Phritz,
A bad batch of dichromate is definitely a possibility. If it is contaminated with Cr (III) salts, which you would not be able to tell with the visual inspection it would definitely act to cross-link gum on contact resulting in overall chemical fog. That is the easiest way to think of the phenomenon: a chemical fog. Everybody can relate to this from their earlier, traditional photography days. Another possibility is the way you size the papers, since you are using Cr(III) as a hardening agent. Maybe something changed in your sizing procedure. Do you soak the paper after it has been sized and seasoned to remove any Cr(III) that could act to cause chemical fog in the gum?
I have not been able to read and digest all the posts on the subject just yet.
Marek
> Date: Wed, 7 Oct 2009 15:22:41 +0200
> From: phritz-phantom@web.de
> Subject: Re: haunted GUM (update)
> To: alt-photo-process-l@usask.ca
>
> hi all,
> (quick recap:)
> i recently switched from ammonium dichromate to potassium dichromate,
> which i totally forgot. i think the pot-di is the most likely reason for
> the trouble i'm having right now. i did print gum with the pot-di before
> the mess, but this was on wood and canvas only, and i force-developed
> each layer with a brush. this is why i haven't noticed the new behavior
> earlier.
>
> 1st test strip (with explanation):
> http://i31.photobucket.com/albums/c367/phritz/burntsiena1gr.jpg
>
> this is with appr. 1gr of burnt siena (+ 5ml gum 16% + 5ml pot-di
> saturated). you can clearly see the tonal inversion with the shorter
> exposure times. on top there is a strip that was covered with cardboard
> (covering the whole thing widthwise), that received zero exposure. it is
> noticeably darker than the area that received 1min of exposure.
>
> similar result with lamp black (0.1gr)
> http://i31.photobucket.com/albums/c367/phritz/lampblack01gr.jpg
>
>
> expectedly the two ones with heavier pigment load did hardly develop at
> all, even after 2 hours. again tonal inversion and nothing coming off in
> the zero exposure areas.
> 2gr burnt siena:
> http://i31.photobucket.com/albums/c367/phritz/burntsiena2gr.jpg
> 1gr iron oxide black:
> http://i31.photobucket.com/albums/c367/phritz/ironoxideblack2gr.jpg
>
> here's a pic showing the thickness of the emulsions:
> http://i31.photobucket.com/albums/c367/phritz/coatings.jpg
>
>
> and i dug up and old test strip from about 2 months ago, with the same
> negative, same paper, same size, same mix of gum, same pigment... only
> with am-di. this mix was 1gr of lamp black +10ml gum/ 10ml am-di.
> exposure times start at 20sec and each grey scale gets +20 sec, so it's
> from 20 sec to 3:00 min.
> http://i31.photobucket.com/albums/c367/phritz/oldemulsion.jpg
>
>
> i will try different papers and gum and pot-di in various strengths
> next. hopefully there is a way out of this mess.
> if anyone can offer some hints or ever experienced something similar ,
> it would be very much appreciated.
> thanks,
> phritz
>
> ps.
> judy, i will check out the archives and PF later today.
>
>
> phritz phantom schrieb:
> > paul,
> > unfortunately i printed the negative, the one shown in the second pic.
> > that caught me completely off-guard and i took me a day to realize
> > what happened. it took a quick look first and it looked normal with a
> > lot of stain, then later i suddenly realized it.
> >
> > there is definitely something fishy.... i printed all the test strips
> > this evening and i constantly get the tonal inversion. although not as
> > extreme as the first time. AND another thing i consistent: no exposure
> > - no pigment coming off at all.
> >
> > another thing just dawned on me: those are the first gum prints i made
> > with the new batch of potassium dichromate. i've only used ammonium
> > before. i totally forgot that i mixed up a fresh solution about two
> > weeks ago. i think this is the first time i'm using it. most likely
> > it's the dichromate that is somehow responsible for this mess. i'm
> > using saturated solutions, so the exposure time should go up
> > naturally. it still doesn't explain the severe tonal inversion and stuff.
> > is pot-di more prone to fogging (from room light)? maybe this is some
> > kind of solarisation, i'm having here.
> > i've never been especially careful about room light, but i never had
> > problems before. i coat with the lights on, then dry in the dark, but
> > i occasionally turn on the lights for a minute or two, when i need to
> > use the bathroom (this is where the drying takes place).
> > maybe the pot-di is on the phritz (!!) alltogether?
> >
> > also i will try a different paper and a new mix of gum. maybe the gum
> > solution is foul.
> > the test strips are drying now, i will scan and post them online
> > tomorrow.
> >
> > phritz
> >
> >
> >
> > Paul Viapiano schrieb:
> >> phritz...
> >>
> >> The inversion you're seeing is weird, a positive of that chart will
> >> always print with black text on white.
> >>
> >> But you're printing the positive, right...you never inverted it to
> >> print?
> >>
> >> NOw, there's inversion that K speaks of on her site but that is not
> >> TOTAL inversion, just a reversal of the high tones usually because of
> >> gum/pigment ratio. I've experienced this once on a test strip. I
> >> added gum and it was fine.
> >>
> >> But a TOTAL reversal as you are claiming...well, I've never heard of
> >> that at all.
> >>
> >> Are you absolutely positive (no pun intended) that you exposed the
> >> correct digital charts?
> >>
> >> p
> >>
> >>
> >>
> >>
> >> ----- Original Message ----- From: "phritz phantom"
> >> <phritz-phantom@web.de>
> >> To: <alt-photo-process-l@usask.ca>
> >> Sent: Tuesday, October 06, 2009 10:10 AM
> >> Subject: Re: haunted GUM (related to judy's favourite pet peeve: the
> >> pigment ratio test)
> >>
> >>
> >>> dear katharine,
> >>> yes, this is my main source of confusion. i was experimenting with
> >>> higher pigment loads. i made three layers of yellows and reds (for
> >>> the highlights) and then wanted to add the shadows. i mixed up a
> >>> stong emulsion (the 2.5gr blue black one) and thought that the worst
> >>> thing to happen is that the layer just washes off and i can do it
> >>> again. i tried the heavy load to check the limits of the process, to
> >>> see how far i can go with the pigment concentration. the layer not
> >>> dissolving at all, that i was not prepared for.
> >>> i did this twice (i saved the excess emulsion from the first
> >>> coating). at first a 2:30 exposure and a 2-3h development, the last
> >>> hour in hot water (appr. 40°c/ 100°f), then i had enough and brushed
> >>> it all off. dried overnight and painted on the same emulsion the
> >>> next day. this time with only 1min exposure. same result. no
> >>> flaking, the emulsion did not move at all. also when forcing the
> >>> development with a brush, i did not see the usual high-contrast
> >>> image (the highlights coming off before the shadows which got lots
> >>> of light), it just came off all at once.
> >>>
> >>> then i coated the test sheet with the 1.2gr of iron oxide. and saw
> >>> the pigment in the unexposed area behave the same way as the
> >>> emulsions before. this makes me assume that there is some kind of
> >>> connection. i just don't know which one.
> >>> ....
> >>> i just wanted to type that the test sheets "printed with a lot of
> >>> stain, but in a way like i expected them to", then i started
> >>> wondering why the "stain" is happening in the areas that should be
> >>> pitch-black, because they are in the clear areas of the
> >>> transparency. now, i went and had another look at those and saw that
> >>> they are completely INVERSED. i printed negatives from a negative (i
> >>> did NOT forget to inverse the scale in photoshop).
> >>> here are the scans:
> >>> http://i31.photobucket.com/albums/c367/phritz/threestrips.jpg
> >>>
> >>> the one on the left and the one in the middle got 1min exposure (all
> >>> three scales the same) from my sunlamp. the one on the right got
> >>> 10min of desk lamp.
> >>>
> >>> here's the proof for the inversion:
> >>> http://i31.photobucket.com/albums/c367/phritz/P1010035.jpg
> >>>
> >>> i think i'm losing my marbles here... we'll see how the test strips
> >>> from today will print.
> >>>
> >>> phritz
> >>>
> >>>
> >>> Katharine Thayer schrieb:
> >>>> phritz, you've got the right idea about different pigments
> >>>> requiring different amounts to achieve a color-saturated layer;
> >>>> pigments vary widely in pigment strength, as you're learning.
> >>>> Most earth pigments, like your burnt siena, are quite weak as
> >>>> pigments go, so it's not surprising that you don't get an opaque
> >>>> coating with a fair amount of burnt siena (also, some burnt sienas
> >>>> are quite transparent).
> >>>>
> >>>> The main comment I want to make in a hurry is that underexposure is
> >>>> not likely your problem. If your strip were "severely
> >>>> underexposed" the gum coating would dissolve into the water within
> >>>> a few minutes, leaving you a piece of white paper to dry and try
> >>>> again. Since you have it even where there's no exposure, that
> >>>> suggests stain rather than overexposure as the source of the
> >>>> problem. Also, where you've wiped off the bulk of the pigment
> >>>> layer on the area that received no exposure, there's still
> >>>> significant stain left (that grainy deposit, that's pigment
> >>>> stain.) Too much pigment, it looks almost certainly.
> >>>>
> >>>> But there are a couple of things that don't make sense to me, so
> >>>> maybe a clarification: I'm reading that this is one part of a
> >>>> sheet you coated and tore into three pieces, and the other two
> >>>> pieces printed fine? Could we see those? It doesn't make sense
> >>>> that with two parts of the same coating on the same paper it
> >>>> printed fine and with one part there was serious stain, so maybe
> >>>> I'm not understanding your description/example/question.
> >>>>
> >>>> But definitely not underexposed, if you've got heavy tone like that
> >>>> that won't go away in 20 minutes of development.
> >>>>
> >>>> There's an example with lamp black on my pigment stain page that
> >>>> looks a lot like yours, down towards the bottom of the page,
> >>>> compared to how it prints with half the amount of pigment. (third
> >>>> visual down on the page).
> >>>>
> >>>> http://www.pacifier.com/~kthayer/html/stain.html
> >>>>
> >>>> Hope any of that is helpful
> >>>> Katharine
> >>>>
> >>>>
> >>>>
> >>>> On Oct 5, 2009, at 4:28 PM, phritz phantom wrote:
> >>>>
> >>>>> hi all,
> >>>>>
> >>>>> my gum is acting strange again. the only reason i can think of is
> >>>>> an increased pigment load.
> >>>>> my standard pigment is lamp black, which is a very strong pigment.
> >>>>> 0.5gr are enough for a very thick and opaque layer (before
> >>>>> exposure). since i was used to this strong pigment, i was
> >>>>> generally using too little pigment for all the other colors,
> >>>>> resulting in very thin layers. so, i made a comparison sheet with
> >>>>> dabs of all the different pigments (all are powder pigments) in
> >>>>> various strengths. i was quite surprised to see that for example
> >>>>> 2gr (+5ml gum + 5ml saturated pot-di) of my burnt terra di siena
> >>>>> produces a coating that is neither thick, nor opaque.
> >>>>>
> >>>>> at first everything went fine, then suddenly a very thick blue
> >>>>> black coating (1,5gr iron oxide black + 1gr phthalo blue +5ml gum
> >>>>> + 5ml pot-di) didn't come off at all during development. ok, i
> >>>>> thought the reason was that i increased the exposure time as well
> >>>>> to compensate for the bigger amount of pigment. later: the same
> >>>>> with a short exposure of 1 minute. the next day: again, with a
> >>>>> layer with 2gr of burnt siena.
> >>>>>
> >>>>> it was time to search for errors. i coated a sheet with 1,2gr of
> >>>>> iron oxide black (not my favourite pigment), again with 5ml gum +
> >>>>> 5ml pot-di, ripped it in three parts and made a comparison of the
> >>>>> two different sheets of glass i use as printing frames and put
> >>>>> the third one for 10min under the desk lamp that i often use
> >>>>> during registration and such. the first two printed fine and
> >>>>> pretty much the same. but with the third one, i noticed something
> >>>>> strange. not only that there seems to be some uv present in the
> >>>>> light of the desk lamp, but also: i left part of the sheet covered
> >>>>> and it received zero exposure. and this part stayed completely
> >>>>> black, not a whiff of pigment came off in the appr. 20min of
> >>>>> development.
> >>>>>
> >>>>> here's a scan of the test strip:
> >>>>> http://i31.photobucket.com/albums/c367/phritz/teststrip.jpg
> >>>>>
> >>>>> the part on top with the white stripe received ZERO exposure. i
> >>>>> scratched off a little bit to show that the pigment is wet and
> >>>>> soaked. it can be removed, it just doesn't want to come off on its
> >>>>> own (nor did i have any success with brushing or sprinkling of
> >>>>> water, only nothing or everything comes off)
> >>>>> i'm sure this is somehow related to my problems. i'm just getting
> >>>>> too confused here. it probably means that my images were severely
> >>>>> underexposed. i did extensive testing for negative colors lately
> >>>>> and determined with a step wedge (unfortunately not a stouffer
> >>>>> one) that my minimum print time is 50seconds. i printed the thick
> >>>>> layers with up to 2:30min. still nothing.
> >>>>>
> >>>>> (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?
> >>>>> thanks,
> >>>>> phritz
> >>>>>
> >>>>
> >>>>
> >>>
> >>
> >>
> >>
> >
> >
> >
>
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