Cyanotype already blue before exposure

LochNesse · May 27, 2020

I've been trying to make some cyanotypes with the traditional formula, but didn't have access to ferric ammonium citrate, and found this alternative formula by the RSC instead:
3g of iron(III) chloride-hexahydrate
3g citric acid
4.5g ammonium carbonate
in 100cm3 of water,
(I'm assuming this makes the ferric ammonium citrate in situ, but honestly not really sure)
then mixed with the 5g of the traditional potassium hexacyanoferrate(III) to form the sensitizer.

However, when I tried to make cyanotypes with this, adding the ammonium carbonate made a semi-dark green colour, and after mixing in the potassium hexacyanoferrate, the sensitizer instantly turned blue rather than the expected yellowish-green so that the paper was coated with a dark blue solution. Even when washing the cyanotype in a water bath after exposure, the blue didn't really change (darker or lighter) other than some slight washing off of the blue in the highlights, though not really turning white. I worry that perhaps the sensitizer was somehow exposed to light, though I'm not sure how that is possible since it was done in a completely dark room. Would previous exposure to light of the components affect the sensitizer when mixed?

Has anyone tried a similar formula where it worked, or have any ideas on where I went wrong/how the sensitizer can be remedied to the supposed yellow-green color? Would any possible humidity in the atmosphere play a factor? Thanks!

nmp · May 27, 2020

Any chance one of the (III) is actually (II)?

I have used oxalic acid instead but no instant blue.

What is RSC, by the way?

LochNesse · May 27, 2020

I don't think so, though I will have to check tomorrow. Thanks for mentioning that, that's one of the variables I hadn't considered yet. If it was, would the colour change be a result of the Fe2+ instantly reacting with the (Fe(CN)6)3+ (or vice versa)?

Also, did you use oxalic acid in place of citric acid in a 1:1 substitute?

RSC is the Royal Society of Chemistry, found the procedure here: https://edu.rsc.org/exhibition-chemistry/the-blueprint-reaction/3010606.article, and it's why I had initially assumed it would work

nmp · May 27, 2020

LochNesse said:
I don't think so, though I will have to check tomorrow. Thanks for mentioning that, that's one of the variables I hadn't considered yet. If it was, would the colour change be a result of the Fe2+ instantly reacting with the (Fe(CN)6)3+ (or vice versa)?

Also, did you use oxalic acid in place of citric acid in a 1:1 substitute?

RSC is the Royal Society of Chemistry, found the procedure here: https://edu.rsc.org/exhibition-chemistry/the-blueprint-reaction/3010606.article, and it's why I had initially assumed it would work

If you had potassium ferrOcyanide, you would have instant blue. Conversely, if you had ferrOUS chloride, it will react with potassium ferrIcyanide to give Prussian blue.

Regarding oxalic acid, I misspoke. I did not mix them all together, but applied the FeCl3/OA on paper, exposed and then developed with K Ferri. Stoichiometrically, it will be 2 moles of FeCl3 with 3 moles of OA which is what I used, although ratio can be played around some. I will try together and see what happens.

RSC...yeah that's what I figured after I asked you.

Luckless · May 27, 2020

Following along out of interest, but my chemistry is too rusty to comment on much with the amount of coffee I've gotten into so far today.

However a quick for sanity's sake check: What's the lighting actually like where you're working?

I have to ask as a friend's lab recently spent an awkwardly long time sorting out some failed reactions out of one station that happened to be next to the bug zapper building management installed without mentioning to anyone, and everyone in the lab managed to not really pay any attention to. [No matter how educated one is, you're never too educated to make silly mistakes...]

nmp · May 27, 2020

FeCl3 by itself is photosensitive so over time it will give Fe+2's. That is a potential source of the problem too.

Vaughn · May 27, 2020

nmp said:
...I did not mix them all together, but applied the FeCl3/OA on paper, exposed and then developed with K Ferri. ...

Sorry for the topic detour, but does this method increase the sensitivity of the material? Thank you.

LochNesse; Terry King of the RPS (the royal society photo people) did a lot of work researching and experimenting with historic processes, including cyanotype (and I believe a camera-speed cyanotye process). But his work would be a good source of info if you can track it down.

nmp · May 27, 2020

Vaughn said:
Sorry for the topic detour, but does this method increase the sensitivity of the material? Thank you.

LochNesse; Terry King of the RPS (the royal society photo people) did a lot of work researching and experimenting with historic processes, including cyanotype (and I believe a camera-speed cyanotye process). But his work would be a good source of info if you can track it down.

Hi, Vaughn:

Sensitivity In comparison to what? FeCl3 by itself is very slow. With oxalic acid it is quite fast. However, I did not do a systematic study - I was just playing around based on Namias' work as I was out of my ferric oxalate at the time. And then had detours of my own...

King's process is based on ferric oxalate, I believe but you won't find much in the way of recipes as they are kept behind a paywall. OP's RSC process is similar to Ware's Simple cyanotype in that the FAC is made in-situ but his starting ingredients are ferric nitrate and ammonia instead of ferric chloride and ammonium carbonate.

:Niranjan.

Vaughn · May 27, 2020

Thanks...cyanotypes are something I might start exploring again. I'll keep it rather simple.

nmp · May 28, 2020

LochNesse said:
I don't think so, though I will have to check tomorrow. Thanks for mentioning that, that's one of the variables I hadn't considered yet. If it was, would the colour change be a result of the Fe2+ instantly reacting with the (Fe(CN)6)3+ (or vice versa)?

Also, did you use oxalic acid in place of citric acid in a 1:1 substitute?

RSC is the Royal Society of Chemistry, found the procedure here: https://edu.rsc.org/exhibition-chemistry/the-blueprint-reaction/3010606.article, and it's why I had initially assumed it would work

So there may be more going on than meets the eye (at least mine.....)

Did some experiments:

Took my FeCl3/OA 1:1 mixture and added some K Ferri - instant color change to an intense green, not blue. Coated a piece of paper and got a dense green coating. Exposed a part of it and dunked it in water. The exposed part became intense blue and the unexposed part stayed pretty much the same, i.e. did not wash off immediately, but after leaving it out and about for a while changed to light blue as well.

Next I tried making the same formulation as above with citric acid. But I don't have ammonium carbonate (and out of NH3 as well.) So I left it out and mixed the FeCl3 with citric acid. Nice and clear solution. To that I added the K Ferri. Viola! same thing, the solution turned intense green as well. Again not blue.

I am by no means an inorganic chemist, but it seems to me something else is going on. These molecules are notorious for making all kinds of complexations/coordinations with different colors so I suspect some of that might be going on here. It is interesting that in the video, the instructor left out the precise instant of mixing the K Ferri with the rest. Otherwise we would have known whether or not he got a clear solution or not.

The intrigue continues......

:Niranjan.

LochNesse · May 28, 2020

Thanks everyone for your help and suggestions! Turns out Niranjan was right, there was a mislabel of chemicals and the potassium ferricyanide was most likely potassium ferrocyanide (though I’m honestly not sure what it was). The fact it wasn’t red should have been a dead giveaway, but I had embarrassingly managed to convince myself that working under a red light would cancel out the colour to show white.

I’ve switched out the dodgy chemical for actual potassium ferricyanide, and everything works well now! Guess I'll just consider it a learning experience haha, and a good reminder to double check everything first, particularly the things that are usually overlooked and taken for granted

Donald Qualls · May 29, 2020

Don't toss that ferrOcyanide yet! There's a cyano formula that makes direct positive images that uses that chemical. I *think* it goes on blue and bleaches white with UV exposure, but I've never actually used it and it's been a long time since I read about it...

nmp · May 29, 2020

LochNesse said:
Thanks everyone for your help and suggestions! Turns out Niranjan was right, there was a mislabel of chemicals and the potassium ferricyanide was most likely potassium ferrocyanide (though I’m honestly not sure what it was). The fact it wasn’t red should have been a dead giveaway, but I had embarrassingly managed to convince myself that working under a red light would cancel out the colour to show white.

I’ve switched out the dodgy chemical for actual potassium ferricyanide, and everything works well now! Guess I'll just consider it a learning experience haha, and a good reminder to double check everything first, particularly the things that are usually overlooked and taken for granted

Good to know you figured it out. Colors can be deceiving in safelight so I have learned myself at times.

Thanks for pointing out this new method, by the way. I had not seen it before so I am intrigued to try it myself. I am going to get some ammonium carbonate (apparently it is also called baker's carbonate as it is used in baking.) This is a good substitute for ammonia - I hate the fumes.

Some questions:

How does the solution look, once all the proper ingredients are mixed in. Green? Light, Dark?

When you coat on the paper, does it look lemon yellow like the traditional formula using commercial FAC?

Finally, if you have printed with the classic formula, hoe does this one compare - in terms of speed Dmax, staining, fogging, whites clearing etc.

Do share your experience if you can.

Thanks!

:Niranjan.

LochNesse · May 31, 2020

I've only tried printing with solids objects on top, no negatives yet, but I can answer a few of those questions

The solution is a fairly dark green when everything is mixed in, though that's only in "large" volumes of around 100mL. When only a small amount is used to coat the paper, it's instead a lighter yellow-green colour, almost lime, but fairly similar to the traditional formula.

Haven't printed with the classic formula, but for this modified formula, the edges of the highlights are pretty sharp with little staining, though occasionally I won't be able to wash off the yellow in the highlights completely - there'll be a light yellow tint, though it's only be noticeable against the white of the paper; against the blue it's pretty much white. I might try adding some citric acid to see how that goes, but I'll have to wait until Monday to try that.

Can't say much for speed either relative to the classic formula as I haven't tried it, but if it helps it takes around 45 minutes in my light box with a UV tube of 8W to develop properly (made a light box to give some semblance of replicability)

Hopefully this helps!

Vaughn · May 31, 2020

Yellow tint -- if it is iron (like the yellow tint in pt/pd prints), it might like a similar clearing bath, post development -- Sodium sulfite and EDTA is what I use (or Kodak HCA and a little extra EDTA).

nmp · May 31, 2020

LochNesse said:
I've only tried printing with solids objects on top, no negatives yet, but I can answer a few of those questions

The solution is a fairly dark green when everything is mixed in, though that's only in "large" volumes of around 100mL. When only a small amount is used to coat the paper, it's instead a lighter yellow-green colour, almost lime, but fairly similar to the traditional formula.

Haven't printed with the classic formula, but for this modified formula, the edges of the highlights are pretty sharp with little staining, though occasionally I won't be able to wash off the yellow in the highlights completely - there'll be a light yellow tint, though it's only be noticeable against the white of the paper; against the blue it's pretty much white. I might try adding some citric acid to see how that goes, but I'll have to wait until Monday to try that.

Can't say much for speed either relative to the classic formula as I haven't tried it, but if it helps it takes around 45 minutes in my light box with a UV tube of 8W to develop properly (made a light box to give some semblance of replicability)

Hopefully this helps!

Thanks for the update....definitely helpful. I am particularly interested if this method gives better fogging characteristics (blue staining) over the classic formula which I find hard to achieve unless sacrificing a good bit of Dmax. The yellow stain is the result of remnant of the iron compounds. Citric acid wash will be helpful for that. Considering this method behaves the same way as the classic chemistry, If you start with a citric acid wash, instead of the plain water, it will also increase the propensity for blue stain in the white areas in addition to improving the Dmax.

I should have my ammonium carbonate in a few days....It will be interesting to see how that works out.

:Niranjan.

P.S. Welcome to Photrio by the way, noticed this was your first post here.

nmp · May 31, 2020

Vaughn said:
Yellow tint -- if it is iron (like the yellow tint in pt/pd prints), it might like a similar clearing bath, post development -- Sodium sulfite and EDTA is what I use (or Kodak HCA and a little extra EDTA).

I don't know what EDTA would do, but sodium sulfite by itself, being basic in nature, would most likely bleach Prussian blue.

Vaughn · May 31, 2020

Thanks -- extended washes are not great for cyanotypes, either...having left one in the water overnight. EDTA is a cleating agent...one might try a tablespoon in a liter or two of a 1 to 3% bath of Citric acid as a wash aid to get rid of the yellow. Warning...have absolutely no idea if it would work or harm. Using experience in Pt/pd printing and transferring that to cyanotype is a chancy thing.

nmp · May 31, 2020

Vaughn said:
Thanks -- extended washes are not great for cyanotypes, either...having left one in the water overnight. EDTA is a cleating agent...one might try a tablespoon in a liter or two of a 1 to 3% bath of Citric acid as a wash aid to get rid of the yellow. Warning...have absolutely no idea if it would work or harm. Using experience in Pt/pd printing and transferring that to cyanotype is a chancy thing.

Regarding extended washes, it is particularly true if you happen to have tap water that is neutral to alkaline. In my tests based on a short period of time (I didn't do overnight though) I have found that if you start with citric acid wash first, then subsequent plain water washing caused less bleaching - with longer the first wash, the better. On the other hand with all tap water washing, even though my city water is in the 6-7 pH range, the fading within the same period of time still had not plateaued.

Good thing about pt/pd is one can mess about it and not endanger the metal image short of dunking in aqua regia, whereas a cyanotype will fade on you if you look at it sideways...

:Niranjan.

Cyanotype already blue before exposure

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