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.
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He says "warm 30-32C" which wouldn't make sense. That is hardly warm - particularly in Texas, it might be the tap water temperature. I would say it is typo. If 40-42 is the correct universally known development temperature then it would a weird coincidence if 30-32C is what he meant.
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? I wonder what role does that play beyond simply increasing the photo-efficiency of FAC.
:Niranjan.
The first batch I made was not acidified, although I already picked up somewhere (can't recall where, though) that optimum sensitivity for ferric carbon should be around pH4.0. The current batch I'm drying now is acidified, but not with oxalic acid. I used a little hydrochloric acid instead, and frankly didn't measure pH but just added a little bit (0.5ml 10% HCl to 100ml glop).
I suspect that Saidane might be using oxalic acid specifically because the optimal sensitivity with ferric carbon furthermore is at roughly equal weight ratios of ferric ammonium citrate and ferric ammonium oxalate. Perhaps that's why he uses only FAC, but acidifies with oxalic acid - just guessing here.
I based my formulas on this post by Sandy King: https://groups.io/g/carbon/message/10252
It's along similar lines as what he mentions in his 2019 book, although the formula they give there on page 139 is somewhat different. The important ratio seems to be that 25% of the dry gelatin weight in FAC (or FAC + FAO) must be added. That's a lot of sensitizer btw, suggesting it's rather inefficient. It's almost two orders of magnitude more sensitizer than when DAS.
There's another difference - he is using the FAC the old fashioned way, like how you would sensitize with dichromate. It's only 3.5 gm in a 100 ml of water+acetone. Why did he not go for the ultimate simplicity of incorporating it in the glop? May be this worked better somehow.
:Niranjan.
Yeah, I wondered about that, too. Might have something to do with contrast control. I doubt it means much in terms of the mechanics of the transfer. Easy enough to give it a try; I have in mind doing just that. Maybe tomorrow, if I manage to remember it 
Okay, I gave the ferric carbon thing another go. I poured some tissues with ferric ammonium citrate and ferric ammonium oxalate added to them and a little HCl to acidify it. Initially I tried transferring to an albumen subbed transparency and that failed. The relief hardens alright and it develops too, but it won't adhere to the support, so it basically just drifts off like a polaroid emulsion lift.
Just now I tried transferring to gelatin-sized paper (hardened with chrome alum) and that sort of works:
In the lower left corner there's some fine detail missing, but most of the image seems to have transferred just fine. There's a lot of yellow-brown sensitizer stain and contrast is wonky as well. The trunk looks almost like a duotone instead of continuous tone. This may have to do in part with the sensitizer stain; let's see if I can clear that out once the print dries and hardens.
What this tells me so far is that ferric carbon can work similar to regular carbon, but it's more trick to transfer. Perhaps it could even be made to work transferring to a transparency that's fairly heavily gelatin-sized. If that works, it would in principle work for multiple transfers and hence potentially for color as well. Maybe I'll give it a try one of these days if I can put myself to making a batch of gelatin-sized transparencies.
I'm also drying a brush-sensitized tissue with a 1.5% FAC + 1.5% FAO sensitizer. I used 2.5ml or so for a 5x7" tissue to make a 4x5" print. Let's see how that turns out, but the sensitizer-incorporated tissue is a more important step IMO since it is inherently more consistent and convenient than a brush-sensitized workflow.
Just now I tried transferring to gelatin-sized paper (hardened with chrome alum) and that sort of works:
In the lower left corner there's some fine detail missing, but most of the image seems to have transferred just fine. There's a lot of yellow-brown sensitizer stain and contrast is wonky as well. The trunk looks almost like a duotone instead of continuous tone. This may have to do in part with the sensitizer stain; let's see if I can clear that out once the print dries and hardens.
What this tells me so far is that ferric carbon can work similar to regular carbon, but it's more trick to transfer. Perhaps it could even be made to work transferring to a transparency that's fairly heavily gelatin-sized. If that works, it would in principle work for multiple transfers and hence potentially for color as well. Maybe I'll give it a try one of these days if I can put myself to making a batch of gelatin-sized transparencies.
I'm also drying a brush-sensitized tissue with a 1.5% FAC + 1.5% FAO sensitizer. I used 2.5ml or so for a 5x7" tissue to make a 4x5" print. Let's see how that turns out, but the sensitizer-incorporated tissue is a more important step IMO since it is inherently more consistent and convenient than a brush-sensitized workflow.
Ran across this post on Facebook recently. Apparently N-METHYL-4-(P-FORMYLSTYRYL)PYRIDINIUM METHYLSULFATE) or SBQ can be used in conjuction with PVA for what appears to be non-toxic Gum-like printing. Not much details though, but looks promising and could possibly be an alternative for non-toxic Gum Printing.
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 - 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?
Paper seems to make the biggest difference. Bockingford hot pressed 300g watercolour
has the least issue with staining For me. I also additionally size it with liquitex matte medium at a dilution of 1:10. This seems to keep things clean. Also I’ve learned that some watercolours just stain like crazy and are just to be avoided.
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.
Have you tried Ferric Carbon double transfer Koraks? I.e. transferring onto an Albumenized Mylar or similar. That at least would mean you could possibly clear the stain with something before getting the image on paper. I've heard varying reports of how well Double Transfer works with Ferric Carbon though.
Yes, it doesn't work. The relief doesn't adhere to the subbed transparency. So far I can only get a dodgy transfer directly to a fairly heavily gelatin sized paper support.
Could you point me to the more positive ones? So far the only reports I'm aware of are that double transfer isn't possible with ferric carbon. I'd be very interested to read about successful attempts!
Koraks-
In Sandy's (and others) Carbon Printing book I believe it mentions that Ferric Carbon on an albumen substrate should work, but I have seen no confirmed reports from anyone that it actually does. 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?)
In Sandy's (and others) Carbon Printing book I believe it mentions that Ferric Carbon on an albumen substrate should work, but I have seen no confirmed reports from anyone that it actually does. 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?)
Yes, but it's a different procedure than standard double transfer. In the book they propose pouring the tissue onto albumen-subbed polyester, exposing through the base of the tissue and developing it on the polyester. After drying and clearing it can then be transferred to a final support. I have not yet tried this support and it's not very high on my list due to the inevitable degradation of detail that occurs when exposing through the base of the tissue support. Especially with halftone screen negatives this will be problematic since it'll result in dot gain.
Yes, that I've read too. No gluing necessary; simply mount on top of a white support (or any other color desired!) I.e. a picture frame with a sheet of paper, the film-with-carbon-relief and then the picture glass all clamped together should work A-OK.
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. If that's the case, it becomes increasingly difficult to clear after the paper is dried where it can take the form of hydrated iron oxide. This kind of staining does not occur in cyanotype, for example where FAC is coated straight onto the paper, particularly if acidic wash water is used (which might favor blue stains, but not yellow.) So why here? Are the stains also on the back side of the paper? Is the paper alkaline, or the tap water? Can you acidify one or both?
Oxalic acid is much better than citric acid to remove the Fe(OH)3 stains, by the way.
:Niranjan
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.
Got it. So you are in a catch-22 situation. You would rather use a stable polyester type support at this stage - but so far it has alluded good enough adhesion to the tissue. Sized paper has the adhesion, but stains - which would be inportant deal with if that was your final support.
It's kind of hard keep track of all these different scenarios in carbon printing. Thanks for the explanations.
:Niranjan.
When it comes to ferric sensitizers, yes. My focus right now is on what most color carbon printers do: use DAS. Since I figured out how to get that to work, it makes all the more sense to follow their lead. Still, I like the appeal of ferric for economic and availability reasons.
Man, you tell me...then there's the wide range of compounds barely touched upon in various discussions. I'm sure there are lots of interesting avenues we should be able to explore when studying conceptually similar colloid hardening and/or crosslinking processes in industry.
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:
Niranjan.
An update:
I printed the 720 ppi chart above the same way from PS and that one didn't come out as good. Seems that something did mess it up somewhat - the basic pattern looks similar but the dots seem to be mushed up a bit into each other, losing their individual character.
I then went and printed it from QTRgui (2880 ppi super mode, unidirectional) and the result was much more faithful to the original. Dithered Algorithm option selected was "Ordered," - don't know what that does, if anything, as it related to halftones.
For whatever this is worth....
:Niranjan.
Oh, this is very relevant indeed. It's currently also being discussed/experimented with here: https://groups.io/g/carbon/topic/first_approach_to_color/97727051
I'm not sure if you ever post there, but if you do have an account, I'm sure Sandy and others would be interested to read about these experiments of yours as well!
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