Cyanotype weird emulsion

henrit

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Hi, folks,

Since the green ferric ammonium citrate is not promptly available in our marketplace, I decided to try Mike Ware's New Cyanotype formula, making it myself. I tried my best to follow all directions, especially those about temperature and ambient light control, within the somewhat limited resources of my working place.

Much to my surprise, the "yellow-green coloured solution", as described by Ware, did never show up; instead, I got a bold, dark Prussian blue solution (see pictures).

I tried this blue emulsion anyway, and: 1. printout image is negative (see picture), and washing out is near zero; 2. image slowly turns to positive, but so faint (no matter what the exposure time has been) it's barely visible (see picture).

Bottom line is, I made a strange emulsion, completely unsuitable for cyanotype printing. Please, any clue of what is happening?
 

koraks

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Not sure what went wrong here, but it did go wrong quite spectacularly. Can you describe exactly what you did and which ingredients you used?
 
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henrit

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and Niranjan:
I bought the ferri from a local chemical retailer

and the FAO from a big company which I think is reliable


I started by dissolving 10g ferricianate in 20 ml of hot destilled water; I kept the ready solution inside a thermal box.
Then, I dissolved the FAO (30g) in 30 ml of hot water (not an easy task). I had no means of measuring the temperatures, so I just used a pretty hot destilled water. I added ammonium dichromate (20%, 0.5ml), mixed 1 to 2 (with stirring).
That moment, the blue color appeared immediately, and letting it sit in a dark place for 1 1/2 hour to cool down and cristalize did not change anything.
 

nmp

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Oops! Henrit, looks like you got potassium ferrOcyanide which is K4 while you need potassium ferrIcyanide which is K3. The result of a reaction of ferrocyanide with FAO would be ferric ferrocyanide, Prussian Blue.

Hopefully the mistake was on the supplier's part and will give you a replacement...
 
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henrit

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That’s it, Niranjan! I really never paid attention to this tiny detail... I’m afraid the mistake was mine, since I’m almost a chemistry illiterate. But now everything is clear. Thanks so much, Niranjan!
 

koraks

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Yep, good catch @nmp, that's also what I immediately saw...
@henrit always look at the CAS numbers, they're standardized internationally! Each chemical has its unique CAS.
Fortunately, some ferricyanide is easy to obtain!
 

nmp

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henrit said:
That’s it, Niranjan! I really never paid attention to this tiny detail... I’m afraid the mistake was mine, since I’m almost a chemistry illiterate. But now everything is clear. Thanks so much, Niranjan!
Click to expand...

You are welcome. Luckily you posted the pictures of the chemical bottles. Otherwise we would have been chasing some other ghosts. Ferro-Ferri...It is a very easy mistake to make.

Good luck!

:Niranjan.
 
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