Introduction: Black Iron Fabric Dye

About: I'm a cosplayer who loves making everything from scratch and learning new crafting skills!

Some of my favorite cosplay inspiration, like The Witcher or Game of Thrones, does a really great job of capturing real-world historical elements in the costume design. For these projects, sometimes I want to go above and beyond and actually make my own dyes from scratch using materials that would have been available to the characters. And sometimes I just really want a color that I can't find in the store! Making your own dyes may sound intimidating at first, but it's really a simple process that you can take on with just a few basic chemicals and some kitchen supplies. In this Instructable, we'll tackle how to dye linen fibers black/grey using iron sulfate and tannic acid.

Step 1: Materials

For this project, you will need the following equipment:

  • 2 stainless steel or enamel pots, large enough to completely immerse all the fabric you want to dye in liquid
  • A food scale that can measure weight in grams
  • A long wooden spoon

Please note that your pots and spoon will no longer be food-safe after using them for dyeing. The materials we're working with today are not toxic enough to poison/burn you on contact, but you don't exactly want to go around licking them either.

You will also need the following raw materials:

  • Bleached or un-dyed linen yarn or fabric
  • Washing soda (sodium carbonate, also known as soda ash) - available at most grocery stores, be sure you buy a brand that's pure sodium carbonate with no additives/perfumes.
  • 15 grams tannic acid powder
  • 45 grams ferrous sulfate

One thing to be aware of when using natural dyes is that different fabrics react differently. We're inducing a chemical reaction to turn this fabric black, and you'll find that different textiles have different properties that affect that reaction. The results in this Instructable were obtained using linen cloth, but you could try any cellulose-based fiber (cotton for example) and expect roughly similar results. Protein-based fibers like wool or silk might work less well (or require some modifications to the procedure). I haven't tested to find out, but just be aware that if you use different fabrics, your results will be different!

Believe it or not, you probably have tannic acid and ferrous sulfate sitting in your kitchen or medicine cabinet already: tannins can be extracted from black tea, and ferrous sulfate is used in iron supplements. But these are inconvenient forms for our purposes: buy your dyeing supplies in pure form from either a lab supply company or a company that specializes in natural dye supplies.

I've provided suggested amounts of the chemicals here, but in general you will have to adjust the amount of tannic acid/ferrous sulfate depending on the amount of fabric to be dyed. The proportions I used were:

5 g tannic acid : 15 g ferrous sulfate : 100 g fabric

But there's no need to be too precise.

Step 2: Preparation and Safety

One detour for an important topic before we get to cooking: safety!

We're working with a couple of dangerous things here today:

  1. Large pots of boiling hot water
  2. Potentially toxic chemicals

Before diving into this project, please make sure that you have a safe workspace. Be sure you have pot holders on hand for safe handling of hot lids and that your wooden spoon is up to the task of safely extracting fabric from boiling water.

Additionally, we will be using two chemicals today (ferrous sulfate and tannic acid) in their raw form. Any time you prepare to work with unfamiliar chemicals, it's a good idea to make sure you know the procedures for safe handling & disposal, as well as any risks of poisoning, burning, or unexpected reactions. To obtain this information, let me introduce you to our friend, the Material Safety Data Sheet! This useful reference is easy to find online; if you're buying chemicals from a lab supply company, they should provide the MSDS for their products. The MSDS includes all the basic safety information you should be aware of (including first aid!) and I highly recommend reading it thoroughly before handling new chemicals.

In the case of the ferrous sulfate and tannic acid we're using today, they are relatively safe to handle and can be disposed of down the kitchen sink. But you don't want to ingest, inhale, or let your pets near them.

Step 3: Scouring

The first step is to prepare your textiles for dyeing via the process called "scouring". Fabric carries accumulated dirt, oils, or synthetic coatings that will prevent the dye from absorbing properly. Scouring essentially deep-cleans the textile to get all of that out.

  1. Dissolve 3 tablespoons of washing soda in a stainless steel or enamel pot with enough water to completely submerge your fabric
  2. Add your fabric and bring the water to a boil
  3. Reduce heat to maintain a simmer
  4. Simmer fabric for 2-3 hours

After 2-3 hours, turn off the heat and allow the water to cool slightly so that you can safely remove the fabric. Carefully remove your fabric (using the wooden spoon) and rinse in cold water.

Step 4: Tannic Acid Bath

Next you will steep the fabric in a tannic acid bath. You won't see a large change in color at this stage - at most your fabric will turn a pale brown, essentially equivalent to a coffee stain.

  • Using the food scale, measure out 15 g tannic acid powder
  • Fill another stainless steel/enamel pot with enough warm water to fully immerse your fabric
  • Dissolve tannic acid powder in the water
  • Place your fabric in the tannic acid solution, fully covering the fabric in liquid to ensure even absorption
  • Allow the fabric to steep for up to 1 hour

Step 5: Iron Sulfate Bath

This is the step where the magic happens! Having been pre-treated with tannic acid, your fabric will react instantly the moment it touches the ferrous sulfate, turning grey/black immediately. The longer you leave it in, the darker it will get. At this point, if you find that the resulting color isn't dark enough or if your fabric hasn't absorbed the two liquids evenly, you can alternate between the tannic acid and ferrous sulfate baths until you achieve the dye effect you want. For example, with the fabric you see in my photographs, the even grey was obtained after only one dunk in each pot, but the yarn didn't absorb the liquids evenly because of how it was wound. I simply loosened the skein a bit and repeated the dyeing procedure and eventually the color soaked evenly through.

  • Using the food scale, measure out 45 g ferrous sulfate
  • Fill another stainless steel/enamel pot with enough warm water to fully immerse your fabric
  • Dissolve ferrous sulfate in the water
  • Place your fabric in the ferrous sulfate solution. The color change is immediate and requires no more than ~5-10 min to reach its deepest saturation.
  • Remove fabric from the pot and rinse thoroughly in cold water

Step 6: Dry and Enjoy

Finally, hang your textiles out to air dry on a washing line and enjoy the product of your work. Congratulations!

A note on the end results: as you can see from my photographs, there is quite a wide range of colors you can end up with even following the exact same procedure. I dyed all 3 of the textiles you see here in the same pots, and as you can see the resulting colors range from nearly black in the case of the yarn, to different shades of slate grey in the case of the two different linen fabrics. Variation is to be expected with home-made dyes, but that's all just part of the fun. So get out there and enjoy your new-found home chemistry skills!