RE: gloy for tricolor on yupo?

Hi Katherine,

-----Original Message-----
From: Katharine Thayer [mailto:kthayer@pacifier.com]
Sent: 31 Mart 2006 Cuma 03:42
To: alt-photo-process-l@sask.usask.ca
Subject: Re: gloy for tricolor on yupo?

> "... Like I said, a slight brain malfunction. sorry..."<

No problem since you clarified the issue...

> "But I must take some mild issue with your statement "I expose ala
Christina, at least 6 minutes-- making relatively sturdy layers." The
exposure time required to make "relatively sturdy layers" is a
function of so many things (light source, negative, type of
dichromate and concentration thereof, and relative humidity, for
starters) that it is simply meaningless to state an absolute exposure
time that will result in "relatively sturdy layers." <

That statement wasn't about a specific exposure time at all. It was
about "making sturdy layers". Each have to work his/her own parameters
in achieving this... AFAIK, we use the similar lightsource, similar
negative substrate but different gum (obviously) and dichromate ratios
w/Christina (I use 5% dichromate - since my lightsource is twice as
strong as hers, it makes sense that my exposure time is close to hers
even I use a lower dichro concentration).

> "...But I use saturated ammonium dichromate and I live in a very
humid climate, which together probably account for most of the fact
that I can print a very sturdy layer in a short time. If I were
using potassium dichromate, or diluted ammonium dichromate, or if I
were living in a drier climate, exposure times to make a sturdy layer
would be longer (and in fact my times are longer during rare dry
spells here."<

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

>"Loris, I didn't ask if you thought it should work, I asked if you
knew anyone who had done it. But I think maybe a couple of things are
being confused here. As to coating, I can coat yupo with gum easily;
the issue for me with gum and yupo isn't the adhesion of the coating
to the yupo but the adhesion of the hardened gum to the yupo, which
is a completely different issue."<

But what makes you think: the PVA which adheres perfectly to the
substrate before exposure should (or may) loose that property when
hardened? We know that colloids hardened in different ways such as
gelatine + formaldeyhde / glutaraldeyhde / alum... (silver gelatine) /
dichromate (carbon + oil) , egg + dichromate (temperaprint), gum +
dichromate (gum dichromate)... somehow manage to stay on the substrate
they were applied. Is there any example denying this fact?

Regards,
Loris.
Received on Fri Mar 31 01:38:51 2006