Re: Tooth and consequences: Yupo

Hi Katharine,
Too complicate for me, too many things involve (tooth, yupo, CYMK)
I am also moving to a different location.
I will be off for a while,
Giovanni

----- Original Message -----
Wrom: NNYCGPKYLEJGDGVCJVTLBXFGGMEPYOQKEDOTWFAOB
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, November 14, 2004 8:31 AM
Subject: Tooth and consequences: Yupo

> Hi All,
> I unplugged myself from the list yesterday so I could get back to a
> project that I've been neglecting; I apologize for dropping out of on
> ongoing debate but will try to catch up later if there's anything I need
> to respond to; anyway I've pretty much already said what I know from
> experience about tooth.
>
> In the meantime, I had ordered some paper from Daniel Smith and because
> they have a minimum order of 10 sheets of loose paper and there weren't
> 10 sheets of paper I needed to order by the sheet, I ordered a piece of
> Yupo just for the heck of it, because I've always wondered what it was
> like, and because it was cheap. So when I was unpacking the paper order
> into my flat file, it occurred to me that this Yupo would be a good
> thing to check my understanding about tooth. And besides, I wanted to
> check, one more time, my answer to Giovanni about gum not hanging onto
> gelatin.. My experience has always been that if you've got a surface
> that's too slick to start with, sizing that surface isn't going to help;
> the gum won't stick to the gelatin much better if all than it would
> stick to the slick surface in the first place. But since Galina prints
> gum on glass by sizing with gelatin, that certainly isn't a universal
> rule, and so I was curious what would happen if I sized a piece of
> Yupo. I found that sizing the Yupo did not improve its ability to hang
> onto the gum, which frizzled and flaked off the surface. When I sanded
> the unsized Yupo to give it some tooth, the gum adhered to the surface
> well. I used 320 grit sandpaper, which scratched the surface too much;
> the scratches were visible in the final print, especially when viewed at
> an angle. The only finer sandpaper I had was 600, and I found that that
> didn't scuff the surface enough to make the gum adhere.
>
> The main message I want to convey here, believe it or not, is that I
> found the Yupo a very interesting material to work with. It doesn't
> behave anything like paper; for example I found that exposure times
> didn't correlate well with my previous exposures with paper, and the gum
> coats on the Yupo very differently than it coats on paper, or even on
> mylar. But I also think that if a person were to spend some time with
> this stuff, one could learn to use it with gum and get some very
> interesting results. And it's very cheap, $1.88 per 20x26 sheet.
>
> Then I had a brainstorm: I thought hey, this might be a quick way to get
> Joe's RGB-CMY comparison that he was so determined that I should do for
> him: if I used an image that would print well at a small size (the
> callas I made separations for before are too subtle in tonal gradation
> to print well either small or probably on a hard surface either, so I
> used a different image) and printed both types on the same piece of
> Yupo, I should be able to finish the six separations in a very short
> time; since I know from experience that gum on a nonporous surface dries
> very fast, I should be able to do the whole thing in less than an hour.
> So I did this, but the result was not very successful. Even sanded, the
> Yupo can retain at best two color layers, it seems, so neither the RGB
> nor the CMY print kept the cyan layer except in selected spots, mostly
> where the yellow and/or magenta negatives masked that area so the cyan
> was the first layer or second layer to actually print on that spot.
>
> And of course the other thing is that the two sets of separations are so
> different that it doesn't make sense to do them with the same exposure
> and development. So if I were to do this comparison seriously, I would
> need to make two separate prints, an RGB print and a CMY print. From
> what you can see of the flawed prints, the RGB looks better than the
> CMY, but that's because of course the CMY separations are less dense and
> so need either less exposure or more development or both to turn out; it
> doesn't work to do them on the same sheet as the RGB.. So, as I say, I
> wouldn't take ANYTHING from this failed comparison, except to note how
> the gum prints on the sanded Yupo.
>
> At any rate, as I've said before, the question of whether RGB or CMYK is
> better isn't very interesting to me. The way I look at the RGB-CMYK
> thing, if you're used to RGB separations and know how to use them, then
> you will get good results from RGB separations, and if you're used to
> CMYK separations and know how to use them, you will get good results
> from those. As I've said before, I don't think there's a right or wrong
> on this, and I think it would be very difficult to establish some kind
> of accurate judgment of whether RGB is inherently more accurate than
> CMYK or vice versa, since so many other things go into the final color
> balance: pigment choice and how the pigments behave in combination with
> each other, skill in printing, probably even the gum used, etc etc etc.
> So I don't think this is an issue that can be resolved, and since I
> don't have time or energy for the things I really need to do, I don't
> put a real high priority on adding more data one way or another to this
> issue.
>
> Here's the URL for my experiments with Yupo:
>
> http://www.pacifier.com/~kthayer/html/Tooth.html
>
> Since I wasn't setting out to do a test or demonstration to prove
> anything to anyone, I used different negatives and pigments, whatever I
> needed to use up a bit of at the time. My goal isn't to set out a rule
> for all the gum worlds, but just to show how things work in mine, as
> always.
> Katharine Thayer
>
> gdimase@hotmail.com wrote:
> >
> > Hi Katharine,
> > Then, how do you theoretically explain when you print gum on top of
glasss
> > or alluminum?
> > If you don't size it you can't get the image on the gum.
> > Glass and alluminum are perfectly clean without any "tooth" and you can
> > print perfectly on them, right?
> > Giovanni
> >
> > ----- Original Message -----
> > Wrom: NNYCGPKYLEJGDGVCJVTLBXFGGMEPYOQKEDOTWFAOB
> > To: <alt-photo-process-l@sask.usask.ca>
> > Sent: Friday, November 12, 2004 6:54 AM
> > Subject: Re: Help with what I believe is a hardening issue
> >
> > > gdimase@hotmail.com wrote:
> > > >
> > > > I have being reading this thread and seems to me that there is a
major
> > > > confusion.
> > > > The purpose of hardening is to the gel not to the paper.
> > > > The gel is going to carry the pigment colors meaning the image,
> > obviously
> > > > the gel is on top of the paper but it can be on top of anything.
> > > > Does anyone disagree with me?
> > >
> > >
> > > Hi Giovanni,
> > > In my gum universe (which appears in many respects to be a parallel
> > > universe to some other gum universes, but that's what makes the study
of
> > > gum so endlessly fascinating) the gel is on top of the paper, as you
> > > say, but the gel isn't what the gum is hanging onto. If you looked at
a
> > > cross section of paper through a microscope, you would see fibers
> > > sticking up off the surface of the paper. It is those fibers, which we
> > > call "tooth," that the gum grabs onto and that keep it from floating
off
> > > the surface. If sizing is so thick or heavy that it clogs up the
tooth,
> > > then the gum coat will flake off the paper because there's nothing for
> > > it to hang onto. Gum doesn't "stick" to sizing; it sticks to whatever
> > > tooth it's got to hang onto in the substrate. My 2cents, and as I say,
> > > this applies only to the gum universe I know,
> > > Katharine
> > >
>
Received on Mon Nov 15 15:35:18 2004