U of S | Mailing List Archive | alt-photo-process-l | Re: oil printing

Re: oil printing

Sorry, I forgot to answer the other part of your question, why in oil printing a negative is used, and in gumoil, a positive, when it seems like they should work sort of the same way. You're right that in both cases the oil paint is deposited mainly in the shadows and less in the midtones and highlights, so it seems like you'd need the same kind of intervening matrix. The difference is in the qualities of gelatin vs the qualities of gum, which makes them behave differently when acting as a resist for the oil paint. For gumoil, you use a positive to expose the gum backwards (more hardened gum in the highlights, not much or no hardened gum in the shadows) and then you wash off the unexposed gum, leaving the hardened gum to serve as a resist in the highlights and partially in the midtones and the paper free to accept the oil paint in the shadows. For oil printing, you expose a negative to harden the gelatin most in the shadows; when you put it in water to wash out the dichromate and to swell the gelatin in the highlight areas. Then the oil paint is applied; it sticks to the hardened gelatin in the shadows and is repelled from the swollen gelatin in the highlights. Same result, but opposite ways of getting there. Does that make sense?

Hope that's helpful, and Henk, I hope you'll set me straight if I've got this wrong somehow. I've done one gumoil in my life, just to see what it was like, and no oil prints, but this is how I understand the principles involved, and since no one else seemed to be answering the question, thought I'd just blunder in.

On Sep 26, 2008, at 7:21 PM, Katharine Thayer wrote:

Sorry to barge in here, but I'm having trouble following this conversation. Dirk asked a question about why there's no hardener in the gelatin layer, and since the subject line is "oil printing" I assumed he was asking about the gelatin layer in oil printing. But the answer that came back seemed to be about the gelatin layer that acts as a size for gum printing, which I, for one, found quite confusing.

On the chance that I had it right in the first place and the question was about oil printing, the answer is that there's no hardener in the gelatin because in oil printing you don't want the gelatin to be hardened as a whole layer, as you would if you were using the gelatin as a size for gum printing. You only want the gelatin hardened where it's exposed; that's the purpose of the dichromate. Just like you wouldn't put a hardener in the gum that you're using for a gum print, because you don't want *all* of the gum hardened, just the gum that's exposed. Hope that's the question you were wondering about..

If I was wrong and the question really was about sizing for gum printing, then I might suggest that it can be helpful to change the subject line if the subject changes, so people trying to follow the thread can make sense of it. Thanks,

Oh, and by the way, while we're confusing the two issues: part of the answer about sizing for gum printing seemed to suggest that if the glyoxal were mixed into the gelatin before being applied, rinsing might not remedy the yellowing problem. In my experience, that's not a worry. I apply the gelatin with the glyoxal mixed in, and rinsing does remove the yellow, in fact I don't bother to rinse separately after sizing, because though the sized paper does turn yellow in a few days, it returns to pure sparkling white in the development phase of gum printing. So I don't find any need for a separate rinse. There, now I've given you an answer for either possible meaning of your question. :--)

By the way, I enjoyed seeing your prints, and noticed that you took a workshop from Kees. Look forward to seeing your progress,

On Sep 24, 2008, at 11:52 PM, Dirk-Jan Treffers wrote:


Just a wondering thought: Is it on purpose that you omit the use of hardener in your gelatine layer? I also found more or less the same recipe on alternativephotogrphy.com, and there also the use of a hardening agent like glyoxal wasn't mentioned.
Is that correct, and if so, what's the reason for that?

And another question (you see, I'm curious)... why is that in oilprinting, a negative is used, while in the gumoil process (which sounds more or less the same...) you need a positive....

thanks already!


2008/9/25 Judy Seigel <jseigel@panix.com>

On Wed, 24 Sep 2008, henk thijs wrote:
OILPRINTING is a contact-procedee like gum, cyano etc..
Coating a 300grams paper -like you use for gum- with a 10% gelatine, three times, let dry and coat with a 6% potassium dichromate.
Like gum, put the neg on top , UV-light for twice the time you expose gum.
Wash out the chromate, gelatine is partly harded and now you have your matrix for oiling.
Info about the ins and outs are difficult to find; in David's book, the chapter about oilprinting is a bit thin. I had to do a lot of testing (or better: paperbasket filling with rubbish) before making oilprints ; but if you succeed there is no need for a darkroom anymore (and if you have anyway a suitable negative and some chromate ....).

The books and magazines of Demachy's period when oil printing hove into view have many articles about that process, some, I daresay quite complete.

I found them appealing, but resisted for a number of reasons, including and especially because I'm allergic to the solvents (and warn anyone using oil paints be careful: Turpentine is one of the two most allergenic substances for humans. The other is chrome, tho I don't know if that extends to all forms, including dichromates, or just shiny bumpers.)

In any event don't get your hands in the turp, or yr feet either for that matter... I now use odorless mineral spirits when the need arises -- tho some labelled "odorless" lie -- so far OK, but I'm careful, ie, don't leave the stuff in an open container, and if I have it on rags or whatever, dispose of them in a closed container in another room... etc.) The worst, probably, is in a classroom -- imagine 30 palettes or trays in an enclosed space wet with turpentine !!!! (Yeah, in the good old days.)

Meanwhile, I'll check some of those period annuals, or whatever I find in the Mississippi delta AKA my book shelves. Or aren't there indexes of that literature somewhere?

PS to Henk: Sorry I can't join in the chorus of praise, because I have to switch partitions before I can see those prints... gotta get myself into giraffe, or whatever it is...

But soon, I hope....