Aluminum Acetate

Aluminum acetate is a refined mordant powder that produces bright, clear colors on plant based fibers. It serves as an effective alternative to traditional tannins. Mordanting plays a key role in natural dyeing by helping dyes bond to fibers, improving both lightfastness and wash fastness. Without this bond, natural dyes tend to fade, shift color, or wash out over time.

Moreover, handle this product with care, it’s extremely fine and creates airborne dust easily. It smells like acetic acid and may irritate your respiratory system, so wear a dust mask or respirator and work in a well-ventilated space. Its astringent nature can also dry out your hands, so wear gloves to protect your skin. Always keep it out of reach of children and pets..

What is Mordanting?

Mordanting prepares fibers to accept and retain natural dyes. This step is essential except for indigo, which is a vat dye and doesn’t require a mordant. A proper mordant improves the lightfastness and wash fastness of your dyed fabric and ensures long-lasting, vibrant color.

You can mordant fibers ahead of time, dry and store them, or mordant and dye them in one session. If you mordant wool or silk with alum and let the fibers cure before dyeing, you’ll often see deeper, richer shades. If you’re just starting out, we recommend beginning with wool it’s the easiest fiber to dye.

Safety Information

• Personal Protection: Always wear a dust mask or respirator when handling aluminum acetate powder to prevent inhalation. Use gloves to protect your skin, as the substance can be a skin irritant. Work in a well-ventilated area to avoid inhaling fumes. ​

• Equipment Use: Dedicate all utensils, pots, and containers used for mordanting exclusively to dyeing processes. Do not repurpose them for food preparation. ​

• Storage: Store aluminum acetate in a cool, dry place away from light. Keep it out of reach of children and pets. ​

• Disposal: Dispose of aluminum acetate solutions by diluting them significantly and pouring them into a municipal water system. Avoid releasing them into natural waterways.

What You’ll Need

• Aluminum acetate (5–8% of the fiber’s dry weight)

• Calcium carbonate (chalk) or wheat bran

• Non-reactive containers (like stainless steel or plastic buckets)

• Measuring tools (scale, measuring cups)

• Protective gear (gloves, dust mask or respirator)

• Stirring utensil (dedicated to dyeing)

• Clean water

How to Mordant With Aluminum Acetate

Note: Some dyers skip the initial tannin treatment when using aluminum acetate, but we find that including it significantly improves lightfastness.

Weigh out aluminum acetate at 8% of the dry weight of fiber (WOF). Dissolve it in hot water and pour it into your dye kettle.

Add the wet fiber already treated with tannin into the kettle.

Fill the kettle with enough hot water (120°F to 140°F / 48°C to 60°C) to fully cover the fibers. Stir the bath well.

Let the fibers soak for 1–2 hours, keeping the kettle covered to retain warmth. For deeper absorption, allow the fibers to steep overnight.

Fix the fiber with chalk. Aluminum acetate requires fixing before dyeing. To fix with chalk, dissolve 50g of calcium carbonate (chalk) into 5 liters of warm water. Fully wet the fiber, wring it out, and submerge it in the chalk solution.

After fixing, rinse the fiber thoroughly. You can reuse the chalk solution, refreshing it after every 10kg of fiber.

Now, you can either:

• Dye the fiber immediately

• Or dry it completely for future dyeing

Storing Mordanted Fiber

Once mordanted, you can dye the fiber immediately or store it for later use. To store:

• Let the fiber soak overnight, then extract excess water.
• Store damp fiber in a sealed plastic bag in the refrigerator for 3–5 days.
• For long-term storage, let the fiber air dry completely and store it in a labeled bag.
• keep mordanted fiber clean and away from dust or dye powders, as it can stain easily before dyeing.