Cyanotype: first bath and development questions

Hi there,

I have some questions regarding the cyanotype development process.

1 - I would like a clarification about the first bath or development bath :

• What is its purpose ?
• How can I develop in the first bath in order to gain contrast (I mean to obtain a strong blue) ?

I’m a little bit confused with the acidic first bath.
I’m not sure if it tends to lower or increase the contrast of the blue.

Sometime, I read to use citric acid in the first bath to lower the contrast (so I understand: a clearer cyanotype) and sometimes it’s the complete opposite.

Can you enlighten me in that matter ?

2 - What is the real difference with the use of the different acids ?

• Citric acid,
• Or other mineral acids like nitric or hydrochloric at ~1% dilution ?

• Is there a difference in the final developed print ? (Different blue maybe ?)

3- Another question about increasing the deep of the blue:

I have read that a drop of a 1% ammonium dichromate in the first bath (?) could greatly help to increase the deepness of the blue.

• Is that true ?
• If somebody uses this trick, what is the number of drops to add in the first bath ?

You understand I’m trying to obtain the strongest blue with my prints.

I know that’s a lot a question !
Thank you all for your help.

I work with the Mike Ware new formula that I’ve previously made.
My paper is Arches Platine (new batch) or alkaline-free Asian paper (made from mulberry) with a neutral PH.

I use traditional formula for cyano's, wash is with plain tap water. To intensify the blue, simply add an ounce or two of hydrogen peroxide in with the wash. You can rinse with straight H202 after washing, it doesn't matter. You can buy the hydrogen peroxide at any pharmacy or grocery.

i use a 1% sulphamic acid for the developer bath for about 1.5 min.; then face down in a tray of plain water(non chlorinated) for about 5 min.. Ware recommends an acidic first development bath. Are you trying to match your negatives to the ES of the sensitizer? Ware's formula is of long scale. My batches have tested out from 1.7 to 2.1 depending on paper and treatment of paper prior to coating and exposing.

Hydrogen peroxide doesn't actually deepen the blue of a cyanotype, it only serves to increase the rate at which the oxidation takes place in forming the blue pigment.
So a cyanotype which is washed and allowed to dry fully will eventually dry down to the same depth of colour as one which has been placed in a bath of peroxide solution.

This is quite well documented by various alt-process authors, and I've verified it myself by testing and experience,

Just as a note on the use of Citric acid in the first wash in iron-based processes (cyanotype, VDB, Namias Sepia etc.).

It is often recommended to use an acidic first wash, and to use Citric acid for that purpose. I only recently discovered that Citric acid is what is known as a siderophore. Which is to say that it is an iron chelating chemical which allows soluble iron complexes to form. The important bit is that these are soluble, so making it easier to fully wash the paper free of iron which might otherwise cause staining or fogging. Other acids either don't do this at all, or don't do it anywhere near as efficiently as Citric acid.

As to the other questions of the OP, I'd guess many of them can be answered by him through experiment. There are rarely hard-and-fast answers in alt-processes when it comes to image colour or "quality".

Fwiw I have noticed some differences in image colour depending if I wash in Citric vs. Sulfuric vs. whateveric acid. But I couldn't really describe them except to say Sulfuric looks a bit more cyan-y. But it's a year or two since I tried that so maybe I'm misremembering?

Ok I was a little bit slower… but here is my answer…

Usually the (citric) acid is used to lower the pH value of the tap water, which might be necessary since the Prussian blue complex (that’s the colour formed in the cyanotype process) will tend to decompose in an alkaline environment.

If the citric acid is used in the sensitizer it might prevent fogging. (at least in Mike Wares sensitizer)

Of course you can add one final bath in hydrogen peroxide, as Rick A pointed out, but be aware that it only accelerates the natural darkening of the picture. (H2O2 oxidises the Prussian white complex to Prussian blue, a process that also takes place under normal air exposure.)

Mike Wares Cyanomicon basically covers everything you need to know about the cyanotype process. You can download it from his personal website…

http://www.mikeware.co.uk/mikeware/downloads.html

Prussian blue is also known under various different names (at least in German: Preusischblau Pariserblau, Turnbulls Blau, etc.), more important it can show different shades/tones of blue, depending on the reaction path used to produce it.

-Martin-

Thank you for all your responses.

I was aware of the Hydrogen peroxide effect on the rate at which the oxidation takes place in forming the blue pigment.
I’ve also verified it, this is very useful to have a quick look of the final print.

On the cyanomicon from Mike Ware, I read that an acidic first bath is recommended.

I was wondering if there were a significant change on the blue with different sorts of acid,
and which is the best to produce a very deep blue like I can see from other photographers sometimes.
It is hard to determine I think…

I’ve experienced a very nice « velvet » blue, near of the ultramarine with a slight shift toward purple on Arches Platine paper.

What I’m trying to achieve is a cyanotype with the deepest possible blue.
Like these examples :

• http://www.vividvisions.co.uk/album...ints/slides/ARGYRANTHEMUM by Bob Marshall.jpg
• http://altphotoprocess.blogspot.fr/2011/07/latest-cyanotype-prints.html

It’s very difficult for me to approach these results.

My water is rock solid (~PH 8) so, I’ve made a process to reach a PH of 5.5 - 6 with citric acid in the baths.

pdeeh said:

It is often recommended to use an acidic first wash, and to use Citric acid for that purpose. I only recently discovered that Citric acid is what is known as a siderophore. Which is to say that it is an iron chelating chemical which allows soluble iron complexes to form. The important bit is that these are soluble, so making it easier to fully wash the paper free of iron which might otherwise cause staining or fogging. Other acids either don't do this at all, or don't do it anywhere near as efficiently as Citric acid.

Click to expand...

This is very interesting.
However I am not sure I fully understand the meaning of this.

Is this meant that a citric acid bath tends to "dilute" (iron chelating) the blue ?

Tetium said:

Is this meant that a citric acid bath tends to "dilute" (iron chelating) the blue ?

Click to expand...

No, I don't believe it does, however I cannot explain the chemistry of it in any more detail than I have already. But I have not seen less intense blues from using a Citric acid wash than from not using one. But as I said above, your very best bet is to test for yourself and see. We can spend a great deal of time theorising and hypothesising, but empirical evidence provides the final answers.

The formation of soluble iron complexes so that they can be washed out might be more important in other "siderotypes" (like Vandyke Brown & Kallitypes) where retained iron can cause staining problems.

I'm sorry to say that I simply don't have the qualifications or experience to explain further - you will have to hope that a real chemist comes along and takes an interest!

Tetium said:

What I’m trying to achieve is a cyanotype with the deepest possible blue.
Like these examples :

Click to expand...

please remember that how something looks in your web browser is not the same as it will look in the hand. Even allowing for digital "tweaking" to colours and contrast, remember that prints are viewed by reflected light and web-images by transmitted light.

As far as I know, it is even impossible to display Prussian blue accurately on an RGB display since its colour is usually outside of the monitors Gamut, you can display only something that’s similar to what Prussian blue would look like…

I use the classic cyanotype formula. My initial bath is 1 part household white vinegar (5%) to 3 parts tap water. After about 1 minute I go into clean tap water for the remainder. I had read that a mix of 1:1 vinegar/water offered a bit of contrast control (a little less contrast) for the classic process but I found that 1:1 caused my paper to not clear well - it stained blue slightly...so I cut the vinegar to 25% and that works well for me. I can tell a noticeable lowering of contrast with this vinegar/water mix. Vinegar is cheep - I get a gallon for about $2.60.

Many thanks for all your replies.
This is such a great place !

As pdeeh said ; « empirical evidences provides final answers » and it’s totally true.
I am also very confident that APUG and it’s aficionados is the best start place to gain knowledge.

Thanks to remind me the difference between reflected and transmitted light,
I'd indeed forgotten this fact in my search for a better blue.

See you later for other questions !

I’am still looking for the best workflow for my cyanotypes.
I chosen New Cyanotype formula.
Papers are still difficult to choose. But I Like ‘Terschelling’ it’s perfect available at local shop for reasonable price here in The Netherlands. I tried to buy Herschel from ruscombepaper. But the webshop does not work, they don’t answer my e-mail and this paper cost 3x the price of Terschelling.
Today I did experiment what’s the best ‘developer’.
All same time from my TL UV source 125 seconds
Used an test negative I made with an photocopier on overhead sheet.

I tried (this is what I had at home):
In the Photo attachment seen from left to right !
Tap water measured PH 8
Nitric acid 0,5 % measured PH 1.7
Oxalic acid 0,1 Mol /L measured PH 1.9
Citric acid 0,1 Mol /L measured PH 2.5
Acetic acid 0,1 Mol /L measured PH 3.4

Tap water is not OK very slight bleaching effect of only lightly exposed regions, resulting in a higher contrast and apparent slower speed

Acetic acid, Citric acid, Oxalic acid are near the same
Nitric acid is much darker. Why ???
Mike ware advice is the use of nitric acid. But the disadvantage is that it is not available for a private here in The Netherlands. And the other acids I can easy buy at the supermarket or drug store.
I’am still not sure what the best acid I can use. Acetic acid is cheap and buy 5L for €1,50.

Image runoff is different by each acid. See Photo from the developer trays .

I use the Ware sensitizer also.
Arches palatine has been working well for me with no pre treatment other than humidify the paper for 10 minutes prior to coating. 1% sulfamic acid also works well as a developer. There is a thread here on APUG about using sulfamic acid that may be of interest to you.

Best,
J

Thanks for your answer. Can you explain why you humidifying the paper ? And how you humidifying the paper ? I have not read about this approach yet.
Found this http://cool.conservation-us.org/coolaic/sg/bpg/annual/v21/bp21-15.pdf but is that what you do ?

sulfamic acid is indeed one of the chemicals I wan’t to order next time.

I can’t find an shop who sells Arches platine in The Netherlands. But just wrote my local shop if they can ordered this paper from the manufacturer. I found an online webshop where I can buy the paper in Germany. But shipping cost overseas ‘ll be higher for already expensive paper, so that’s not my first choice.

mug, when I lived in NL I used the cheap water color paper that my daughters used for school (from HEMA), because it was not buffered (slightly acidic) images were darker but sometimes it was blotchy
Strahmore aquarelpapier was easy to find and it is much nicer, color spreads better and spread is very even

As some people said before, the hydrogen peroxide doesn't make the blue deeper than when the print dries completely. The acid first bath just makes the prussian blue to form on a better evironment. (The cyanotype chemistry likes acidic paper, rather than neutral or alkaline).
For my prints I use a paper that is used for making publications at school. It is very thin, white, and I've never measured the pH of it, but it isn't alkaline. It may be neutral. I found that using the peroxide trick doesn't help me much of a thing to deepen the blues, and if I leave the print for too long (say two, three seconds), it bleaches! So I'm careful, and mostly paicient for the print to dry completely. Also, my tap water has a pH of around 6, so it doesn't help my prints. That's why you use an acid into the bath, to "cancel" the alkalinity of the tap water, and so to not loose any blue formed.

The thing that helps me the most with the strength of the blue is to have... The correct exposure!
Uderexposed cyanotypes may look okay, but the blue may be a disaster. This happens because instead of forming prussian blue, there is turnbull's blue, which is very deep, but not useful. My advice, is to make test strips for each print, having a standard time for reference. Always write at least the date, exp time and hour of the day (if you use sunlight) somewhere, so as to track what are the best results.
Other thing that may help is to concentrate the amount of ferric salts present in solution A. That will give longer exposure times, but deeper blues, since there'll be more prussian blue pigment present. Maybe concentrating also the ferricyanide? I guess so... Haven't tried.
And last, don't ever mix any mineral acid with prussian blue or ferricyanide/ ferrocyanide at concentrations higher than 1%. This will create prussic acid aka as cyanide gas. The purpose of a HCl second bath is to further remove unexposed iron salts. But I found It wasn't really neccesary, unless you use a salt that's pretty much insoluble, like ferric sulphate.

Hope that helps.

I use the traditional formula. I use HPR paper, which does not require acidification. After clearing the print in straight tap water, I pour straight hydrogen peroxide over the print for a few seconds. Then wash the print with tap water. Bob's your uncle.