Tea is a straightforward way to move away from Prussian blue, because the tannin it contains reacts with the iron in the print and makes the image slide towards brown. A tea bag, hot water and a thoroughly dry print are all you need to get warm sepia tones, and that is where we recommend starting your first toning.
This page sticks to tea toning alone: its bath, its concentration and the method that leads to brown. It is part of the wider work of cyanotype toning, which reviews all the ways of changing the colour of the blue. If the process is still new to you, the complete cyanotype guide puts the starting blue, and the moment toning comes in, back into context.
What tea does to the print
Tea works through its tannin, the substance in the dried leaf that binds to the iron in the cyanotype and forms a brown compound, the same one that gives its colour to old iron gall ink (in French). The Prussian blue does not really disappear: it takes on a brown that warms it and gradually covers it, and it is this marriage of cool blue and warm tannin that produces sepia tones.
The final shade depends on the amount of tannin deposited. A light bath leaves a brown mixed with blue, soft and slightly cool, while very strong tea pushes the image towards a full reddish brown, closer to old sepia.
Choosing your tea
Only the tannin content matters. Black tea is the richest and most reliable, and it is the one we recommend for a first test, whether it is a robust Assam or a simple breakfast tea.
Green teas contain less and tone more gently, towards light, slightly yellowish browns, while rooibos leans towards reddish browns. In a workshop, a few cheap black tea bags are simply kept to hand, stronger and more consistent than fine teas.
Preparing the bath
The bath is prepared like a concentrated infusion:
- Steep three to five black tea bags in half a litre of very hot water for about ten minutes, until the liquid is dark and almost opaque.
- Remove the bags and let the bath cool until lukewarm, because boiling water would soak the paper through.
- Use a flat tray, wide enough for the sheet to lie flat and be covered in one go, with no fold that would hold the tannin unevenly.
The method step by step
Toning is done on a print that is already finished, in other words correctly exposed, rinsed in clean water until it runs clear, then completely dried. A poorly rinsed cyanotype retains residual salts that disturb the reaction, so it is better to start from a stable image whose blue you already know. How carefully you go about rinsing the cyanotype directly determines how clean the toning will be.
Lower the sheet flat into the lukewarm bath and watch the colour, because the colour is in charge, not the clock. Within a few minutes you see the blue warm up and slide towards brown, and you take the sheet out as soon as the hue you want is reached, knowing that it will look a little darker wet than dry.
Adjusting the intensity of the brown
The length of the bath sets the intensity. Two to three minutes in the bath gives a light sepia that keeps a memory of blue; a soak of ten to twenty minutes pushes towards a full, warm brown.
It is better to start short, take the sheet out to judge, and put it back in if you want to go further, because the tannin cannot be removed once fixed. Finish with a brief rinse in cold water, without rubbing, then dry flat and away from direct light while the brown stabilises.
Examining a print in beige-brown tones in a tray kept for toning. The shade depends on your tests; the image does not promise it.
Adjusting the brown hue
Three levers control the result: the starting blue, the concentration of the bath and the immersion time. A dense cyanotype tones to a deep, nuanced sepia, while a pale print quickly turns a dull brown, a reminder that toning extends the quality of an image rather than rescuing it.
You find your balance by testing on print offcuts before risking a good image. The cyanotype kit provides the two iron salts in bottles, with ten sheets of watercolour paper and two pipettes.
Tea among the other toners
Tea shares its tannin logic with coffee, which gives similar browns through the same reaction on the iron, with its own nuance. Coffee does, however, give browns that are a little redder and earthier than tea, and its own pigments can tint the whites a cream shade.
The same bath, handled differently, opens up other hues: tannin stopped earlier freezes a reddish purple still tinged with blue, whereas a much more concentrated infusion pushes the image towards an almost black brown. To explore other colour families, turmeric toning adds yellow and leads to green and gold, by a route quite different from tannin.
Any toning requires a well-built starting blue, and it is on this foundation that the tannin does its work.
Éric Marais — Photographer, author of two books on pinhole photography (published by Pearson) and creator of the Sténoflex. He has run introductory workshops in alternative photography, from pinhole to cyanotype, from the very beginning.