The cyanotype boost process

The cyanotype boost process, or how to obtain darker and deeper indigo-blue hues on your cyanotype prints

Many people have asked me how do I make my cyanotype boost process and how can I obtain the results I show. What is the recipe? Is there a silver bullet to achieve such a strong result with cyanotype printing? I truly don’t know. But I can try to explain how do I do it.

My latest cyanotype print production has gathered a nice interest around. In particular, the object of attention is the pretty extended tonal scale that reaches a deep indigo-blue hue. In some cases il looks quite close to black, even if it’s just a deep blue.

Cyanotype boost, a very personal approach

Cyanotype printing is actually a process consisting of a broad amount of formulas and recipes. For what your beliefs are, it’s not standardized nor fixed on stone. Reading here and there, I’ve collected tons of different formulas and recipes for different processes, all leading to the so called Turnball blue and Prussian blue, which are credited to be almost the same compounds and the same colors.

The process I use is based on the classic recipe involving Ammonium Iron(III) Citrate. I have never used oxalate because I know it has some drawbacks which may affect my process. I’ve spent years studying the classic formula and I don’t want to restart everything from the beginning now.

The cyanotype boost process – cyanotype print from 30×40 cm wet plate collodion intensified negative

My basic recipe is the most common one: the ratio ferricyanide to ferric salt is 1:2.5.

I’ve found this interesting study by Alberto Novo on cyanotype recipes which yields to the same conclusions as mine:
http://www.grupponamias.com/index_en.html?http://www.grupponamias.com/art_106_en.html
I also think there are many factors that play a role in achieving one result or another in cyanotype process. The sum of all of them may lead to a process that is suitable for one specific user and perhaps not for another one.

What is the cyanotype boost process

The cyanotype printing procedure I adopt is not very easy, since I’m concerned of stability. I work with a technique that, in my opinion, should give my prints a good stability over time. We may call it archival processing for cyanotypes, even if it not a common archival procedure which is used for most of the traditional photographic production. Cyanotypes must undergo a particular archival process. I will describe it further on this post.

Within the due archival procedure, I actually fine tuned the process to what I call ‘cyanotype boost process’. With my cyanotype boost process I can obtain cyanotype prints with a dark indigo look rather than cyan. The tone scale goes from a deep indigo blue to white, with a very good scale of details in between.

Such a result cannot be the product of a single factor of the process. In fact I have realized that my cyanotype technique differs from the most common processes available on online pamphlets by several factors. I am very pleased by the results I can achieve and I have decided to share with this post some hints for to help other cyanotype artists to get more extended tones and richer hues.

Six key factors for cyanotype boost process

Looking back, I have found six key factors which are responsible for such results. One single factor can help to get deeper prints than normal. But it’s the sum of the five together to boost the cyanotype print to the final results you can see on my gallery and on my Instagram profile.

They are (not in process order):

1. use hydrogen peroxide;

2. make the right negative;

3. choose the right intensification process;

4. add wetting agent to recipe;

5. choice of paper;

6. brushing technique;

In this post I will describe those six factors one at a time.

Why boosting a cyanotype?

First of all I have to admit I don’t like cyan color nor cyanotypes the most common way they are intended. My very first cyanotype prints are rooted in the last century. In the early 90’s I was playing with tonings and started doing this iron-based process to make cyan hues on silver gelatine black and white papers. The early results were technically fine, except for that cyan color which I don’t like at all.

While teaching tonings to my student classes, I stumbled on a mistake that turned to be a lucky strike for my cyan prints.

Key factor n. 1 – Hydrogen peroxide to boost oxidation

I can’t say why the students and me were playing with hydrogen peroxide. In those years we were experimenting lots of different chemicals to make weird looks to our prints, including split toning. Well, a cyanotype went in a tray were hydrogen peroxide was poured along with water, and suddenly the print turned deep blue!

I begun using this technique for all my cyan productions since then, because I liked the indigo-blue hue so produced so much. That hue was changing accordingly with the type of paper. I’ve learnt that chloride papers perform warmer blue, while iodide papers turn into the deepest blue ever seen.

The curiosity is that I believed with that mistake I discovered something new, that nobody knew before. Those were the years of the pre-Internet and the possible knowledge was only achievable reading books and talking with elder photographers. The truth was another one, yet to be realized.

I gave up with tonings experiments at the end of the century, when the only toning baths allowed in my darkroom were selenium and gold.

Sharing knowledge

Time passed by when I started making photographs with old process techniques such as wet plate collodion. On Instagram I met Jean Luc Dushime [dushimejl] with whom I established a pleasant connection and had some conversation around obtaining such a deep tone with cyanotypes.

When talking about my key factor hydrogen peroxide he told me that it was already a well know technique described on cyanotype text books also! I had to step down from my prop because, evidently, I was not the inventor of a new process… That’s the good side of social networking, where meeting people from the other side of the ocean such as Jean Luc can help fixing my vacuums.

Nevertheless my wrong believe doesn’t change the fact that hydrogen peroxide is one key factor for to obtain deeper tones and blue hue on cyanotype prints. Actually the Prussian blue is boosted via ferric ferricyanide oxidation. Hydrogen peroxide just boosts such an oxidation to the maximum level at once.

Natural air oxidation

It’s true that such an oxidation happens naturally over time. But I can wax my prints right now, after the process is ended, and consider my work finished now. Prints are ready to be shown or delivered on the very next day, instead of having to wait for who knows how many days for to get a results that’s unpredictable.

Potassium dichromate to boost blue?

I’ve never used bichromate to cyanotypes because I can obtain a good negative which is sometimes even too contrasty than normal. So, I’ve never used bichromate as some do to boost blue right during development.

The action of the bichromate in the coating is to bleach out the subtle highlights so the print must be over exposed in the UV printer for to compensate for such a loss. The counter result is that the shadows are printed for longer time hence they become darker after development.

So the bichromate bleaches ferric ferricyanide…! Why should I use it for to boost shadows putting at severe risk my highlights to be bleached out? I would like to receive your comments here if you have an experience of using potassium dichromate as a booster for blueprints. I will make further studies on this type of boosting process and then post them here.

I’m stick to hydrogen peroxide. But that’s not the only factor. I know many use hydrogen peroxide but cannot obtain a deep color as well. The lack of contrast is still a concern.

Photography means printing

The natural step beyond making tintypes and ambrotypes, for me, is printing with old printing processes, such as salted paper, cyanotype, Van Dyke brown, kallitype, carbon and so on. In my opinion, I believe photography means printing, otherwise that’s just imaging… So, the natural step beyond taking ambrotypes is making negatives for the silver and iron based old-style printing processes, nowadays called alternative processes.

A negative is not just a reversed image on glass

Digital photography doesn’t attract me at all. I hate Photoshop and the computer, in spite I was computer programmer on IBM machines in the early 80s. For two decades I fought against digital printing. I’ve always been looking for the perfect printing profile that doesn’t exist. Because as I hate computers they hate me as well.

I shoot wetplates, no digital intervention to cyanotype boost process

I’ve been working with scanners of any kind. They are useful indeed. Digitalization of analog archives is a very important step today, no one can part of. But I don’t find an interest in scanning my 35 mm format negatives for to make a 30×40 cm cyanotype print via inkjet internegative. That’s something you will never see in my production.

My “Abandoned roads” project is indeed taken on 4×5″ and 5×7″ panchromatic film that I later on reproduce on a orthochromatic film to make a larger internegative (8×10″) ready for salt paper or cyanotype printing. The reproduction is made with enlarger in my darkroom, developed and processed as any other film or black and white analog photo paper. No digital process happens in between.

That’s to say that today I shoot wet plates for obtaining both ambrotypes and negatives suitable for contact printing with old process techniques, such as cyanotype, without any digital intervention.

Wet plate collodion negative redeveloped with copper bleach and silver nitrate

Key factor n. 2 – Making a good wet plate negative

For me, the making of a good wet plate negative is another key factor for to boost cyanotypes. When I make a set, first of all I shoot an ambrotype, because I like ambrotypes as a wondering means for showing a picture. I like to frame them and eventually to sell a piece to somebody who likes old style photography.

An ambrotype is NOT a negative

Straight after I shoot a negative. The way an ambrotype is obtained is no good for to turn it as a negative. An ambrotype used as a negative might work to print it on classic silver gelatine paper. But that wasn’t an option when the ambrotype was popular, so I don’t make silver gelatine prints out of my ambrotypes (eventually not yet!).

A good wet plate negative for to print on cyanotype paper must be at least one stop darker than its ambrotype. That’s not an easy goal, because the nature of wet plate collodion is to keep it wet, while very long exposures may dry it out during exposure.

When such a negative has been obtained it must undergo an intensification process, because in spite its density it’s not yet valid for to make cyanotypes.

Key factor n.3 – Copper intensification or redevelopment for the cyanotype boost process

The choice of the right redevelopment process is another key factor for to make a good cyanotype print.

Personally I prefer to use a copper bleach based redevelopment process, because it can output consistent density and a strong contrast that is fundamental to my process.

If you want to deepen your knowledge on wetplate intensification processes, I wrote a post on this subject matter. Just click the link and see.

Copper bleach with rehalogenation can produce so much new silver oxide on the glass that it’s then turned black with an AgNO3 development solution. Such a great amount of density obliges a much longer exposure under the bromographer (UV printer). This is the key for getting deeper blue hues.

While under the UV printer, the paper gets very long exposure where the negative is transparent or just slightly textured, while it gets little exposure through the intensified areas of the image. This yields a broader tone scale with much darker shadows than usual printing.

Wet plate collodion negative just processed with copper bleach

Cyanotype solution formula

Without entering in the oxalate process, the following formula is one of the most common for making cyanotypes, and it works flawlessly for more than a century:

• part A: 10% potassium ferricyanide + wetting agent (1 drop every 10 ml)
• part B: 25% ammonium iron(III) citrate

The two solutions blended together are supposed to be used to seize the paper. The problem is that such a solution is repellent to cellulose. In other words, it doesn’t like to stick to the paper. It needs help.

Cyanotype compounds are not willing to stick to the paper

You should have noticed such a behaviour while doing your first coating passage. As soon as the solution comes in touch with the paper it looks like oleose and unwilling to spread.

Key factor n.4 – Wetting agent added to the basic formula

I’m used to add some drops of wetting agent to help such a solution to spread more easily on the paper. This way the chemical starts to soak the paper immediately when coating begins. I’ve noticed an increase in amount of chemical taken by the paper since when I adopted this additive.

That may seem a minor point, counter wise it’s a foundation step. See why with the next explanations.

Water development washes away most of the chemical

The development phase after exposure is a water development, as you know. In this phase the majority of the iron compound is washed away from the sheet. Your personal development technique plays a role during this phase, but I’ve seen that this phase has little to do with maximum density and blue hue depth. It’s more related to amount of details retained by the paper more than maximum blue possible.

Nevertheless the development phase is responsible for washing away the compounds. The fact is that the more the iron compound leaves the sheet, the less the same compound will be likely to produce a tone to help building up a full contrast grade. If the chemical leaves the sheet, that’s useless.

If you want to cast your cyanotype production to an upper level, you have to make the sensitive solution more ‘willing’ to stick to the paper. Aka, the solution should enter more deeply in the fibers.

Key factor n.5 – Choice of paper

In my experience I have seen structured papers performing better with coating than heavy pressed papers. I use Fabriano Rosaspina for years and always got very good results. Rosaspina is kind of a budget art paper from Fabriano. It doesn’t compare with more expensive papers such as Artistico by Fabriano or Cot320 by Bergger. Sometimes has issues and the production is not consistent. It’s indeed a museum quality paper, acid free, unbuffered and water-resistant for over than 24 hours if left in a bath.

On the other hand, it’s reported by Alberto Novo (see link above) that Fabriano Artistico, the high-end paper from Fabriano, is hard in contrast compared to Rosaspina. That’s not good for my negatives, maybe it’s good for yours. Arches Platine seems to perform the opposite. It should be softer.

Rosaspina’s best characteristic is in its fibers. The surface is porous and the fibers are quite loose, enough to catch the chemical and keep it stick. Bergger Cot320, on the other side, smoother, more compact, has less attitude to keep the chemical if compared to Rosaspina.

Find your own paper

The considerations on Rosaspina are pretty personal. I’m not Fabriano affiliated in any manner. Take this hint on papers just as a starting point for your personal research. I suggest to make your own tests with the papers available in your area because I understand the look of a paper may be pleasant to one photographer and ugly to another.

Consider also that a brand is not a product. I mean that within a brand there are products and products. Arches, for example, is a remarkable brand. Indeed the paper I used years ago was performing in a terrible way and I abandoned it soon. I can’t remember what type was unfortunately…

Key factor n.6 – Coating with brush

Sponge or rod coating users may find the next considerations helpful. In my opinion, if you want to get the deepest tones with cyanotype printing, there is no better way that brush coating. Let’s see why.

Along with the choice of the right paper there is the coating technique for to make the compounds more sticky to the sheet. The mechanical action of a good brush makes the chemical penetrating better into the fibers. Moreover I suggest to be ‘rude’ while brushing. Don’t be afraid of ruining the paper or to strike it. The chemical must go deep inside the fibers. The mechanical friction of the brush on the paper should achieve such a result.

I know some people just make some soft passages, for just to cover the surface of the paper. I use my brush back and forth many times, crossing the strikes more than once. That energetic action pushes the chemical deep into the paper, more than any other technique. And I coat twice.

That’s why I do not use sponge nor rod for coating my sheets. The two are too weak when it comes to mechanically pushing the chemical within the fibers of the paper.

The cyanotype boost process step by step

The full cyanotype boost process as I’m used to write down on my notes, in process order, is as follows:

1. Start with a very dense and contrasty negative, obtained with wet plate collodion photography
2. Use a strong bleach and redevelopment process, such as copper.
3. Choose a porous paper that’s willing to take ferric compounds;
4. Double coat paper using active and energetic brush strikes.
5. Add wetting agent to cyanotype solution.
6. Expose to death in the bromographer. Some of my best prints were obtained after solarization occurred!
7. Develop in strong acid water. Acid weakens prints, because it takes out the most medium details possible, that’s why it is necessary to obtain very strong prints out of the bromographer.
8. Keep rinsing with weak acid water until hydrogen peroxide bath.
9. Final rinse the papers in demineralized water. Pay attention at using tap water. In most areas of the world it’s quite alkaline. Alkali reduces ferric ferricyanide, hence bleaching out the print. Sometimes I forget my tap water is very alkaline and I wash my cyanotypes with that water. The prints get ruined in few weeks.

Here we are! That’s my recipe for the cyanotype boost process in order to obtain an extended tonal scale with very deep blue hues. I hope this essay can help you to make a step forward to deep blueprints.

Share this work

If other willing users want to share their comments along with this post they are welcome. We can all take advantage of sharing our studies to improve our blueprint process. I’d appreciate any of your feedback using the comment line herewith. Feel free to comment and share your personal process if you like. It’s always important to learn something new from other people’s experience. We all need help to improve our art.

I kindly ask you to respect my work. If you like to share this post or part of it please mention my name, link my website and/or my social profiles. I’d appreciate if you follow me on Instagram (check footer of this page). Thanks.

That’s all, folks! Happy cyanotype printing to you all.