Many know or refer to mordants as natural dye fixatives. I’m here to tell you all a secret… mordanting doesn’t have to be difficult, confusing or scary. I am going to show you how to mordant in a few easy to follow steps.
When it comes to natural dyeing, mordanting is the key to stronger, longer lasting colors. However, it should be mentioned that some plants will not make dyes that are colorfast or lightfast regardless of how well the fiber is mordanted. Plants such as beets, cabbage and berries are not good plants to use for dyeing if you’re hoping to achieve long lasting colors.
In this post, I’m going to teach you how to mordant. I will share my favorite method for mordanting cellulose fibers. It is a two step, cold morndating process that uses tannin as an assist and an aluminum salt, aluminum acetate, as the mordant.
Why Mordanting is Important and How it Works
When dyeing fiber, the goal is that the dye particles will create a strong bond with the fiber. However, dye particles will not create a strong bond with cellulose fibers on there own. They need a little help from their friends, mordants and assists.
The way to create a strong bond between fiber and dye is to soak fibers in a tannin bath before soaking them in an aluminum salt bath. The tannin bath is an important step because aluminum salts don’t readily bond to cellulose fibers but tannins will.
First, the tannins form a weak bond with the cellulose fibers then the aluminum salts bind with the tannins. When the tannin and aluminum acetate form a bond they become stable and insoluble and are fixed into your fiber.
When a mordanted piece of fiber is placed into a dye bath, the dye particles bond with the mordant creating another stable, insoluble bond between the dye and mordant.
A note before beginning
Mordanting isn’t difficult but it does take around 5 hours to complete from start to finish. You will want to choose a day where you have time to complete the entire process. It may seem appealing to soak the fibers in tannin on one day and then finish the process with the aluminum acetate soak on another day. However, because tannin only forms a weak bond with cellulose fibers, the process of re-wetting the fiber before the aluminum acetate bath may damage some of the tannin bonds.
Supplies
- Two buckets or stainless steel pots
- Tannin (I use gallnut)
- Aluminum Acetate (this is the aluminum salt)
- Scale
- Thermometer for liquids (a candy thermometer works well)
- Long handled spoon
- Small spoon
- Jar or small bowl
- Rubber Gloves
- Water
- Fiber
Note on choosing the size of the pot or bucket
You will want to choose the vessel depending on the amount of fiber you will be mordanting. Your fiber should have plenty of room to move freely. If the fiber is squished into the vessel, it is likely that you will have uneven results.
Step 1 – Preparing Fiber for Mordanting
The first step is to scour your fiber. Check out this blog post for instructions on how to scour.
If you’ve already scoured, skip ahead to step 2.
Step 2
Weigh your dried fiber to determine your weight of fiber (WOF). You may have already done this before scouring. However, if you’re going to mordant a different amount of fiber than you scoured, you will need to weigh it again to determine your new WOF.
Step 3
Wet out the fiber by placing it in water to soak. This can be done in a bowl, pot or sink.
Step 4
Measure out the amount of tannin you will be using based upon your WOF. When using gallnut, I use 10% WOF (e.g. if the WOF is 100 grams, you will need 10 grams of gallnut).
Here’s a simple formula to determine the amount of tannin to use:
WOF x .10 = amount of tannin to use
Step 5
Completely dissolve tannin in warm water. I like to dissolve the tannin in a jar with of water before adding it to the large bucket I will be mordanting in. Mixing in the jar first allows me to really be able to see if the tannin is completely dissolved.
Step 6
Fill a bucket or pot with warm water. The ideal water temperature is between 110-120 degrees F. It’s okay if the water is a bit cooler than 110 degrees F but it shouldn’t be any hotter than 120 degrees F. If the water is cooler than 110 degrees F, the fiber will need to soak for a bit longer than the recommended 2 hours.
Step 7
Add pre-dissolved tannin to the vessel of warm water and stir well to incorporate. Now you have a tannin bath that is ready for fiber!
Step 8
Wring excess water out from fiber and add damp fiber to the tannin bath. Use a spoon to push the fibers into the bath and push air bubbles out until the fiber is completely submerged.
Allow the fibers to soak for 2 hours, stirring occasionally to ensure that the tannin will be evenly bonded onto the fiber.
The tannin bath will cool to room temperature during this process. That is completely okay and to be expected.
Note on Soaking Time
I’ve experimented with soaking fibers for much longer periods of time. I used to soak my fibers in tannin for 12-24 hours. However, I began soaking them for less and less time and found that the shorter soaks were more easy to attend to and gave better (more even) results.
Step 9
After the fibers have soaked in tannin for 2 hours, remove them and squeeze the excess water back into the tannin bath before giving them a gentle rinse.
Remember that the tannin does bond with cellulose fiber but the bonds are weak. Vigorous rinsing may damage some of the bonds.
Set the fibers aside while you prepare the aluminum acetate bath.
Step 10
The process for making the aluminum acetate bath is identical to making the tannin bath. However, aluminum acetate is an extremely fine powder that isn’t safe to inhale. To avoid breathing it in, you may want to wear a mask during the measuring and mixing.
It’s also best practice to wear rubber gloves while working with aluminum acetate to avoid skin exposure.
First, measure out the aluminum acetate based on your WOF. You will need 10% WOF. Then completely dissolve the aluminum acetate in a jar of warm water (no hotter than 120 degrees F). The aluminum acetate will be lumpy but keep stirring, it will eventually dissolve.
Fill your second bucket or pot with warm water (between 110-120 degrees F) and add the dissolved aluminum acetate. Stir well to incorporate.
Now you have a aluminum acetate bath that’s ready for fiber!
Step 11
Squeeze excess water from the fiber and add them to the aluminum acetate bath. Use a spoon to push out air bubbles until the fiber is completely submerged.
Allow the fiber to soak for 1-2 hours, stirring occasionally. This bath will also drop in temperature which is perfectly okay.
Step 12
When the fiber has soaked for 1-2 hours, remove from the aluminum acetate bath and squeeze excess water back into the bath.
Now the tannin and aluminum acetate have come together and formed that stable insoluble bond that I mentioned earlier. The mordant is now fixed into your fiber! Hurray!
Step 13
Now the mordanted fibers should be rinsed thoroughly to remove any excess aluminum acetate that is not bonded.
If the excess, unbonded aluminum acetate isn’t rinsed from the fiber, it will float off when the fiber is placed into a dye bath and attach with the dye particles before the dye particles are able to attach to the mordanted fiber. This will leave less available dye particles in the dye bath.
After rinsed, the fibers can be placed in a dye bath immediately or dried and saved to dye at a later time.
For more information, please check out my self-paced online Natural Dye Course: