Re: APIS, hydroquinone hardening

From: Jack Brubaker ^lt;[email protected]>
Date: 07/13/05-01:58:35 PM Z
Message-id: <BEFADC9A.1224C%jack@jackbrubaker.com>

Christina mentioned in reference to Paul Lehman...

>he discovered that
> (Katharine Thayer, this might interest you!!) gelatin with a touch of
> dichromate and then a pinch of hydroquinone instantly hardens into a rubbery
> mess. He talked about crosslinking of gelatin and gum, and the light bulb
> went off in my head about a new possible way of sizing with less toxic
> stuff.

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. The two ingredients can't be
mixed together in the gelatin because the reaction between them will go off
almost instantly. He commented he has two beakers of "rubber" created by
mixing hydroquinone and dichromate in gelatin. Within 30 seconds he said the
solution went from liquid to solid, trapping the stirring tool he was using.

He has made prints by a very clever "wet carbon" process where he uses this
reaction to selectively solidify carbon tissue (that contains hydroquinone)
still damp from coating by placing it in contact with a paper final paper
support that has an exposed dichromate image (dichromate only). The
unexposed and therefore unconverted dichromate bleeds into the carbon tissue
and interacts with the hydroquinone to harden the gelatin. The image bonds
onto the dichromated support and is developed as in traditional carbon
transfer. The forgoing is a very brief and I hope not misleading account of
the process as I recall it. He had prints he had made by this process that
showed promise. He had so much to say and covered it so quickly that I
couldn't make meaningful notes so the above is from memory. I hope Paul will
write up a more complete and accurate account for us all... He had "slides"
in his PowerPoint that detailed the formulas he has used, but I was so
engrossed in being sure I understood him that at the rate he moved through
his information I didn't get it all written down. Sullivan mentioned he
hoped to post all the presenters visuals on his site in the near future.

But to return to my topic, using this hardening effect as a gum size. I
don't have the materials yet but plan on trying applying a gelatin and
hydroquinone size that would be hardened by subsequent application of a
dichromate. 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. The appeal to me is that the reaction is very quick, it
is powerful, and the hydroquinone is non-threatening for skin contact (an
active ingredient in age spot removers). Paul said that although one
wouldn't want to ingest the stuff it is quite safe. A far cry from most of
the hardeners now in use.

Jack
Received on Wed Jul 13 13:57:57 2005

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