Oh yeah, one more thing on the ferric ammonium citrate thing Saidane is doing: his development temperature is ridiculously low. He mentions 30-32C. Normal carbon transfer development temperature is 40-42C! AFAIK gelatin won't even melt at 30C, so I wonder if it's a typo or of this is part of the secret sauce.
The other thing is the use of oxalic acid to bring the pH down to about 3-4. Do you and others also do that?
Ah, that's interesting. I also received a screen printing kit which I mostly bought because of the azo sensitizer that came in a separate bottle. It's kind of expensive for how little of the sensitizer you get, but for an experiment it's OK.
I emailed a bit with Kees Brandenburg and he mentioned the screen printing azo sensitizer basically sucks. It leaves a stain that can't be cleared, in contrast to DAS. It's not very high at the top of my list trying it. Let's hope I get there before the stuff expires.
I did notice that the actual emulsion is indeed a PVOH/PVAc mixture. Given this I'm not surprised it doesn't melt nicely since PVAc isn't water-soluble to begin with. Let me know how it goes with the PVOH!
Hi, I don’t know if it’s very useful but I’ve been doing the ammonium ferric citrate thing with both gelatine and casein and have had reasonable results. The bobbins use casein, the flowers are gelatine based and the cloisters are gelatine and graphite.
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I would say they are more than reasonable
the ammonium ferric citrate thing
I would say they are more than reasonable - they are rather lovely, particularly like the Flowers. Is the Cloisters one layer or multilayer? Can you tell us about the negatives?
Thanks for sharing.
:Niranjan.
Certainly so! They're intriguing. I really like the one of the bobbins due to its relative color accuracy. It suggests the approach is capable of quite good results.
Kees Brandenburg also does casein prints (and workshops on them). I don't know if he also uses FAC as a sensitizer or if he relies on DAS.
Concerning stain which you mentioned elsewhere: I noticed a greenish brown sensitizer stain with FAC. How do you clear it?
Also I’ve learned that some watercolours just stain like crazy and are just to be avoided.
Have you tried Ferric Carbon double transfer Koraks?
I've heard varying reports of how well Double Transfer works with Ferric Carbon though.
In Sandy's (and others) Carbon Printing book I believe it mentions that Ferric Carbon on an albumen substrate should work
From what I've gathered the most successful way to do Ferric Carbon is using fixed out silver halide film like Lith Film and the image is simply put on top of a piece of paper to display it (glued somehow?)
Yeah, pigment staining is an issue with processes that go directly onto paper. It also somehow turns out that pigments that are otherwise ideal (e.g. in terms of transparency and longevity) stain the worst. Pb15:3 and Pr122 come to mind - they're great, but stain very strongly. Pbk7 too.
What I'm interested in however is sensitizer staining in particular. Here are two experiments I did a few days ago with ferric carbon:
The first one is a Pb15:3 carbon tissue I had lying around that I brush-sensitized with a ferric ammonium citrate + ferric ammonium oxalate sensitizer.
The second is a Pbk7 tissue with a FAO + FAC sensitizer incorporated into it. It's the most successful test so far, but this too has some adhesion problems.
In both instances a very heavy sensitizer stain is visible. This is both onto gelatin-sized paper. Sizing is ca. 25g dry gelatin per square meter, hardened with chrome alum. It's easy to see the edges of the paper where the carbon tissue didn't touch it and the yellow-brown center part where the sensitizer stained the gelatin sizing. I haven't tried clearing this yet, and I was curious if anyone already has - and has experienced the issue, to begin with. The stain isn't quite as bad as with DAS, but it's very much more pronounced than dichromate staining.
Let's see if I understand this correctly: somehow iron that is being washed out fro the tissu is getting back on the paper and judging from the color, being hydrolyzed to Fe(OH)3.
Are the stains also on the back side of the paper?
Is the paper alkaline, or the tap water?
Yes, that's what I'd make of this as well.
The process by which the stuff gets into the paper is also kind of evident. During the transfer, the entire tissue (exposed/hardened and unexposed/unhardened) parts are all brought into direct contact with the final support paper. Then in the warm water development bath, the unhardened gelatin melts and washes away. Since this gelatin has some sensitizer mixed in with it, the sensitizer just diffuses into the gelatin sizing of the final support paper. Then, afterwards, as the print is exposed to UV light (lying around on my desk etc.), the sensitizer turns brown. I'm pretty sure that during development, most of the sensitizer is still soluble iron compounds, and that the iron hydroxide/rust only forms after a while. Well, mostly.
No, it seems to be limited to the gelatin sizing, only. Perhaps the iron compounds also permeate between the paper fibers, but wash away as well. I imagine mobility is much more limited in the gelatin layer.
The paper is likely alkaline buffered. The water is not excessively hard, but does leave some scale upon drying, so it's slightly alkaline. I have not yet tried acidifying either, but either can work. Since the problem seems to be mostly limited to the gelatin sizing, I imagine it's even conceivable to acidify the sizing only.
I haven't put much effort or thought into it yet, because for my purposes, I'm really only interested in a double transfer process where the intermediate support is a dimensionally stable polymer film. Since this won't have a staining issue itself, the problem will automatically be reduced to stain in the image-forming gelatin itself. This would make the whole clearing issue a lot less challenging. For single transfers, it's a different ballgame.
So you are in a catch-22 situation
It's kind of hard keep track of all these different scenarios in carbon printing.
Niranjan,
Attempting to half-tone directly in the image via photoshop will lead to artifacts, as it will compete with the printer’s own half-toning algorithm. You would need dedicated software to take control of the printer, even then there are limitations as koraks points out. If you find a work around I would be interested to know.
OK...I played with it a bit. Took a 11-steps wedge and converted using PS via bitmap and printed on a glossy paper with 360 pixel/inch and as far as I can make out under 10X, the pattern on the paper is quite faithful to that on the screen, glitches and all. The way I printed did not involve any of the drivers - by what is known as Null Transform - which is fancy term for telling PS the printer is managing color and telling the printer PS is. I print all my diginegs that way. I am not sure if that is playing a role here or not. PS is also doing a pretty good job of making finer mesh of 720 pixel/inch (from the vantage of my rudimentary knowledge) that I haven't printed yet.
Here are the 2 files:
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Niranjan.
For whatever this is worth....
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