7 Different Tannins and Ferrous Sulfate in Eco Printing.

Updated: Oct 20

In a previous blog I described my journey in ink making. Ink making is all about the connection of tannin rich materials with iron and a thickener, and it felt like the right time to further discover the different combinations of iron and tannins and what this means in eco printing. This blog does not describe the workings of an 'iron blanket' or ferrous sulfate carrier, you can find information about that here.


This blog is meant to show different options when working with eco printing, and hopes to inspire you to do your own research and experiments.

A small recap, tannins are divided in three major groups;


1 - Gallic tannins. Clear tannins that do not add much colour to the fabric such as tara, oak galls, oak bark, sumac (leaves and galls).


2 - Ellagic tannins. Tannins with a lot of flavonoids that will add a yellow colour to the fabric such as myrobalan, pomegranate and henna.


3 - Catechic tannins. Condensed tannins that will add brown and reddish hues to the fabric such as black tea, cutch, quebracho and chestnut bark.


For my samples I used handspun and -woven Matka silk. My favourite fabric with a lovely hand. What these wild silks have in common is that they have not been de-gummed which keeps them matte with the protein sericin layer still intact around each fiber. This makes it very easy to dye and eco print and gives more saturated colours than a de-gummed silk such as habotai would.


The samples were dyed with tannin as follows;


sample 1: 20% pomegranate powder

sample 2: 20% oak gall (European source)

sample 3: 20% tara powder

sample 4: 20% myrobalan extract

sample 5: 20% cutch extract

sample 6: 20% oak gall (Aleppo)

sample 7: 15% quebracho extract


All the samples were kept in a jar, initial bath made with hot water to dissolve the powders well, then left overnight. Stirred every few hours.



I used two different types of oak galls to understand if there is a big difference between the two batches I had from different suppliers)


Then I divided these samples for two tests. The first test was to simple divide a piece in two, and dip one half in water mixed with around 2% of ferrous sulfate. This way we can understand what the reaction is between the different tannin groups and ferrous sulfate.



The gallic tannins (sample 2, 3 and 6) do not add a lot of colour to the fabric, but together with ferrous sulfate give a reaction that leans to a deep aubergine black hue. Tara is about as strong as Aleppo galls, the European galls seem to contain slightly less tannins, we can derive this from the intensity of the reaction with the ferrous sulfate.


The ellagic tannins from pomegranate and myrobalan give us golden yellows and the extract of myrobalan leans towards a greenish yellow. With ferrous sulfate they give black with green undertones.


The red, condensed tannins from cutch and quebracho give both reddish browns, with the quebracho being much redder in shade. When dipped in the ferrous sulfate water the samples changed immediately to a deep grey.



For the next test I had one long piece of matka silk that was mordanted with 0.5 %WOF ferrous sulfate. I was laid on the work suface and the entire piece was then covered with sumac leaves, the earth side of the leaves facing down. This piece was then covered with the different pieces of tannin dyed materials in the order 1-7, covered with a barrier of brown paper to prevent ghost prints. It was further rolled very tight, and wrapped in cotton strips to keep everything neat and tight and then steamed for 90 minutes in my big fabric steamer.

After washing and drying I cut the target piece in sections for easier photography.


The ferrous sulfate rich target pieces;


The tannin rich ‘blankets’ or carrier cloths;

You can easily see how the use of different tannins not only changes the colour of your piece, but also influences the clarity of the leaf print.


1 pomegranate powder 2 oak gall (European source) 3 tara powder 4 myrobalan extract 5 cutch extract 6 oak gall (Aleppo) 7 quebracho extract


The next step is to do this test again, and now to use different leaves to see how the acidity of the leaf influences the results.


Are you just starting out with eco printing? This PDF will be a great guide to get the basics going, learn all about the best leaves, mordanting and different fabrics.


Tip; there is now a search bar in the bottom of each page, you can use it to find key words that will lead you to products and appropriate blog posts.


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