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Jan Van Hove
18-Dec-2004, 01:13
Hi,

I researching papers for alternative processes as well as alternative processes themselves, i've come across a tidbit of information that i've found intiguing : Watercolor papers are gelatin seized...

Why did I find it interesting ? I'm in the process of trying to make oilprints, the process of which is very simple : you coat a piece of paper with gelatin, you sensitize it with potassium bichromate, and expose to daylight. The bichromate hardens the gelatin in areas of the negative that are lighter, and then you put a coat of oil ink or paint over all of that and you get an image... (it's not that simple, but it's the general idea of the process...)

Now, some people suggest using regular photographic paper that has been fixed to eliminate silver salts, leaving a hardened gelatin surface that can be bichromate-sensitized. If all you need is gelatin, could one use gelatin seized watercolor paper with some succes in making oilprints ?

I know that the Arches platinum paper is the recomended paper for alternative processes involving metallic salts and chemical developments, but since oilprints depend solely on gelatin hardening, and that the colors are provided by oils, the no-chemical-additives-to-the-paper rule is probably less severe for this process...

Any insight would be welcome, and i'll tell you how it goes with my current experiments...

Cheers,

PJ

CP Goerz
18-Dec-2004, 01:45
I think theArches paper you mention is possibly too thin for the type of wear the paper will take from your work on the surface. Watercolour paper is a bit tougher and made for reworking so maybe that is the way to go, just my 2Cents!!

Photographic paper thats fixed out may have the gelatine hardened too much to have any effect from the dichromate though that wouldn't stop it from being stained, possibly some experimentation is needed. At one time Kentmere made an unhardened paper but I'm not sure if they do anymore.

CP Goerz.

Jan Van Hove
18-Dec-2004, 01:53
Hi andrew,

The photographic paper option was not on my list of tryouts anyway, but what I wanted to know is if the Gelatin content of watercolor paper is enough to react to bichromate and allow for the differential hardening and subsequent water swelling that allows to create oilprints...

Thanks for the insight !

PJ

Robert Musgjerd
18-Dec-2004, 04:34
Try Bergger cot 320 quite strong great wet strength acid free satiney smooth white surface.I use it for platinum
& palladium printing . Bostick & Sullivan sell it along with other papers for alt printing

Happy printing

Jan Van Hove
18-Dec-2004, 05:07
Ok,

I don't think I'm asking the right question...

I know the importance of gelatin seized papers to limit the absorption of sensitizing materials in the paper, but the oilprint process depends on differential hardenig of the gelatin to create an image...

I just want to know if Watercolor papers with respond to Bichromate-induced hardening.

Maybe I'm asking something that no one has tried, and if it's the case I'll be happy to oblige as soon as i get my hands on watercolor paper...

Cheers,

PJ

Brian Ellis
18-Dec-2004, 05:26
A better source of information about alternative processes than this group is the alt.photo.process group. Google and it should pop up. Everyone there does some sort of alt process and you'll almost certainly find someone who has tried oil without sizing. Unless the group has changed you'll also find some major egos, petty arguments, and childish behavior but if you can get past that stuff it's an excellent group for alt process information.

FWIW, and it probably isn't worth much, with gum printing only one or two papers could be used without a separate sizing step. I actually didn't remember that all watercolor papers were sized in the manufacturing process and I'm not sure you're correct about that though you may be, it's been several years since I was involved with alt processes. But if it is then apparently the sizing isn't real effective for most alt processes except in the case of those one or two papers (the names of which I have of course forgotten).

Pete Watkins
18-Dec-2004, 05:36
I don't know if it is possible to "oversize" a paper but it might be worth sizing the paper that you intend to use yourself. With a bit of luck this might guarantee some sucess. Not all watercolour papers are sized as far as I know.

Pete.

Jorge Gasteazoro
18-Dec-2004, 05:45
No, it would not. You need to add gelatin dissolved at greater concentrations than the one used for sizing. Arches Platine has very litle sizing of small cocentration gelatin and for the kind of process you want to use you require a solution with enough concentration so that you can coat the paper. You can certainly coat Platine, but no use it by itself without an extra coat.

You definitly can use Platine, it's wet strenght is just as good as COT320 if not better, and the pressed surface is smoother than COT320. If you are not willing to size paper, then the best solution is to use fixed out paper hardened in bichromate.

BTW not all papers are sized with gelatin, some are sized with arrowroot, which might not be useful to you.

Jan Van Hove
18-Dec-2004, 06:09
Ok, Thanks for the info !

for now i'm experimenting with gelatin coated paper, and i still have to master the oil part of the process, i tend to just rip out the gelatin from the surface of the paper... It'll take a few attempts before i get this right...

PJ

Wayne Firth
18-Dec-2004, 11:22
Patrick,

This article might be helpful to you:


http://alt-photo.com/alt-photo/bromoil/ARTICLES/oil%20prints%20ern.html (http://alt-photo.com/alt-photo/bromoil/ARTICLES/oil%20prints%20ern.html)

One coat of gelatin will not be enough. Be thinking of something like six coats with total immersion in a tray. Coating both sides will reduce the curl.