Re: haunted GUM (possible explanation found)
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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