iron mordant

iron mordant or iron water, or more precisely iron(II) acetate, is a very versatile and easy to make substance to use in dyeing and woodworking. it reacts with tannin-rich wood and turns it darker. for fabric and thread dyeing it turns dyes into a greenish direction or makes dyes darker and more dull. with some dyes, like avocado, it creates a different colour even. it’s a pretty fascinating and useful thing to have.

here’s how to make your own iron mordant:

you need:
– some scrap iron (rusty nails, steel wire, washers, etc…); i often pick up small rusty things whenever i find them, especially aras near construction sites often have little bits of rusty iron lying around. or when you’re out litter picking, keep anything rusty. steel wool works as well, if you can’t get hold of rusty stuff.
– vinegar or vinegar essence
– water
– two glass jars

put your rusty bits and pieces into the jar and cover with vinegar. if you work with vinegar essence, dilute first in order to get to a concetration of vinegar. follow the instruction on the bottle lable to do that; the vinegar essence we ususally have in supermarkets here needs to be diluted in a 1:4 ratio (1 part essence, 4 parts water).

cover with a lid, but don’t screw on tightly!!! the chemical reaction between acetic acid and rusty iron produces hydrogen. the amounts are small and safe to just dissolve in the air, but it needs to be able to escape the jar. a tight lid might have pressure adding up inside the jar and make it explode – you don’t want that!!! just remember – loose lid, and it’s a perfectly safe thing to make at home.

after one day, pour your solution into the second jar, leaving the rusty bits exposed to air; best to put no lid on. on the next day, pour your solution back on the rusty parts. alternate every day between having the rusty iron exposed to air and covered in liquid.

the liquid should turn a lovely rusty colour quite soon, a sign that it’s ready to use.

if you use it for woodworking, it’s good to go directly from the jar. if you use it for mordanting textile fibers, you need to dilute it with water, in a ratio of 1:2 (1 part iron mordant solution, 2 parts water).

or, leave it as is and only add a small amount to your dye if you want to modify your dye. this works well with avocado. iron mordant turns the pink shades of avocado into a lovely purple. to do this, you would use your avocado dye process, take out your dyed fiber, add iron solution to your dye pot (you should see the colour change immediately), stir and add the dyed fiber back into the pot and let it sit until the colour looks like you want it to.

here is an example of iron mordant solution on oak wood (also notice the bristles of the brush; they are animal fiber and also react with the solution):

iron solution on an oak wood frame:

photo (c) harald oesterle
photo (c) harald oesterle

iron solution on oak wood frame (hand plained and brushed, treated with iron mordant solution, finished with danish oil; made by @orcoyoyo):

and here is an example of avocado dyed thread and fabric, the pink ones are avocado only, the purple ones were modified with iron(II) acetate:

there are so many more variations with different plant dyes and iron mordant solution, and i’ll keep exploring and experimenting.

dyeing with onion skins

what you will need:
– onion skins (i used yellow ones here, but of course red ones or a mix of red and brown work just fine); i ususally collect all onion skins when cooking and store them in a paper bag. only use the dry, yellow/red parts, no fleshy bits, as they would start to rot and smell.
– a cooking pot large enough to hold your fabric or thread to be able to move around freely
– a colander or strainer of some sorts to strain off the onion skins once the dye has been extracted
– a muslin cloth or any other cloth to strain out fine particles – a tea towel works fine. just make sure it’s okay to dye/discolour that piece of fabric.
– wooden spoon or something else to stir – may also discolour in the process
– gloves – not really necessary; but if you want to make 100% sure not any tiny bit of yellowish colour stays on your skin, use gloves. i never do with onion dye, though.
– fabric or thread for dyeing (any animal fiber or natural fiber will work; i usually dye cotton or linen or a cotton/linen mix and don’t have much experience with animal fiber like wool and silk; they take colour beautifully, though). in this example i’m dyeing cotton embroidery thread.

to prepare beforehand – scouring your fabric/thread (speaking about cotton and linen here, this guide is not for silk or wool!!!)
in order to prepare the fiber to take up the dye as best as possible, you need to remove all possible dirt, dust, grease, … even newly bought fabric or thread has residue from spinning and weaving that you need to remove.
for fabric, wash accordingly, and then there are two options:
– either machine wash at 95° celsius with baking soda
– or (especially small pieces or small amounts) put in a pot with water and baking soda and bring to a boil, then simmer for appr. one hour. strain off the water (you will now see how much residue will have come out by the colour of the water) and rinse thoroughly until the water runs clear.

for scouring thread i always use the “simmer in a pot” method. roll the thread into a loose loop and secure it losely so it doesn’t fall apart and tangles up. tie up in one or more places, but keep it lose enough, so you don’t accidentally create a part that can’t take up the dye (this would be called a resist dye technique, which in case you want to create unevenly dyed thread is a nice technique; just don’t do this by accident). when stirring, do so very gently and try not to tangle up the thread too much.

if you dry your material after scouring and before dyeing, make sure to pre-wet it before it goes into the dye pot.

extracting the dye:
put all the collected onion skins into your pot and cover with water.

put the pot on the stove and bring the water to a boil. once it has heated up, keep it simmering for at least half an hour. depending on what you want to achieve, use more or less onion skins and let it simmer a bit longer or shorter. the more skins, the more intense your dye will get. keeping the heat below a boil will bring out more of the yellow tones, boiling it will shift the colour more towards orange/rust in brown onion skins. you’ll see the colour of your dye bath change pretty quickly, the skins give off colour quite easily.

once you have extracted the dye, strain off the skins by using a colander/sieve/strainer lined with muslin cloth. make sure to squeeze out all the dye still left in the skins. pour your dye back into the pot.

dyeing:
now you’re ready to dye your fabric or thread. for dyeing with onion skin you don’t need to mordant your fabric beforehand, which makes it really easy and quick. take your previously scoured fabric or thread (make sure it’s wet before it goes into the dye pot – soaking longer is better, wetting it quickly is better than dry) and put it into the dye. now start heating the dye up and bring it to a simmer. let it simmer for half an hour or hour – check the colour of your fabric or thread. stir gently to move the material around so the dye can spread more evenly. you can let the material sit in the dye bath over night after it has cooled down. or take it out earlier, if you like the colour. just take into account that the colour looks more intense when it’s still wet and not yet rinsed. once you like the colour, take out your material and wring it out. hang to dry. i usually wait a few days up to two weeks before i rinse out excess dye. it helps the dye stick to the fiber a bit better. but if you’re too curious to wait, rinse right away until the water runs clear and hang up to dry.

you can use the dye bath more than once, until you have used up all colour. if i want to re-use it, but not right away, i pour it into strage jars with a screw lid when it’s still hot (put a wet towel under the glass container, so they don’t break from the heat; and best put them into your sink when pouring, so even if they break you don’t mess up your whole kitchen), screw the lid on and the jars will seal themselves shut when cooling down. this way you can store your dye for a few weeks before re-using.

here is a skein of onion dyed embroidery thread – already dried, but not yet rinsed. look at those wonderful orange-red-rusty tones!

it is a very straightforward dye made out of food waste, so give it a go – it’s fun and really easy. the tones you get are always beautiful.

i’m happy to answer questions, just leave me a message right here. and also do let me know if you tried out dyeing with onion skins, i’d be happy to see your results!