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 11:49:34 2006