How to: Creative Use of Iron Blankets for Eco Printing

Since I love printing with botanicals so much I’m excited to introduce this how to; Creative use of Iron Blankets for Eco Printing. This is a captivating art form that combines nature, creativity, and sustainable practices to magically transfer unique pigments & motifs from leaves and botanicals onto fabric.

Understanding Iron Blankets:

Years ago I painstakingly figured out the mystery of what is called; ‘the Iron blanket. They are made by soaking (or dipping) natural fabrics in a solution containing iron which introduces iron compounds into the eco printing process. When these iron-treated fabrics come into contact with tannin-rich leaves and other plant materials, a chemical reaction occurs, resulting in dramatic colour shifts and darkening of the prints. I soon fell in love with this technique; allowing some amazing creative possibilities when thinking outside the usual technique.

If you are confused, think of it this way; special fabric shapes or motifs can be prepared to act similarly to the way leaves do and create a unique print.

Materials Needed:

  1. Iron blankets (fabric treated with iron compounds/ferrous sulfate)
  2. Fabric to print on (target fabric)
  3. Interesting ‘carrier’ fabric (weaves, laces, threads)
  4. Leaves, flowers, and botanicals for printing
  5. Tannin Solution (Myrobalan, teas or other tannins )
  6. String or fabric ties
  7. Dowel/pole to roll on
  8. Large pot or other method to heat process
  9. Heat-resistant gloves or oven mitts


1. Prepare & Choose your fabric:

In the world Eco printing basics it is understood that natural fabrics print the best. Not all types will print the same, as some benefit from more preparation such as mordanting. Cellulose fibres (cotton, hemp, linen, rayon, ramie, sisal) & Protein fibres (silk, wool, alpaca, angora)

Before printing make sure your piece of fabric is very clean. Scour (deep clean) your fabric well and consider a mordant if preferred.

2. Prepare your tannin:

There are a few options of tannins to use for eco printing purposes. Myrobalan (Harde Powder) is one of my favourites. You can also use some teas. Also there is oak galls, tara, sumac, myrobalan, pomegranate, green tea, quebracho, cutch, Black tea, chestnut bark, walnut husk, & eucalyptus bark.

The achievable prints will depend on a few factors. The absorbency of the particular fabric and the strength of the tannin solution both play factors. The weight of the carrier cloth will dictate how much pigment it can hold as well.

After soaking your unique shapes or weaves (preferably natural materials) in the tannin do blot them on a rag so that they so not drip onto your target fabric.

3. Plan your use of Iron Blanket Shapes:

Using an iron blanket often gives prints with a lovely definition around the leaf shape since it reacts with the tannins in the leaves (see examples in this post). The clearer prints come from that definition. For that reason I like to use an iron blanket as well as having some iron in the target fabric (the tannin in the leaves and shapes react with the iron) but is not always necessary.

If you don’t have prepared iron blankets, you can create them by soaking natural fabrics (cotton or linen) in a solution of iron water. To make iron water, soak rusty nails or steel wool in water for a few days until it develops a rusty appearance. Strain out any solid particles before using. You can also use prepared iron sulphate to conveniently make the solution. Do remember; a little goes a long way.

Testing & experimenting will help you develop your own recipe and concentration of the iron solution. 15 grams in a bucket of warm to hot warm will mordant about 100 grams of fabric; WOF (weight of fibre)

Since this technique depends on the combination/reaction of tannin with iron it can be in the target (fabric where prints are desired) or the carrier (the cloth that has the solution in it). Since the leaves also bring tannin I often choose to dip the target fabric in a weak iron solution as well. To see the different outcomes of methods see here. When in doubt, it is best if you make a few tests. It is such a magical art form to experiment with.

4. Arrange Botanicals on Fabric:

Lay out your damp Iron-prepared target fabric on a flat surface. Arrange the chosen leaves, flowers, and botanicals on the fabric, considering the placement and patterns you want to achieve. The underside of the leaves tends to allow better release of tannins for the prints than the top of the leaves.

Not all leaves will print, but there are some that are quite reliable like: Sumac, Silver maple leaves, cotinus, blackberry, rose leaves, walnut leaves, geranium, eucalyptus etc. Since many factors can affect the print it is best to experiment with what is available to you. Dry leaves can be stored for later use.

This is a large weave cotton mesh (soaked in myrobalan) that creates much interesting texture. It is layered over the (iron solution dipped) target piece of fabric.

5. Layer with Iron-Blanket Fabric:

Place the iron-blanket treated fabric (shapes or interesting weave) over the botanicals. This is where the chemical reaction will occur.

6. Secure the Bundle:

Carefully fold or roll the layered fabrics into a bundle. To prevent bleed-through I use a barrier layer of reused plastic. You can also use fabric, or paper. Roll the bundle as flat and tightly as possible. Secure the bundle tightly with string or fabric ties. The tightness of the bundle affects the final print, so experiment with different wrapping techniques. I like to use this technique to quickly tie it up.

7. Heat process the Bundle:

There are a few options of methods to provide the heat. Bundles can be steamed, boiled or in my case I like the ease of using the microwave.

Place the secured bundle in a large pot. Add enough water to cover the bundle or raise it above the water to steam.

Bring the water to a simmer and maintain this temperature for approximately 1-2 hours. The heat activates the chemical reaction between the tannins from the plant materials and the iron from the iron blanket.

If using the microwave make sure to not overcook, instead use the insulation under blankets to maintain heat until it cools.

8. Cool and Unwrap:

If simmering, allow the bundle to cool before unwrapping. This cooling period is essential for the chemical reactions to fully develop.

9. Rinse and Dry:

After unrolling and removing the plant material gently rinse the fabric under cool water to remove excess dye. Allow the fabric to air dry.


  • Experiment with Different Iron Treatments: Try using various iron-treated fabrics to see how different iron concentrations and treatments influence the final prints.
  • Combine with Other Mordants: Experiment with combining iron blankets with other mordants like alum to achieve a broader range of colours and effects.
  • Document Your Process: Keep detailed notes on your iron blanket experiments, including the type of iron treatment used, the botanicals, and any additional mordants. This documentation will serve as a valuable reference for future projects.

Such a magic process!

How amazing is that?! Using iron blankets in eco printing adds a layer of alchemy to the process, creating prints that are not only visually stunning but also carry the unique signature of chemical reactions between iron and tannins. As you delve into this eco printing technique, let your creativity flow, embrace the unpredictability, and watch as your fabric transforms into a canvas of intricate, nature-inspired artistry. Remember to have patience and embrace the unpredictability… Happy eco printing!

Be sure to check out all the other resources of Eco printing.

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  1. Thanks Barb! Can this process be used for paper as well? I’m not into fabrics and don’t sew but love paper ecoprints.

    1. I bet it can, as paper is essentially a cellulose fibre. It sounds like there could be a lot of possibilities with layering. Myself, I have a lot of fabric to use! Let me know how it goes!

      1. I will share my experiments here when I have a chance-I usually ecoprint in the fall when leaf tannins are highest. Thanks Barb for all your creative ideas. I think your wall paintings are brilliant!

  2. I love how that turned out! If I understand correctly, the layers are iron dipped target fabric, leaves&tannin dipped carrier fabric, iron blanket, and then plastic barrier?