation when it comes right down to it.
I was working on a way of organizing variables to try to make sense of this, but had abandoned it while waiting for answers, hoping to rule out some variables at the outset. Now I'm tired and have rather lost heart for the enterprise; there are altogether too many unknowns in this equation.
Oh, one more thing, Diana: you seemed to be putting some stock in the fact that you were getting a faint printed out image after exposure. IME, that means nothing. Sometimes you get a faint one, sometimes a strong one, sometimes no printed out image at all; in my experience there is no connection between the presence or absence of a printed out image, or of how detailed it is, and the quality/ tonality of the image that eventually emerges from development.
Good night all, hope any of this is useful to anyone,
On Nov 30, 2008, at 4:29 PM, Diana Bloomfield wrote: