Iron Blue Toner Formula

Hello,

Some time ago I found on Jack's Photographic and Chemistry Site a formula for a blue toner called Ansco 241:
ferric ammonium citrate 8g
potassium ferricyanide 8g
tartaric acid 37g
water 1l

I tried it, and it worked fine.
Now, while browsing an old catalog of Agfa formulae I stumbled upon the same formula, this time called Agfa 241, but slightly changed:

ferric ammonium citrate 8g
potassium ferricyanide 8g
acetic acid 28% 265ml
water 1l

So, it seems to me that this toner requires a weak acid, but not necessarily tartaric. This is good news to me, as my supply of tartaric acid is pretty limited and I'd like to save it for vandyke prints.
If that's the case, then I think citric acid should work just as well. But I don't know the equivalent quantity. I tried to use 40g of citric acid, and the resulting toner seemed to work fine, though my tests weren't thorough enough to draw a definite conclusion. Besides, I don't know how the quantity of acid affects other things, like the toner's keeping properties, or the image stability, and so on.

First, what purpose does the tartaric acid serve in this formula, and can this purpose be served just as well by any other weak acid? I'm particularly interested in citric acid, because I have lots of it.
Second, supposing citric acid worked fine, what quantity of citric acid would be equivalent to 37g of tartaric acid, or to 265ml of acetic acid 28%?

Thank you.

I have no idea about the substitution, I have never seen a blue toner using citric acid. More: many blue toners use strong acid (hydrochloric/sulphuric). If you do a quick search on www.archive.org for "photographic fact and formulas" you can find many toner formulas inside (there are also many other old books on photo chemistry).
By the way, you had no problems with staining on FB paper?
Regards
A.

The formula I have used comes from Elementary Photographic Chemistry, Eastman Kodak Company, 1941 (it is not in the 1936 edition).

Iron Toning bath for Blue Tones -- Formula T-12

Ferric Ammonium Citrate.....4 grams
Oxalic Acid ........................4 grams
Potassium Ferricyanide........4 grams
Water to make....................1 liter

Mix each chemical separately in water (about 250ml), then combine and add water to make 1 liter

In both cases, the tartaric acid and acetic acid solution merely serve to adjust the pH to be accidic enough for the reaction. On principle I avoid using tartaric acid whenever possible. It is produced as a byproduct of wine making, and I have had some problems with purity when using it in the lab.

well, you can find it pharmaceutical or analytical grade (pricey)

Antonio Banfi said:

well, you can find it pharmaceutical or analytical grade (pricey)

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I'm using analytical grade (>99% pure) and still find that there are impurities that interfere with reactions. Probably not a big deal for photo chemistry, but when there's an easy alternative, I would reccomend it.

Cheers,
Bryan

Thanks, guys.

I've found another formula called GT-14 on the same site, here.
While all these formulae are slightly different from one another, they have one thing in common. They're all based on equal quantities of ferric ammonium citrate and ferricyanide, plus some weak acid, be it tartaric, acetic or oxalic.

By the way, you had no problems with staining on FB paper?

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No, I had no stains so far. At first glance the toning seems to extend from the dark areas into the surrounding light areas, giving an impression of staining, but this effect disappears later, during washing. Complete toning takes very little time, no more than about twenty seconds, and tends to lower the overall density of the print. I think the print should be a little overexposed.

In both cases, the tartaric acid and acetic acid solution merely serve to adjust the pH to be accidic enough for the reaction.

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Thanks, that's what I wanted to know. In that case I guess citric acid should do, too. But in what quantity? :confused:

VladSoare said:

Thanks, guys.
Thanks, that's what I wanted to know. In that case I guess citric acid should do, too. But in what quantity? :confused:

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Hard to say without knowing the target pH, especially since there are other acidic/basic components, but if an equal mass substitution worked, it should be fine.

I may mix up some after reading this, and I will use a pH meter to find the proper amount of citric acid to add. May be a few weeks, but I'll post once I find out.

The reason for the acid is that Prussian blue is unstable in an alkaline environment. I have formulas for iron blue toners using all sorts of acids except citric. Acetic, tartaric, and oxalic are common, as are 2-4 ml per liter of concentrated sulfuric, hydrochloric, or nitric. The strangest called for fluorosilicilic acid. One called for sodium bisulfate, which is a substitute for sulfuric acid. Apparently the choice of acid affects the tone you get to some extent. Because it was easy, I decided to try a blue tone using citric acid. I used:

Ferric ammonium citrate 8 g
Potassium ferricyanide 8 g
Citric acid 8 g

When I added the citric acid, some blue color, possibly colloidal Prussian blue, appeared. This made me wonder about the stability of the solution. I think I did not use enough acid to do things right. In any case, I tried toning a print. It produced a dark blue-green tone with noticeable intensification. So citric acid works, but I'm not sure how well.

As it happens, I tried working with an Iron blue toner today (the formula @ http://www.jackspcs.com/ibt.htm) and while it produced a strong blue tone on the ILFORD Multigrade FB Gloss paper I was using, washing afterwards was uneven probably due to the unstable Prussian Blue. I see from re-reading the article that a slightly acidified wash step is recommended.

Tom

Tom, I got some stabilizing effect using 1/2 cc of HCL 37% in 1 liter of water.
Regards
A.

I've always used oxalic acid for blue toner.

2F/2F said:

I've always used oxalic acid for blue toner.

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Same here -- the blue toner formula I gave earlier works great and the highlights wash out nicely -- and doesn't use much of the raw chemicals.