Re: APIS, hydroquinone hardening

Katharine Thayer wrote:
>
> I agree with Ryuji here; I guess I don't get what the point would be to
> doing it this way rather than just using one of the common hardeners for
> the gelatin.

And besides, I'm a bit skeptical about a rubberlike surface working well
for gum; I've tried printing on surfaces that have a rubbery quality
(like paper coated with waterproof ink) and found that gum doesn't
adhere well to such surfaces. But will be happy to be pleasantly
surprised by data, as always.
Katharine

>
> Ryuji Suzuki wrote:
> >
> > 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.
> >
> > 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 16:09:57 2005