The Mysterious Iron Blanket

I am finally figuring it all out… well almost. When I first set my sights on the magic of Eco Printing I felt like I was trying to solve some crazy secret puzzle. Now, let me make it easier for you and answer one of those common questions; the Iron Blanket.

Those who had an idea how it all worked wanted to keep it to themselves, and I understand as it could be quite the commodity; like some magic recipe. Well, I feel like I am finally understanding what is happening in and around those bundles, but I would not call myself an expert either!

What is the Iron Blanket?

I get that question quite often. It is a carrier blanket that brings iron to the fabric that you are printing on. Carriers are pieces of cotton fabric or similar material (even paper towels) that will absorb the liquid solution that you’d like to combine into your combination of colour dyes and mordants and in this case it brings the iron component.

How to Make an Iron Blanket:

When I first started to ‘make’ my iron solution I used the method of soaking rusty stuff in water with/without vinegar. The problem was that it was really difficult to see how strong the concentration was. It was quite easy and did work once I had made some test runs. Buying iron sulphate is quite inexpensive and can be found in garden centres as well. It is much easier to gauge and measure for some consistency. Having said that though I still am not so fussy with exact measurements. Generally about 1 teaspoon per gallon of water is a good starting point. It’s as easy as just letting the fabric soak for a few minutes or longer before wringing out and using. Making sure the size ‘fits’ the project is also important.

How to Use an Iron Blanket:

In this above image the iron blanket is being layered above the leaves placed on the pre-dyed (cochineal) silk. The barrier (paper or plastic) will then be placed above or below to prevent ghosting through of the prints. But those are not steadfast rules as varying can make for some amazing results!

What does the Iron Blanket do?

After the processing of either simmering or steaming or my ‘alternate’ processing the unrolling is quite interesting… Notice the way that the leaves have very defined edges? As I understand that is from the tannins adhering to the metal ions and in this case it is the iron. Since the entire fabric on the right is not rich with iron it prints more around the edges where the iron and tannins meet and ‘have fun’.

There are usually pretty prints on both but quite different in style. Since the iron is absorbed into the ‘Blanket’ fabric those prints are usually quite dark and not as ‘outlined’ as the ‘host’ fabric. This allows that you can actually create 2 printed pieces at once.

I use old cotton bedsheets and often retire them to use for other purposes since they are so beautiful. This would be considered the same as only dipping the fabric in an iron solution to have the tannin rich leaves print.

Notice the difference?

The images above show the use of the same leaves however the centre ones were printed with the use of the Iron Blankets. I increased the concentration as some are quite boldly outlined. The outer samples were printed with the same processing however the leaves were just dipped in the iron solution (no ‘blanket’ used).

In this case the dye colour actually printed back from the main fabric to create some lovely details on the Iron Blanket. Often multiple use will also give them much depth.

So many…

After having printed so many (yes I am a bit obsessed when I am determined) I amassed so many in varying tones. That gave me the idea to use them in a quilt. I understand that iron (especially overuse) can degrade the fabric over time but I still wonder if we are talking 50 or 100 hundred years?!

Make something with the Iron Blankets!

The variety of patterns was easy to work with as the colours seem to be made to compliment each other. This Art Quilt brings nature in with the most unique fabric prints.

Some up-cycling of leather combines with more of the ‘Iron Blankets’ to make some Eco Printed Journal Covers. Once used the blankets can be washed and used again and again building up darker prints.

I hope I have the mystery for you and have opened up your world of Eco Printing! I am open to any suggestions or comments in this evolving art form.

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  1. Thank you for this really helpful description! I can’t wait to get started. Do you know how light fast the prints are using an eco printing method? I think the alum is to increase light fastness isn’t it? Is there anything else that can be done to make it more light fast so that a piece of cloth can be left out e.g as a table runner?

    1. Hmmm, table runner? Outside or just on a table? Anything that gets exposure for long times in the sun will fade. There are some mordant processes for the different fibres and also the dyes used. The iron/tannin mix does give quite a good strong print, but can also depends on the fibre content. Answers in eco printing are never simple….

      1. Thanks Barb! I was thinking of inside (too rainy here in the UK to leave fabric outside!)…. but was just thinking that something left on a table would have a lot of light on it all the time even in the house. And I wasn’t sure how light fast natural dyes might be. I’ll have to give it a go and see!

  2. Barb~ You continue to astonish and inspire me! I’m printing on quartered bed sheets to make burial shrouds. I was just figuring out the importance of iron….carrier blankets….and other embellishments when I saw your post on Pinterest. You answered several of my questions. Nice thing about my end project is that I don’t need to wash or rinse after unbundling!

    1. Wow, I am constantly amazed. Sounds like very special work. Have fun experimenting as there is so many ways to be creative in this art form! Sometimes washing will get some residual ‘dirt’ away from the nice parts of the print though and keep things from deteriorating as much!

  3. Hello Barb, I am a beginner dyer from Czechia and first of all thank you SO much for sharing all your knowledge with us! You are a neverending source of inspiration to me. I am trying the iron blanket for the first time today and I have some questions…should the target fabric and iron blanket both be previously unmordated or can I mordant any of them with alum (or pretreat with soy milk)? If they are unmordanted, will the iron be sufficient as mordant and will the print stay (on both target and blanket fabrics) or will it wash away more easily (than when mordanted with alum)? You write you reuse the blankets but I would like to use them as they are nicely printed too. Thank you a lot in advance, you are my hero <3

    1. There are many opinions on these subjects. It will also depend on the fabric/fibre choice Generally, having the proper mordant on the target fabric is best for longevity. Sometimes those who want to keep the iron blanket will post-mordant it. Some will just use the nature of an aluminum pot as a source of mordant as well. I know those are not defined answers but that is the nature of this art form, but that is also the beauty of it, never know what magic will happen.

  4. Hello barb
    I am beginner of eco printing. I got knowledge about iron blanket from your article. Thank you so much for your sharing. I will try it. 🙏🙏

  5. Do I have to mordant anew the iron blanket between each eco dye project. And how long to steam.

  6. hey Barb, thanjs fot the clear furections! question. wondering if you neutralize the rusted fiber with baking soda after printing? many thanks, pasha

  7. Your quilt is stunning!!!

    I am also a maker, and I share freely, any knowledge I have…it’s so refreshing to meet another maker, who shares so freely – bravo!

  8. Just wondering if you know of any brand names or is ferrous sulphate called something else at the garden center?
    I was at 2 different ones today and they did not know what I was talking about.

    1. I find that quite common (maybe since they don’t get much interest) and you probably need to shop at a pottery supply or printing/dye supplies place. I often get mine from amazon. Good luck!