Re: haunted GUM (update)
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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