Re: APIS, hydroquinone hardening

Thanks, Jack, for the more complete explanation. I was too busy with my
brain wheels turning about a possible gum size to take complete notes on his
processes.

The reason for the interest to those not present at APIS: at the moment, we
have glut, gly and formaldehyde for hardening a gelatin size. All have
questionable toxicity for some people. I personally love glutaraldehyde if
I can ever spell it correctly, and use that in my practice, and I agree with
Ryuji's comments, below. Clay H. has given up glyoxal and gone to chrome
alum. Sandy King uses chrome alum. Katharine, Sam, and others don't size.

Paul's system (having NOTHING to do with a possible size, but part of his
carbon-q process if I remember correctly) is having a 1%-3% amount of
dichromate in the gelatin already, and the hydroquinone amount is so small
(if I remember, 0.5%) that my idea would be to size the paper in a tray of
the di/gelatin, and then pass it thru a bath of the hydroquinone (Paul had
added a pinch of hydroquinone to the gelatin/di mix and voila, instant hard,
which is why I thought to try the bath of hydroquinone). The miniscule
amount of dichromate left after the baths should not be a problem but heck,
until I test it out who knows if it does or doesn't work. I hope others
will try it. Maybe it is a bust. BUT, presuming in a class of students
where you are already teaching gum printing with dichromate, the use of di
and a pinch of hydroquinone would seem to be less toxic than other
choices...perhaps.

As always, theorizing is one thing, trying it out is another. I plan on
trying it out and hope others will, too. I'm not sure how I will try it,
how I will combine it, but I will stick to the proportions that Paul shared
because at this point that is all I have to go on. Like testing to see if
boiled gelatin ruins a size, all you gotta do is boil some gelatin and find
out (which I did, and it doesn't).
Chris
> From: Jack Brubaker <jack@jackbrubaker.com>
> Subject: Re: APIS, hydroquinone hardening
> Date: Wed, 13 Jul 2005 14:58:35 -0500
>
> > As a fellow gum printer who doesn't feel I have found the Holy Grail of
> > sizing options I to was excited about this idea. Paul found that a
gelatin
> > coating that contained a small amount of hydroquinone could be hardened
by
> > the addition of a small amount of dichromate.
>
> Ryuji says: This can work, but the net effect should be similar to
addition of
> chrome alum. Presence of oxidized hydroquinone in absence of sulfite
> may also help to form a different kind of crosslinking. But personally
> I don't see why one might want to use more than one step of work for
> the hardening process when one is enough. Addition of a very small
> amount of glutaraldehyde immediately before coating works as good as
> anything else I tried and it is by far the easiest hardening process I
> know of.
>
> > The dichromate could be either brushed on and then washed off once
> > the reaction had occurred or perhaps the usual gum coating could be
> > brushed on and the sizing under it would be "set" by the dichromate
> > in that first layer of gum.
>
> If you do the latter, I would expect the "fog" level to rise.
>
Received on Wed Jul 13 17:23:42 2005