RE: gloy for tricolor on yupo?

Hi again Katherine,

-----Original Message-----
From: Katharine Thayer [mailto:kthayer@pacifier.com]
Sent: 31 Mart 2006 Cuma 18:21
To: alt-photo-process-l@sask.usask.ca
Subject: Re: gloy for tricolor on yupo?

L> Type of dichromate should be completely out of equation given the
L> molecule count per volume of coating solution remains the same.

>"...That's what I thought, until I read this study, which started from

the observation: " It has been established for a long time that
holograms formed from ammonium dichromate as a doping chemical were
of better quality than those obtained with potassium dichromate. So
far, no satisfactory explanation has been given to this experimental
observation. Thus the aim of the work [in part] was to determine...
the specific role played by ammonium cations: why does ADC doped PVA
yield better holograms than KDC doped PVA?" They calculated the
weight of the two dichromates to "obtain the desired chromium
percentage in weight respectively which corresponds to the same
ratio, Cr(VI)/PA unit" for each of the dichromates, and found that
even at the same "molecule count per volume" as you say, the ammonium
dichromate created a more stable image; they concluded that the
"improvement brought by ammonium dichromate with respect to potassium
dichromate involves amide groups as additional chelating sites for
chromium (V) resulting in the increase of the matrix crosslinking."

Bolte etc al "Hologram Formation Reconsidered in Dichromated PVA:
polymer crosslinking around chromium (V)." in Practical Holography:
Materials and Applications, SPIE proceedings 2005..."<

L:
Wow, thanks for passing that information. What's the binder in
holography? Does that strictly apply to gum or dichromated PVA? What is
the meaning of "creating a more stable image"? What is your experience
with both of them? Does it show in the print which dichromate you had
used?

Sorry for asking that much questions :)

L> But what makes you think: the PVA which adheres perfectly to the
L> substrate before exposure should (or may) loose that property when
L>hardened?

K>"Well, goodness, I don't just "think" that;, I know it from much
experience coating glass and yupo and mylar with nice smooth even
coats of gum that "adhere" to the substrate beautifully but then in
development the hardened gum floats off into the water. This
knowledge that the adherence of the coating and the adherence of the
hardened gum are two different issues is a product of experience, not
just a speculation."<

Have you put the coated paper in water before exposing to see if it
sticks better than when unexposed?

Yes, I know it's an incredibely silly question. I'm just trying to
explain my point in the original question - you simply can't draw a
conclusion such as "adhesion of hardened PVA is less than unhardened
PVA" by developing prints in water. You have to test without using water
to say something like that. It's perfectly fine to say "x type of PVA
doesn't adhere to Yupo after exposure, when developing", that will show
us it's not a fine binder for using on Yupo - that's all, it won't tell
us about the before and after exposure adhesion properties.

My point is: I see a better chance in Gloy / PVA for making multi-color
(or multi-layer) pigmented dichromated colloid images on Yupo when
compared to gum arabic. Because it's more flexible and has better
adhesion properties than than gum ("I think" for the latter). Gum
probably is not a good benchmark for Gloy, I'd choose whole eggs as a
benchmark.

BTW, the URL which David pointed out is very fine. Will read that in
detail + will also re-read the PVA related messages on the list and go
out to hunt for a good PVA to start with in order to make tests. If I
manage to find something that works that will be wonderful.

Thanks for passing/sharing info.
Regards,
Loris.
Received on Fri Mar 31 11:01:36 2006