Re: (Gum) Tonal scale

Okay, I've spent some time this morning trying to show you how for me,
a crosslinked matrix of unpigmented gum is clear and colorless, not
just on mylar but also on paper (here, Arches bright white).

First, I printed two step tablets side by side, which I show you here.

http://www.pacifier.com/~kthayer/html/gumnocolor.html

All you see is a white field. If I still had my old version of GoLive,
I could have given the page a different-colored background so you could
at least see the paper against the background, but I don't see where to
do that in the new version; it's not where it used to be. As it is, the
white of the paper is close enough to the white of the background that
it doesn't distinguish on the page.

Then I tried to figure a way to make the gum image (this is why I'm not
sure I can agree to reserve the term "gum image" for a gum image with
pigment in it) visible so you could be convinced it was actually there.
  I thought of doing a dusting-on process, but I don't have any dry
pigment, so I tried powdered graphite, and what a mess. I'm obviously
not quite up on how to do the dustin-on thing. Anyway I ended up with
black powder all over the studio; I ruined my little puff bottle that I
use to puff a little powder onto the back of FP4 to keep it from making
Newton's rings against the glass when I print with FP4; I put the
graphite into it in a vain attempt to get finer clumps of graphite,
and now I will have to buy a new one to powder FP4 with, and after all
that, all I had was a big mess. So I'm giving this up as a lost cause;
I'm cross and I'm done with this for now. You'll just have to take my
word for it, I guess.
Katharine

On Dec 6, 2005, at 11:18 PM, Katharine Thayer wrote:

> Man, this is like playing darts blindfolded, or something of the sort.
> Everyone is replying to a different set of posts, in a different
> order. It's pretty crazy......
>
> I didn't see Yves' post that Mark is responding to here, and have a
> couple comments to it.:
>
> If you "print" with plain dichromate, the dichromate will react with
> the factory sizing in the paper, even if you don't add extra sizing,
> and will form a crossliked matrix, even an image if you use a negative
> with it. (I uploaded some examples of this some months ago and may
> still have them around somewhere). If you're a person who gets
> dichromate stain in your practice, this matrix will be stained so you
> can see it; if you're not, the matrix will be invisible, unless you
> hold it at an angle to the light, and then you'll be able to see it in
> relief. (These things are also true of unpigmented dichromated gum.
> Why some people get dichromate stain and others don't has occupied
> many weeks of discussion on this list and hasn't been resolved, but I
> don't think it makes any difference practically to the crosslinking
> process.
>
> What I showed on mylar I also get on paper, with unpigmented gum. If
> I print an image in unpigmented gum on paper, I get exactly the kind
> of effect I keep telling you about, where you can't see the image
> until you turn it to the light and then you see it in relief. ( It's
> really a pretty cool effect. I've always wanted to do something with
> it for an exhibition print, but haven't got around to it yet. ) If I
> have time tomorrow, I'll show you. The problem is that I can't show
> the invisible matrix because the scanner won't see it; I would need to
> take it at an angle, and I don't own a digital camera to do that. But
> maybe I can figure out a way.
>
> Katharine
>
> On Dec 6, 2005, at 6:41 PM, Ender100@aol.com wrote:
>
>> Try Dichro on paper by itself and expose it with a standard test
>> tablet and see how it comes out...
>>
>> In a message dated 12/6/05 9:25:55 PM, gauvreau-yves@sympatico.ca
>> writes:
>>
>>
>>
>>
>> Mark,
>>
>>  
>>
>> your are right about missing posts, something funny is happening
>> with the server(s) I suppose.
>>
>>  
>>
>> At first I thought that in Joe experiments the stain could be caused
>> by the dichromate "reacting" with the gelatine used in sizing but I
>> tried the same test without sizing the paper. I though that whatever
>> color I would see immediatly after the exposure would dissapear in
>> the water but surprise, this dam dichro stain had a mind of its own
>> and just stayed there on the paper. Now, I'm thinking there must be
>> something in the paper that "reacts" with the dichro??? When I
>> received Katharine message and went to see her own experiment made
>> with gum and dichro I kind of said to myself what if there was only
>> dichro on mylar or some other material that would most likely not
>> "react" with the dichro??? So I tried a bit of dichro on glass and
>> guess what??? If you think the dichro stayed on the glass, well it
>> didn't. I also tried a couple more things like putting some dichro on
>> paper, let it dry after and try to wash it off, yes it worked fine
>> and as far as I can see I got a clean paper back. I even tried to
>> force out the stains out of previously exposed dichro+paper using
>> only water but contrary to unexposed dichro+paper I was left with
>> what I call a 'ghost image' showing clearly the exposed area but
>> without significant color, something like Katharine blue grey but
>> definitively not paper white.
>>
>>  
>>
>> Why does it stay on some material and not on others??? I don't know
>> for sure, I don't know either if it's a chemical or a physical
>> "reaction" though I'm 100% sure there is a portion of what happen
>> that is physical. I suspect the UV light causes a physical change in
>> the structure of the dichromate, the details of which I'll leave to
>> more knowledgable people. These changes must do at least 2 things at
>> the same time if not more. One of these can be associated with the
>> staining effect and the other can be associated with the conversion
>> of soluble gum into clear insoluble gum. By the way, this
>> 'insolubilisation'  can happen with many different materials.
>>
>>  
>>
>> From the experiment I did I would suspect some part of the
>> dichromate (colored) byproduct after exposure must have some mean to
>> stick on porous materials but it seems this stuff remain soluble in
>> hot water and washes off relatively fast and the other near clear
>> part either become insoluble and leave this 'ghost image' I saw or it
>> as a stronger link with the paper that water alone can not break.
>>
>>  
>>
>> Regards
>>
>> Yves
>>
>>
>>
>>
>
Received on Wed Dec 7 13:44:50 2005