Re: Rethinking pigment stain

This one got bounced back from usask, so I'm trying to send it again,
since others of mine have got through since then:

On Dec 15, 2005, at 9:18 AM, Katharine Thayer wrote:

> Well, technically and theoretically, of course that's true, but in a
> practical sense it is largely a function of humidity how much
> crosslinking occurs over a specified period of time as a result of the
> "dark reaciion," which theoretically starts as soon as the coating is
> applied. The graph I have for the dark reaction in dichromated gum
> arabic shows the line crossing time 0 at about 85% humidity, but the
> variable on the other dimension is not very well defined: "time
> required for the reaction between the dichromate and gum arabic to
> reach the same degree of completion." Since we don't know
> quantitatively what that degree of completion is, all the graph tells
> us is that there is a very steep relationship between humidity and
> speed of the reaction. At any rate, whatever that "degree of
> completion" is, it takes 0 hours to get there at 85% humidity, and 145
> hours to get there at 45% humidity.
>
> Katharine
>
>
> On Dec 15, 2005, at 4:16 AM, Yves Gauvreau wrote:
>
>> If, as some of you said, you leave a fresly coated layer of gum
>> emultion
>> over night in the dark or best condition and it's showing something
>> that
>> shouldn't be there the next day. I would say there is "ALWAYS" a
>> little
>> something even if it's not visible to the naked eye. There will be
>> some
>> molecules that change "form" just in the time it takes to dry the
>> emultion,
>> call it fog, stain, noise, global insolubilisation, etc, I don't
>> really care
>> about the name but you can be sure of one thing it's always there,
>> visible
>> or not.
>>
>> Yves
>>
>>
>>
>> ----- Original Message -----
>> From: "Katharine Thayer" <kthayer@pacifier.com>
>> To: <alt-photo-process-l@sask.usask.ca>
>> Sent: Wednesday, December 14, 2005 9:49 PM
>> Subject: Re: Rethinking pigment stain
>>
>>
>>> On Dec 14, 2005, at 1:36 PM, Tom Sobota wrote:
>>>
>>>> I was commenting on Dave's opinion that '"fog" is a misleading
>>>> term',
>>>> which implies that we pretty much _don't_ all agree on what fog is.
>>>
>>> Fair enough; I was reading Dave's remark to mean simply that he
>>> didn't
>>> think fog was often encountered in usual practice with gum, a remark
>>> I
>>> agree with, but yours is a more literal and for all I know more
>>> accurate reading.
>>>
>>>>
>>>> As my use of "global insolubilization", it means the following:
>>>
>>> I didn't say I didn't understand it; "global insolubilization" pretty
>>> much defines itself. I just said I found it an awkward mouthful,
>>> meaning not a very graceful phrase, and I wouldn't be likely to use
>>> that particular verbal construction myself, as it seems ugly to me
>>> in
>>> a prosodic sense, quite apart from its meaning, much like the
>>> bureaucratic words like "eligibilize" etc.
>>>
>>> But on reflection, I find I don't even agree with the phrase as a
>>> good
>>> definition for fog. While there are some types of fog, such as the
>>> dark
>>> reaction, that will probably always present as a global
>>> insolubilization, there's no particular reason why inadvertent
>>> exposure
>>> can't affect a part of the coating without the entire thing being
>>> fogged, or that it can't crosslink enough of the gum to partially
>>> harden the coating without rendering it completely insoluble.
>>>
>>> I'm going to make a liar out of myself now by recalling a second
>>> example of fog from my own experience, after I said I'd only seen it
>>> once, but one can't remember everything all the time, especially when
>>> you're as old as I am and have as many things to remember as I have.
>>> At
>>> any rate, one time a stray ray of weak sunshine found its way
>>> between
>>> the pine trees and the garage and the guest cottage and the house
>>> into
>>> the studio to cast onto the drying table a dim shadow of the
>>> windowframe, so dim I didn't even notice it as I was drying the
>>> coating. But it had already printed itself into the coating, and
>>> spoiled the subsequent print. I would call this fog. It was
>>> inadvertent formation of crosslinked gum, but it certainly wasn't
>>> global insolubilization (not only did it only affect the parts of the
>>> coating that the sunlight actually fell on, but the intentional
>>> print
>>> printed on top of it, so the gum obviously wasn't completely
>>> insolubilized, even in the areas where the coating was fogged.
>>>
>>> So I'm going to stick with my wording, not only because I like the
>>> sound of it better, but because it means exactly what I mean by fog,
>>> and "global insolubilization" does not. But perhaps I should
>>> specify, though it seems to me it should go without saying, that I am
>>> not imposing my definition on you or anyone else, just telling you
>>> why
>>> it's the one I will use myself, personally.
>>>
>>>>
>>>>
>>>> This is the term I prefer, but I'm not imposing it upon anyone,
>>>> so if you want to say "inadvertent (meaning non image-related)
>>>> formation of crosslinked gum" instead of "global insolubilization",
>>>> that's just fine with me. I would only object on the use of
>>>> 'inadvertent'
>>>> as a synonymy for 'not image-forming'. But hey ...
>>>
>>> Actually, I said "not image-related" rather than "not image-forming."
>>> inadvertent means "not intentional," meaning not related to the image
>>> that is being intentionally printed. But fog can certainly be
>>> image-forming, as in the case of the image of the shadow of the
>>> windowframe that printed itself perfectly onto my print.
>>>
>>>>
>>>> Again, whether fog happens more or less frequently in actual
>>>> practice is not an impediment for having a definition for it, in my
>>>> opinion.
>>>>
>>>
>>> I agree; earlier today I thought we all pretty much agreed on a
>>> definition, but now I see that we don't.
>>>
>>> Katharine
>>>
>>>
>>>>
>>>> At 17:43 14/12/2005, you wrote:
>>>>> I think we pretty much agree on what fog is, although I would never
>>>>> use the phrase "global insolubilization;" that seems a rather
>>>>> awkward
>>>>> mouthful to me. I'll continue to use the phrase I've been using;
>>>>> to
>>>>> me fog is the inadvertent (meaning non image-related) formation of
>>>>> crosslinked gum, and, as I said in my response to Joe's lexicon
>>>>> last
>>>>> week or whenever that was, in my mind it includes the dark
>>>>> reaction.
>>>>> I don't know about the "continuing reaction" I've never seen that
>>>>> myself.
>>>>>
>>>>> I thought Dave's point was, how often do we ever see fog in actual
>>>>> practice? I've only seen it once, when I left a coated paper
>>>>> sitting
>>>>> by a window and went off to get something. And I've only seen fog
>>>>> in
>>>>> the form of the dark reaction once, when I deliberately left
>>>>> coated
>>>>> paper in the dark to see if it would happen (it did), but I've
>>>>> never
>>>>> seen it in practice, because I always coat and dry one paper at a
>>>>> time and expose immediately.
>>>>> Katharine
>>>>>
>>>>>
>>>>>
>>>>> On Dec 14, 2005, at 7:08 AM, Christina Z. Anderson wrote:
>>>>>
>>>>>> Right on, Tom,
>>>>>>
>>>>>> fog = global insolubilization of the gum layer...
>>>>>>
>>>>>> I'll add to your list one thing they used to say but I have never
>>>>>> found to
>>>>>> be true is they used to say certain pigments produced as they
>>>>>> termed
>>>>>> it
>>>>>> "spontaneous insolubilization of the gum".
>>>>>>
>>>>>> I could say that when I was doing 8 large gums at once down in
>>>>>> South
>>>>>> Carolina where the humidity was higher, the last print to go into
>>>>>> the water
>>>>>> would take longer development to remove nonimage "fog". Fog, up
>>>>>> to a
>>>>>> certain point in gum practice, usually doesn't make too much
>>>>>> difference
>>>>>> because it is removable, unlike silver gelatin.
>>>>>>
>>>>>> Does this fog, then, form an umbrella over the two terms of "dark
>>>>>> reaction"
>>>>>> and "continuing action"? Because both result in global, non-image
>>>>>> insolubilization. In other words, back in "the day"
>>>>>> (1800's-1900's)
>>>>>> they
>>>>>> didn't term it fog in the first place but used these two terms to
>>>>>> describe
>>>>>> this global insolubilization.
>>>>>> chris
>>>>>>
>>>>>>> It all depends on how you define 'fog'. To me, fog is a global
>>>>>>> hardening or insolubilization of the gum-dichromate layer which
>>>>>>> does not contribute to the formation of an image.
>>>>>>>
>>>>>>> It can be produced by any (or a sum of) several causes, among
>>>>>>> which
>>>>>>> accidental exposure to light too, of course. Others are heat,
>>>>>>> exposure
>>>>>>> to chemicals, and the simple passing of time. Surely others.
>>>>>>>
>>>>>>> The normal exposure to light of a layer of dichromated gum under
>>>>>>> a negative produces a hardening which is not physically different
>>>>>>> from a fog-producing exposure to light, but it produces an usable
>>>>>>> image
>>>>>>> since it is not global but rather differential. So we don't call
>>>>>>> it
>>>>>>> fog.
>>>>>>>
>>>>>>> This loose definition of fog could be applied to silver-gelatin
>>>>>>> emulsions
>>>>>>> too, actually.
>>>>>>>
>>>>>>> Pigment stain is different, and perhaps unique to gum, carbon and
>>>>>>> other processes using finely ground particles of pigment.
>>>>>>>
>>>>>>> But dichromate stain has a sort-of analogue in silver-gelatin
>>>>>>> emulsions
>>>>>>> when you develop with pyrogallol or pyrocatechol, for example,
>>>>>>> which
>>>>>>> also produce stain. This stain contributes to the image, however,
>>>>>>> because
>>>>>>> it is in the negative and not in the positive.
>>>>>>>
>>>>>>> If you want to see fog in gum, coat a paper and keep it in the
>>>>>>> dark
>>>>>>> for a
>>>>>>> week or two in a warm place. Then develop side by side with a
>>>>>>> just-prepared emulsion. The relative darkening of the older coat
>>>>>>> should
>>>>>>> be evident.
>>>>>>>
>>>>>>> Tom Sobota
>>>>>>> Madrid, Spain
>>>>>>>
>>>>>>>
>>>>>>> At 03:38 14/12/2005, you wrote:
>>>>>>>> I don't know all the details regarding that past discussion,
>>>>>>>> but I
>>>>>>>> think
>>>>>>>> "fog" is a misleading term. I consider fog to be accidental
>>>>>>>> exposure,
>>>>>>>> e.g.
>>>>>>>> someone opens the back of a 35mm camera and the film gets
>>>>>>>> "fogged".
>>>>>>>> Perhaps
>>>>>>>> gum paper can get fogged from ambient light levels being too
>>>>>>>> high
>>>>>>>> in the
>>>>>>>> darkroom, but I've never had that problem.
>>>>>>>>
>>>>>>>> Dave Rose
>>>>>>>> Powell, Wyoming
>>>>>>>>
>>>>>>>> ----- Original Message -----
>>>>>>>> From: "Katharine Thayer" <kthayer@pacifier.com>
>>>>>>>> To: "alt photo" <alt-photo-process-l@sask.usask.ca>
>>>>>>>> Sent: Tuesday, December 13, 2005 12:16 PM
>>>>>>>> Subject: Rethinking pigment stain
>>>>>>>>
>>>>>>>>
>>>>>>>>> Hi gum printers,
>>>>>>>>> Because for most of my gum printing career I've printed on
>>>>>>>> unsized
>>>>>>>>> paper, I developed a definition of pigment stain that I realize
>>>>>>>> now
>>>>>>>>> probably applies mainly, if not exclusively, to printing on
>>>>>>>> unsized
>>>>>>>>> paper. My definition required that in order for something to
>>>>>>>>> be
>>>>>>>> called
>>>>>>>>> pigment stain, the pigment had to penetrate the paper and be
>>>>>>>> indelible.
>>>>>>>>> And in my experience, when pigment stain occurred, it
>>>>>>>>> occurred
>>>>>>>>> immediately when the coating was applied; if the pigment was
>>>>>>>> excessive
>>>>>>>>> in relation to the gum, it would stain the paper immediately on
>>>>>>>>> application.
>>>>>>>>>
>>>>>>>>> The tonal inversion thing made me rethink that idea, as I said
>>>>>>>>> a
>>>>>>>> couple
>>>>>>>>> of days ago, and after doing some experiments with sized and
>>>>>>>> unsized
>>>>>>>>> paper, I've decided I need a more inclusive definition that
>>>>>>>>> incorporates what happens on sized paper, or maybe two
>>>>>>>>> different
>>>>>>>> terms;
>>>>>>>>> I haven't decided yet for sure.
>>>>>>>>>
>>>>>>>>> A more inclusive definition for "pigment stain" would say that
>>>>>>>> pigment
>>>>>>>>> stain is whenever you get pigment in places where it shouldn't
>>>>>>>> be,
>>>>>>>>> such as in unexposed areas of an image or step print. Whether
>>>>>>>> or not
>>>>>>>>> that out-of-place pigment forms an indelible *stain* will be a
>>>>>>>> function
>>>>>>>>> of how well the paper is sized. On sized paper, this "stain"
>>>>>>>> will wipe
>>>>>>>>> off easily, whereas on unsized paper it will be indelible, but
>>>>>>>>> in
>>>>>>>>> either case, you've got pigment you don't want in areas that
>>>>>>>> should be
>>>>>>>>> very light or paper white, hence: stain.
>>>>>>>>>
>>>>>>>>> One problem with this more inclusive definition is that it
>>>>>>>> doesn't
>>>>>>>>> distinguish between stain and fog. Someone referred recently
>>>>>>>>> to
>>>>>>>> a
>>>>>>>>> discussion from last summer where Mark showed a gum test print
>>>>>>>> where
>>>>>>>>> there was color on areas where the print should have been paper
>>>>>>>> white.
>>>>>>>>> I called that stain, and was told that it was fog. I conceded
>>>>>>>> the
>>>>>>>>> point; when told that it could be wiped off the paper I assumed
>>>>>>>> (given
>>>>>>>>> my then understanding of stain) that it couldn't possibly be
>>>>>>>> stain and
>>>>>>>>> must be fog, although I didn't have a clear understanding of
>>>>>>>> what could
>>>>>>>>> have caused the fog. And when that was brought up recently, I
>>>>>>>>> acknowledged I'd been wrong when I'd called it stain. But now
>>>>>>>> that I
>>>>>>>>> have seen for myself that pigment stain can also be easily
>>>>>>>>> wiped
>>>>>>>> off
>>>>>>>>> sized paper, (while still wet, of course) I'm not sure I know
>>>>>>>> how to
>>>>>>>>> tell the difference between stain and fog on sized paper.
>>>>>>>>>
>>>>>>>>> They are of course different in substance, because what I would
>>>>>>>> call
>>>>>>>>> "pigment stain" is just pigment, since it occurs in areas
>>>>>>>>> where
>>>>>>>> no
>>>>>>>>> exposure, and therefore no formation of crosslinked gum, has
>>>>>>>> occurred,
>>>>>>>>> whereas fog, in my opinion, would involve the formation of
>>>>>>>> crosslinked
>>>>>>>>> gum.
>>>>>>>>>
>>>>>>>>> On unsized paper, excess pigment impregnates the paper as
>>>>>>>> stain, and
>>>>>>>>> that's why it stays with the paper rather than dissolving away
>>>>>>>> with the
>>>>>>>>> dichromate and soluble gum from unexposed areas. But on sized
>>>>>>>> paper,
>>>>>>>>> even though the pigment isn't held in the paper as stain, or in
>>>>>>>>> crosslinked gum as "tone" it still remains on the paper in
>>>>>>>> unexposed
>>>>>>>>> areas, as seen in the examples of "tonal inversion." This is
>>>>>>>>> interesting, but puzzling, to me. At any rate, I've satisfied
>>>>>>>> myself,
>>>>>>>>> by cutting coated papers in half and exposing one side and
>>>>>>>> putting the
>>>>>>>>> other side directly into water, that the "pigment stain" is
>>>>>>>>> the
>>>>>>>> same
>>>>>>>>> on unexposed areas of exposed coatings as it is on completely
>>>>>>>> unexposed
>>>>>>>>> paper, whether sized or unsized, which makes me even more
>>>>>>>> confident
>>>>>>>>> that the effect has nothing to do with exposure, heat or
>>>>>>>> anything else
>>>>>>>>> related to the exposure itself, but is simply pigment stain.
>>>>>>>>>
>>>>>>>>> Thoughts, anyone? I will soon be revising my page on stain,
>>>>>>>>> lord
>>>>>>>>> willing and the creek don't rise, to reflect the evolution of
>>>>>>>>> my
>>>>>>>>> thinking on this topic.
>>>>>>>>> Katharine
>>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>
>>>>
>>
>
Received on Thu Dec 15 19:50:26 2005