RE: Gum hardening: top down experiment

Dave,

And it works exactly that way in Carbon. If the exposure is too short
we can "try" to save the print by developing for a shorter period of
time, then "set" the gelatin in very cold water. If exposure is too
short we develop for a longer period of time, and/or increase the
temperature of the water.

For testing I would settle on a set exposure time. The problem here,
none of the other parameters are fixed so what exposure time should
you try?

Sandy

>Oh, in that case yes, it must be underexposure then. I think you need an
>exposure that can take at least full development (or nearly full because it
>is hard to define what is full). If exposure is too short but we "save" it
>but developing short, then it is hard to make judgement on what we are
>trying to test for this case. Saving the print might work for actual prints,
>of course.
>
>Dave S
>
>
>-----Original Message-----
>From: Marek Matusz [mailto:marekmatusz@hotmail.com]
>Sent: Tuesday, April 11, 2006 1:48 PM
>To: alt-photo-process-l@usask.ca
>Subject: RE: Gum hardening: top down experiment
>
>Sandy,
>The piece did not fade as such, the esposed gum layer was so soft it started
>running down the transparency once I hanged it to dry. Actually it developed
>so fast, I pulled it out from the water too late. Somebody else was right
>here, you really can not arrest gum development as it is soluble in cold
>water as well.
>I will try more exposure.
>Marek, Houston
>
>>From: Dave Soemarko <fotodave@dsoemarko.us>
>>Reply-To: alt-photo-process-l@usask.ca
>>To: alt-photo-process-l@usask.ca
>>Subject: RE: Gum hardening: top down experiment
>>Date: Tue, 11 Apr 2006 12:56:23 -0400
>>
>>Perhaps "a piece of ice" might not be a good analogy. A piece of
>>dampened spongue might be closer.
>>
>>Dave
>>
>>-----Original Message-----
>>From: Dave Soemarko [mailto:fotodave@dsoemarko.us]
>>Sent: Tuesday, April 11, 2006 12:30 PM
>>To: alt-photo-process-l@usask.ca
>>Subject: RE: Gum hardening: top down experiment
>>
>>It might be because the development is not complete, so there is still
>>a lot of unhardened gum (which contains water). Well, actually even the
>>hardened gum is soaked up with water at that point, so the water will
>>continue to develop the surrounding gum. Sort of like if you put a
>>piece of ice on jello versus you put a piece of ice on gum. The first
>>case will have no problem whereas the second will make a mess.
>>
>>
>>Dave
>>
>>
>>-----Original Message-----
>>From: Sandy King [mailto:sanking@CLEMSON.EDU]
>>Sent: Tuesday, April 11, 2006 12:19 PM
>>To: alt-photo-process-l@usask.ca
>>Subject: RE: Gum hardening: top down experiment
>>
>>
>>Dave,
>>
>>You make some good points.
>>
>>Just a couple of follow-up comments.
>>
>>I know that gum will continue to develop in cold water, but my
>>understanding was that Marek's print was removed from the water and
>>hung up to dry. If that is so, I am still confused as to why it would
>>fade.
>>
>>Sandy
>>
>>
>>
>>
>>
>> >Hi Katharine, Marek, Sandy, Judy, and whoever interested,
>> >
>> >Thanks for your efforts and sharings on your findings.
>> >
>> >About the tests, however, I have a few suggestions:
>> >
>> >Katharine, you probably shouldn't expose longer than usual and expose
>> >the front and back differently because that will affect interpretation.
>> >Let's try to step back and look at our hypothesis first. Let's say we
>> >assume that hardening is from top to bottom (we don't have to agree
>> >on this, but we can take any view and start from there). The test
>> >then, is to expose it not too much from both side. If hardening is
>> >from top to bottom, the one exposed from the front will not reached
>> >the base, so it has nothing to hold on, so it will flake off, whereas
>> >the one exposed from the back will grab the base, so it will have
> > >some image. But if expose a lot (or strongly), then probably both
>> >will have an image because even the one exposed from the front will
>> >be exposed sufficiently to reach the base. Now the contrast of the
>> >two might be different, and so we might start to make different
> > >inference from there,
>>but that is not the original goal of the test.
>> >
>> >Suppose that we expose it normally, and get a fine image for the one
>> >exposed from the back but not for the one exposed from the front, we
>> >pretty much proved our hypothesis. But suppose we don't get an image
>> >from either one, then we need to adjust. It might be that the mylar
>> >might be cutting off a lot of UV, so we need to expose more. But if
>> >we expose more, is it a fair comparison because the front one doesn't
>> >have
>>the
>>UV blocking by the mylar?
>> >So in order to have a reasonable test, we need to increase expose but
>> >also cover the front side by a piece of mylar during exposure.
>> >
>> >Our tests seem to be something in between. The fact that the image
>> >continue to dissolve after development seems to suggest that exposure
>> >is not enough so there is still a lot of unhardened gum (Sandy, to
>> >answer the question of why this is happening in gum but not in
>> >carbon, the difference in mechanism is that gelatine doesn't dissolve
>> >in cold
>>water
>>whereas gum does).
>> >
>> >My suggestion would be to expose perhaps a step tablet with double
>> >the amount of time used for exposing through the back, but when
>> >exposing the front, cover it with a piece of mylar.
>> >
>> >And thank you again for all your efforts. I am by no means asking you
>> >to
>>do
>> >a certain test. It is simply a suggestion from me, a lurker now. :-)
>> >
>> >
>> >Dave
>> >
>> >-----Original Message-----
>> >From: Katharine Thayer [mailto:kthayer@pacifier.com]
>> >Sent: Tuesday, April 11, 2006 11:22 AM
>> >To: alt-photo-process-l@usask.ca
>> >Subject: Re: Gum hardening: top down experiment
>> >
>> >Marek, thanks for your response. My patience for this discussion was
>> >coming to an end just as your post popped into my mailbox; you have
>> >revived me. A couple of comments embedded below:
>> >
>> >
>> >On Apr 11, 2006, at 7:41 AM, Marek Matusz wrote:
>> >
>> >> Katharine,
>> >> I was very impressed with your results and thanks for contributing
>> >> to this discussion in a positive and constructive way. Looking at
>> >> your scans I would conclude that heavily pigmented gum layers on
>> >> unabsorbant substrate do harden from the top down, just like other
>> >> dichromated colloids.
>> >> I see very nice tonal gradations in the print exposed from the bottom.
>> >> The three variables (gum, dichromate and pigment ratios) are not
>> >> optimised, but at this point I am looking for illustration of
>> >> principles, rather then perfect prints.
>> >
>> >Thanks, I agree.
>> >
>> >> I did a similar experiment last night. I coated a heavily
>> >> pigmented and thick layer of gum on a transparency material that I
>> >> use to print diginegatives (HP brand). This brand has a nice sandy
>> >> feel to it, so I though it would help to hold the gum. I exposed
>> >> coated pieces for
>> > > twice my usual times, one through top, the other from the bottom.
>> >
>> >For whatever it's worth, I exposed the front-exposed print on mylar
>> >for
>> >6 minutes, which is 4X my usual time for that negative, and the
>> >back-exposed print for twice the time of the front-exposed one (12
>>minutes).
>> >
>> >> The piece exposed from the top flaked off rather quickly leaving
>> >> no image. The was no image that I could see at any point. The piece
>> >> exposed thorough the bottom once in the water started behaving like
>> >> a carbon print, where the colloid was dissolving in water, rather
>> >> then flaking off. After about 3 minutes I was excited to see a full
>> >> tonality image, with beautiful tonal gradations. Unfortunately the
>> >> image continued to develop even afet I took it out of water and
>> >> hanged it to dry.
>> >
>> >This is exactly what happened with the front-exposed print in my
>> >experiment; it looked okay, although very high-contrast, when I took
> > >it out of the water, but by the time it was dry the hardened gum had
>> >melted and puddled on the mylar. (This is not what usually happens
>> >when I print on scuffed mylar using a more normal emulsion).
>> >
>> >
>> >
>> >> This morning there was only a faint image left on the piece of
> > >> transparency. I will give it another try with much longer exposure
>> >> and perhaps lower dichromate to get more depth of UV penetration
>> >> and hardening and higher Dmax.
>> >>
>> >
>> >I look forward to your report,
>> >Katharine
>> >
>> >
>> >
>> >>> From: Katharine Thayer <kthayer@pacifier.com>
>> >>> Reply-To: alt-photo-process-l@usask.ca
>> >>> To: alt photo <alt-photo-process-l@sask.usask.ca>
>> >>> Subject: Gum hardening: top down?
>> >>> Date: Mon, 10 Apr 2006 11:33:03 -0700
>> >>>
>> >>> Okay, I've coated a very thick, very heavily-pigmented gum
>> >>> emulsion on mylar and printed it from the front and from the back.
>> >>> A couple of comments before I give you the URL:
>> >>>
>> >>> (1) though the emulsion was very heavily pigmented, two things
>> >>> resulted in not a very deep DMax: (a) the fact that I used ivory
>> >>> black, a transparent pigment (if I were to do it again, I'd use
>> >>> lamp
>> >>> black) and (b) the fact that it's printed on a transparent
>> >>> material and was scanned as a transparency, with the light
>> >>> shining
>>through it.
>> >>> But the thing to note is, be that as it may, the DMax is about
>> >>> the same in both prints.
>> >>>
>> >>> (2) there's a light brown pigment stain (ivory black is a
>> >>> brownish
>> >>> black) in both prints that is probably a function of the heavy
>> >>> pigmentation. It hardly shows in the prints themselves, but for
>> >>> some reason was accentuated in the scanning.
>> >>>
>> >>> (3) I don't honestly know what to make of the results. If you
>> >>> look just at the prints on mylar, you'd have to conclude that
>> >>> back- printing is much superior to front-printing, at least for a
>> >>> thick coat on mylar. But if you compare the back-printed print on
>> >>> mylar to the regular front-printed gum print (using a less
>> >>> heavily-pigmented emulsion) on paper (at the bottom of the page),
>> >>> it's hard to claim that the back-printed print is superior. But
>> >>> since they are on different materials, it's apples and oranges.
>> >>>
>> >>> So I guess if I were forced to draw a conclusion from this rather
>> >>> inconclusive test, I'd say that if you are going to print on
>> >>> mylar using a very thick and heavily pigmented emulsion, then
>> >>> you'll probably do better printing from the back. But if you're
>> >>> printing on paper, you can get fine results printing from the
>> >>> front with a less pigmented emulsion.
>> >>>
>> >>> http://www.pacifier.com/~kthayer/html/topdown.html
>> >>>
>> >>> Katharine
>> >>>
>> >>>
>> >>
>> >>
>> >>
>>
>>
>>
>>
>>
>>
>>
Received on Tue Apr 11 13:39:56 2006