How to: Tone Cyanotypes with natural Tannins

Simply creating beautiful blue Cyanotypes with this photographic technique doesn’t end there. As you know, I love to use nature to print; (shown in my many versions of Eco Printing) so I am testing some of my tannins. Here we go; lets see how we can bring some of that magic into toning Cyanotype prints.

Cyanotypes are known for their classic Prussian blue hue, but did you know you can transform these prints into a range of warm, earthy tones? By harnessing the power of natural tannins, you can create unique and sustainable artwork. This tutorial guide will walk you through the process of toning your cyanotypes using readily available materials.

Making the Cyanotype Prints:

Summer sun and plant material just beg for some beautiful prints. The simple Cyanotype chemistry; Potassium Ferricyanide, and Ferric Ammonium Citrate chemicals mix easily.

Cyanotype Recipe:

Paint (brush or dip) the cyanotype solution to coat paper (or fabric) that will withstand washing and rinsing, such as watercolour paper. Allow to dry in a dark location. Once dry, store in a light-proof bag/box until use.

Fresh plant material or dried & pressed specimens can be used. Tip; if it is very hot weather the fresh plants may start to ‘sweat’ when exposed to sunlight under the glass. Pressing and drying will allow easier placing and more defined prints (see post here)

Exposure of your ‘Blue’ Prints:

Just like photography, the areas that are exposed will turn more blue and then greyish. Test different sunlight exposure times but realize they will turn stronger blue during the washing and developing. Alternate exposing can be made with the use of a UV light. The areas that are completely blocked will be the white highlights. Using semi-transparent materials allows mid-tones to develop. Remove the plant material and wash promptly to remove any unexposed emulsion.

Once there is no more yellow water rinsing out the final print it is ready. It will develop into a stronger blue over the next day or can be accelerated with a dip in water that has a few drops of Hydrogen Peroxide added. Let the prints dry or tone right away.

What are Tannins?

Tannins are naturally occurring substances found in many plants (leaves & nuts), including tea, coffee, and wine. They react with iron salts in the cyanotype process, altering the colour of the print. Eco Printing utilizes much of the same principles. The strength of the tannin and the toning time will determine the final colour as well as the type of plant material.

I am testing a few readily available tannins like coffee and tea as well as some favourites found in eco printing.

What is Myrobalan?

Myrobalan is the dried fruits of several East Indian trees belonging to the genus Terminalia. These trees are native to South Asia and are known for their high tannin content. Terminalia chebula is often used in traditional Indian medicine, as a tanning agent and as an aid in mordanting for natural dyeing.

Acorn Tannin:

Last fall, I found a great source of acorns; Pedunculate Oak or English oak. I had planned to use them for Eco printing but I am curious how much tannin they have. Aren’t they pretty?!

To process the tannins from the lovely nuts I slowly soaked and simmered the cracked nuts until it was a rich brew. It is difficult to measure potency so testing and observing is the best way.

Maple Leaf Tannins:

In fall here in Canada I have found some amazing maple leaves that print such amazing colour. A mix of dark red and golden tones are sure to hold a reliable amount of tannins.

Just like tea, these dried leaves are slowly heated and soaked to bring out as much printing power as possible. Generally over heating is often not the best for natural dyes, so ‘low and slow’ is my choice.

Tannins are also found in Red wine so that is another simple tannin source to explore. Tannic acid powder can be obtained at wine-making stores as well.

How to start testing:

Make sure to have a fully developed cyanotype that has been washed and dried. It should be the typical strong Prussian blue colour.

I need to keep track of the swatches so I used a simple numbering system.

The Tannin Line-up:

(From left to right)

• Strong Instant Coffee (about 2 tbsp in 500ml)
• Black Tea (8 bags in 500ml)
• Myrobalan (2 tbsp in 500ml)
• Acorn tea/dye (simmered cracked acorns)
• Fall Red Maple Leaves (simmered & steeped)
• Red Wine tannin (regular boxed version)

Have trays of clean water available for rinsing as well.

How to ‘Bleach’ a Cyanotype:

To remove the blue portion of the cyanotype print you will need to make a solution of Soda Ash (Sodium Carbonate Na2CO3) also called washing soda and water. I prefer to use this as a toner as it is readily available in the laundry aisle (Arm & Hammer Washing Soda) rather than chlorine bleach or ammonia. The strong alkali is the bleaching factor. Sodium bicarbonate (baking soda) is not the same thing. The concentration is variable for how fast the bleaching occurs. I used about 1 tsp of Soda Ash per cup (250 ml) in a flat tray.

The blue starts to disappear pretty quickly.

Step #1; Bleach Print

The bleach bath (Solution Carbonate solution) destroys the blue pigment by dissolving away the ferrocyanide ion, leaving behind a pale yellow image made of ferric hydroxide. Prussian blue pigment is rather stable in neutral or acidic environments, but it is quickly decomposed (hydrolyzed) by the presence of alkaline materials (ammonia, sodium carbonate) forming iron (III) hydroxide. For further variations I can imagine that partial bleaching allows even more interesting results.

Step #2: Rinse

The blue is gone but I’m excited to see how this remaining yellow/orange will behave with the tannins. Make sure to rinse away any of the bleaching agent in water.

Step #3: Into Tannin or dye

The first bleaching steps are the same for all tannins. The next step is the same for all the tannins. Place the strip into the tannin making sure to watch carefully. The reaction of the leftover iron with the tannins starts immediately. This is much like what happens in the world of Eco printing where the details of the leaves print when using iron as a mordant.

Each of the tannins give a different colour toning. Some teas tend to be more of a warm colour and other tannin has a somewhat purple shift. Tannins and tannic acid are found in many natural found specimens. Oak galls, (gallic acid) tree bark, leaves, seeds, cones or even wood. Some have more colour intensity than others which is the magic I enjoy!

Step #4: Various Combinations

Once the observations are made slight changes to the steps will give more options of colour shifts. Also take note of how much the contrast may change if the tannin stains the highlights of the print. Allowing some of the original blue to remain will also add some more dimension to the colour result.

One of my favourite tannins to use is Myrobalan in Eco printing!

Again, it does not disappoint as it gives a quick result and strong purplish toned cyanotype.

#1 Results:

Each test strip is completely bleached, rinsed and then toned in each tannin.

#2 Results:

Test strips are toned with no bleaching first.

#3 Results:

Test strips are only bleached partially and then toned in the tannins.

#4 Results:

Test strips are bleached, rinsed and toned twice.

Cotton Fabric Print Toning Test:

These cotton fabric swatches were completely bleached before toning. Fabric has more challenges as it tends to be more absorbent that paper which can result in more staining of the white areas of the print taking away some of the contrast with the shades of the image.

Side-by-side Comparison:

I am excited to further my ‘play’ with toning! The real tests will be when prints have a variety of blues to tone. Be aware that not all papers or fabric will ‘hold’ the colours the same way. Wetting the prints before the toning may also have some effect of the toning and absorption aspect.

Splitting a well developed print (from last year) has some interesting tones. This is a heavier weight watercolour paper.

Using my 4 favourite Tannins:

• Strong Instant Coffee (about 2 tbsp in 500ml)
• Myrobalan (2 tbsp in 500ml)
• Acorn tea/dye (simmered cracked acorns)
• Fall Red Maple Leaves (simmered & steeped)

Colour preference is a person thing… The results all show some definite shift towards warm tones but there is still much difference between them! Decisions are always difficult…

Conclusion:

I am pleasantly surprised at how easy and quick toning Cyanotype prints is! This gives me a good starting point and makes me think of ways to add even more variation to the results. I like the more neutral tones that the coffee and Myrobalan give but I also realize that leaving more blue may be another way to add more strength in the shadows. Artists and photographers always like to create alternative processes as thats what creativity is all about! I hope I’ve given you some new insights with this step-by-step; how has your Cyanotype toning gone?

The next step in my Cyanotype journey is to make some printed digital negatives; then there will be even more opportunity of toning! Come along for the ride!

If you want to start making Prints on paper or on fabric I can help!