Aluminum Acetate
Note: Some dyers omit the initial tannin process when using Aluminum Acetate. In our experience we have found keeping the tannin process results in superior lightfastness.
Measure aluminum acetate at 8% WOF. Dissolve in hot water and add to the kettle.
Add wet fibre (already treated with tannin) to your kettle.
Fill the kettle with enough hot water 48°C - 60°C to cover the fibres. Stir.
Let soak for 1-2 hours (cover the kettle so it stays warm) or steep overnight.
Chalk (fix) the fibre. Aluminum acetate must be fixed prior to dyeing. In some cultures this is known as dunging (as cow dung is used, which is high in phosphates). To 5 litres of warm water add 50g of chalk (calcium carbonate). Fully wet the fibre and wring out. Rinse thoroughly after chalking. These solutions may be kept and refreshed after every 10kg of fibre.
As an alternative to chalking you may use 100g of wheat bran to 5 litres of warm water. The wheat bran needs to soak for about 30 minutes before adding your fibre. The wheat bran option is sometimes preferable for processes using thickened mordants. Rinse thoroughly afterwards.
Now the fibre may be:
Dyed immediately
Dried completely for dyeing at a later date.
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Fra (Natural Dyes)
Aluminum Acetate
Aluminum acetate is often the preferred alum mordant for cellulose fibres and fabrics. It is refined from bauxite with acetic acid as a purifying agent. Some dyes develop to a richer shade on cellulose when mordanted with aluminum acetate. Aluminum acetate is the recommended mordant when printing with natural dyes. It is more expensive and sometimes hard to find. Use at 5-8% WOF.
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Homemade Aluminum Acetate
Aluminum acetate can be made from sodium acetate and potassium aluminum sulfate. Depending on the availability of these materials in your area, this can be cost effective.
To make enough aluminum acetate to mordant 1 kilo of fabric, combine in 3 litres of hot tap water:
150 g sodium acetate or calcium acetate
150 g potassium aluminum sulfate
This can be added to your mordant bath (see the how-to section).
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Homemade Ferrous Acetate
When printing with natural dyes, we recommend changing ferrous sulphate to ferrous acetate to avoid bleeding and ferrous transfer (the migration of iron).
5 g ferrous sulfate
100 ml vinegar
3 g lime (calcium hydroxide)
Combine the below ingredients in a plastic container and stir well. If thickening is required, weigh the amount of ferrous acetate you wish to thicken and add 1% of guar gum.
Ferrous acetate needs to be fixed to the cloth. We use chalk (calcium carbonate) 50g in 5 litres of warm water. Once your goods that have been treated with ferrous acetate are fully dry, dip them into this solution. This solution may be kept and reused again and again. Generally you may refresh with 50 g of chalk after each 10 kg of fabric.
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Fra (Botanical Colors)
Mordanting with Aluminum Acetate
We often mordant cellulose (plant-based) fibers with aluminum acetate, and then follow that with a wheat bran or a calcium carbonate bath, as either of these ingredients help to improve the aluminum acetate’s performance.
Don’t have aluminum acetate? You may also successfully mordant using tannin and aluminum sulfate. This is a traditional mordant used for plant fibers prior to the introduction of aluminum acetate and is applied at room temperature. Instructions are available here and are courtesy of Catharine Ellis and Joy Boutrup’s book, The Art and Science of Natural Dyes and The Studio Formulas Set for The Art and Science of Natural Dyes (companion recipe cards to the book).
For mordanting:
100 grams cellulose fiber
5 grams (2 rounded teaspoons) of aluminum acetate
A container to dissolve the aluminum acetate
Heat source (optional; see Note)
A large stainless steel dye pot
Dye rings (if dyeing skeins of yarn)
Choose either wheat bran or calcium carbonate as your final bath. You do not need to do both.
For wheat bran bath:
The above 100 grams/4 ounces of mordanted fiber
5 grams/.17 ounces./4 teaspoons wheat bran
Cheesecloth
OR
For calcium carbonate bath:
The above 100 grams/4 ounces of mordanted fiber
5 grams/.17 ounces./1 rounded teaspoon calcium carbonate
Safety instructions
We recommend wearing a dust mask or respirator, gloves, and an apron with all powders as they can be irritating to the nose, throat, and skin. Aluminum acetate is very powdery, smells strongly of vinegar and can irritate nose and throat. We strongly recommend adult supervision if working with children and keep all mordants and dye ingredients safe from children and pets.
We also recommend that you keep dye tools and utensils separate from kitchen tools and work with plenty of ventilation. Aluminum acetate may be safely disposed in a municipal water system by pouring down the drain. Do not dispose of in waterways or drains that flow into waterways.
Calculating the amount of mordant
- Aluminum acetate: the recommended amount of aluminum acetate is 5 to 10% WOF, or 2-4 rounded teaspoons for 100 grams of fiber. A higher percentage of mordant will increase the depth of shade.
- Wheat bran: the recommended amount of wheat bran is 5% WOF, or 4 teaspoons for 100 grams of fiber.
- Calcium carbonate: the recommended amount of calcium carbonate is 5% WOF, or 1 rounded teaspoon for 100 grams of fiber.
Wet out the aluminum acetate in cold water and dissolve in boiling water. It may be a bit lumpy and sticky, but the lumps work out fairly quickly. A whisk is helpful. We recommend a dust mask when dissolving aluminum acetate as it is very powdery and the strong vinegar smell can be irritating.
Fill a dye pot with hot water from the tap – approximately 110-120°F. If you use hot tap water, you do not need a heat source as this is sufficient heat for mordanting. You may also use a clean bucket or container for mordanting with aluminum acetate.
Add the dissolved aluminum acetate and stir well. Then add the fiber to the dye pot, rotating the fibers gently. Press out air bubbles under fabric folds, or in floating yarn.
If you are heating cold water, heat only to 110°F.
Rotate goods occasionally and hold for 45 minutes.
Remove fibers from the dye pot. Rinsing is not necessary. Remove excess water and proceed to the wheat bran or the calcium carbonate bath.
Wheat bran bath
Enclose the wheat bran in a cheesecloth bundle if you don’t want bran bits all over your fibers. Soak the wheat bran bundle in a small bucket or container of water just off the boil for about 30 minutes. The solution will be milky. This solution lasts about 1-3 days. If you notice it starting to bubble or smell fermented, it’s time to make a fresh solution.
Fill a bucket that is large enough to hold your mordanted fabric with hot water from the tap – approximately 110-120°F. If you use hot tap water, you do not need a heat source as this is sufficient heat for the bran bath. Add the bran solution and the bundle of bran to the bucket. You can gently squeeze the bundle to extract more of the bran goodness.
Place the mordanted fibers into the bath for 30 minutes, rotating occasionally.
Remove the fibers from the bath. Rinse lightly before placing into the dye bath. The fibers are now ready for dyeing.
OR
Calcium carbonate bath
Mix the calcium carbonate with boiling hot water and add to a bucket or container large enough to hold your goods.
Add yarn or fiber and leave for 15-30 minutes.
Remove, rinse lightly and proceed to dyeing.
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Reusing the bath to save water and mordant
Reuse aluminum acetate baths at least twice. If you observe cloudiness or flakes floating in the bath, it is time to change it. Recharge the bath with 50% of the amount of required mordant, or 1 teaspoon per 100 grams of fiber for a 5% solution, or 2 teaspoons for a 10% solution.
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Storing mordanted fibers
You may leave the fibers in the mordant solution overnight, then extract excess water, place in the afterbath of wheat bran or calcium carbonate, rinse, and proceed to dyeing. Mordanted fibers may be stored damp in a plastic bag and refrigerated for 3-5 days and cured or aged, as this also seems to increase the depth of shade in the dyed fibers. For longer storage, mordanted fibers may be air dried and stored for future use. Label and store your mordanted fiber and keep it away from dust or dye powders, as it is vulnerable to staining.
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