ALUM MORDANT (Potassium Aluminum Sulphate Dodecahydrate)
~ Necessary for most plant dyes to ensure colour fastness ~

Alum is considered the safest and least harmful mordant used in natural dyeing. It helps fix dyes to fibres and enhances colour retention. What many don't realise is that Alum occurs naturally in nature, and some plants, such as Lycopodium, contain natural Alum.

Mordanting Cellulose Fibres

For mordanting cellulose fibres, please refer to our blog for detailed recipes:

• How to Mordant Linen and Cotton Fabrics Successfully – AppleOak FibreWorks

• How to Mordant Linen and Cotton Successfully Without Tannins – AppleOak FibreWorks

Basic Recipe for Wool

Ingredients:

• 10%-20% Alum (based on the Dry Weight of Fibre - D.W.F.)

• Wool (or other protein fibres)

• Water

• Optional: 5% Cream of Tartar (for hot mordanting)

Instructions:

Cold Mordanting:

1. Weigh your dry textile material.

2. Soak the dry material in water.

3. Dissolve Alum in hot water and add to a mordanting pot filled with water.

4. Add pre-soaked wool and let sit for 24-72 hours.

Hot Mordanting:

1. Dissolve Alum in hot water and add to a mordanting pot filled with water.

2. Add 5% Cream of Tartar to slow down the mordant uptake.

3. Add wool and bring to 80°C for 1 hour.

4. Let cool, then rinse and dye or dry for later use.

Alum is ideal for protein fibres like wool and silk, ensuring vibrant and lasting colour results.

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IRON MORDANT ~ Mordant, Colour Changer, increased light fastness

Iron (Ferrous Sulfate) is used alone as a mordant, influencing Colours and to increase light fastness when used in combination with other natural dyes.

Iron is best known for shifting yellows into greens, keep in mind that this is not given and doesn't work with every yellow plant dye, in which case it will be more of a brown. it is used to increase light fastness for weaker plant dyes, bu it will always sadden and/or darken the colours. 

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Basic recipe:

When adding Iron to your dye bath start of with 3% and use it at the end of your dye bath or as an after bath. Allow to oxidize for 10 min for full colour development.

*If you like your colours darker, increase the Iron amount by 1-2% at a time. 

**Leave for 10min than remove from dye bath - Iron will make wool brittle.

Sodium Acetate ~ Used to turn Ferrous Sulfate into Ferrous Acetate; used in the Mordanting Recipe for Cotton and Linen without Tannin (see below)

Sodium acetate, NaCH₃COO, also abbreviated NaOAc, is the sodium salt of acetic acid. We use Sodium Acetate to turn Iron into an easier digestible version of itself, Iron acetate. Similar to 'Iron Water' but you can control the amounts. Iron acetate is not as harsh on the fibres and can be easier digested by nature or your septic tank when turned into rust. Once made, it has no shelf life and needs to be used immediately. 

For mordanting Cellulose fibres, please choose one of the following recipes on our blog:

How to mordant linen and cotton fabrics successfully – AppleOak FibreWorks

How to mordant Linen and Cotton successfully without Tannins – AppleOak FibreWorks

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Basic recipe: 

1part Ferrous Sulfate

1part Sodium Acetate

Mix and dissolve in Water. I find that it makes the iron stronger and we only use 1% of Iron acetate on most recipes. Warm water will also intensify the reaction.

Neem Leaves and Spray

Neem Leaves

These Neem leaves are grown on a small organic farm in India. The farm is kbA registered (registered organic).

Available in leaf form or as spray*

Neem is very popular and is used for so many things, medicinal, anti-fungal and as insecticide.  We treat all our articles with the neem oil spray in order to protect the yarns and wool from moths.

Neem oil Spray 

Neem oil, cold pressed from the fruits and seeds of the Indian Neem tree. Like the Neem leaves, the oil is ideal for protecting fabric, yarn and fibers from insects and moths. I use it all the time and I have yet to see a moth!

200ml spray bottle of Neem oil contains: cold pressed Neem Oil mit 1% Azadirachitin (active ingredient in Neem oil) natural essential oils, Isopropyl - alcohol

What customers say:
"Brilliant keeps midges out too and the smell just goes away I found it quite citrus but it may smell different to each person Hubby smelled faint lemongrass"

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Basic Recipe (Leaves): 

Sew little pouches (or use drawstring bags), just like Lavender pouches, stuff them loosely with Neem leaves, and put them into your yarn/wool storage. They smell pleasantly, but that is my opinion and so far doesn't seem to leave an odor on the yarn/wool.

100gr is enough for 5 small pouches.

Basic Recipe (Spray):

Simply spray onto your items, there is no trace of the oil or long term smell on your products. Even though the oil smells strong when applied. Pleasantly though, but that is my own opinion.  

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A Modern Aluminium Mordant for Linen, Hemp & Cotton

Aluminium lactate is a highly effective mordant for natural dyeing on cellulose fibres such as linen, hemp, cotton, ramie and nettle.

Produced from lactic acid obtained through the fermentation of renewable raw materials, it offers a more sustainable alternative to aluminium acetate while producing bright, clear and colourfast results.

Fully soluble at room temperature and compliant with GOTS 6.0 standards, aluminium lactate is easy to use and suitable for both beginners and experienced natural dyers.

Product Details

Our Approach to Mordanting Cellulose Fibres

At AppleOak FibreWorks, we recommend a tannin-first approach when mordanting cellulose fibres.

Unlike wool and silk, cellulose fibres have relatively few natural binding sites for mordants. While aluminium mordants can improve dye uptake on their own, we have consistently found that a preliminary tannin treatment produces stronger and more durable results.

The tannin acts as a bridge between the fibre, the aluminium mordant and the dye, helping improve colour depth, wash fastness and long-term durability.

Step 1 – Tannin Bath

Low-colour tannins:

• Oak Gallnut
• Sumach Gallnut
• Tara Powder

For a background colour:

• Acacia Extract
• Myrobalan
• Chestnut Extract

Step 2 – Aluminium Lactate Bath

Use aluminium lactate at approximately 5–8% WOF (weight of fibre).

A Note on Dunging & Chalk Baths

Some modern recipes recommend aluminium mordants followed by bran, chalk or dunging baths.

While these methods may improve dye uptake, our own experience and understanding of the chemistry suggest they do not create the same durable tannin–aluminium complex traditionally used on cellulose fibres.

For projects where wash fastness matters, we continue to recommend tannin followed by aluminium mordanting.

Suggested Usage Rates

Traditional Recipes, AppleOak Methods & Learning Resources

Natural dyeing is full of conflicting recipes and advice. Over the years we have tested a wide range of mordanting methods on linen, hemp and cotton and shared our findings through both our blog and the AppleOak Academy.

Traditional recipes, AppleOak cellulose mordant guides and in-depth educational resources can be found here:

AppleOak Blog

https://appleoakfibreworks.com/blogs/news/tagged/how-to-mordant-linen

Join Our Free Natural Dyeing Community

Looking to deepen your natural dyeing knowledge and connect with other passionate dyers?

Start by joining our free Natural Dyers Academy community, where you'll find inspiration, discussions, resources, and opportunities to learn more about natural dyes, mordanting, fibre preparation, colour exploration, dye plant cultivation, and sustainable textile practices.

Join the free community here:

https://the-natural-dyers-academy.mn.co/share/Mz7coMI6VgbJMchB?utm_source=manual

Inside the community you'll find:

• Natural dyeing discussions and inspiration
• Helpful resources and learning opportunities
• Dye plant growing and harvesting tips
• Colour studies and recipe sharing
• Community support from fellow natural dyers
• Information about workshops, courses, and Academy membership options

If you'd like more structured learning, in-depth tutorials, workshops, and exclusive resources, you can also explore our full Natural Dyers Academy membership from within the community.

Please Note

For textile and craft use only.

Not intended for food, cosmetic or medicinal applications.

A Modern Mordant for Linen, Hemp & Cotton

Aluminium acetate is one of the most widely used mordants for natural dyeing on cellulose fibres such as linen, hemp, cotton, ramie and nettle.

Unlike alum, which works exceptionally well on protein fibres, aluminium acetate has become a popular choice for cellulose fibres because it can help produce bright, clear and colourfast shades.

Product Details

Our Approach to Mordanting Cellulose Fibres

At AppleOak FibreWorks, we use two different approaches depending on the desired result.

For Maximum Colourfastness

A tannin followed by aluminium mordant remains one of the most reliable methods for achieving durable colour on cellulose fibres.

Recommended tannins include:

• Oak Gallnut
• Sumach Gallnut
• Tara Powder

These tannins contribute very little background colour while helping create a strong bond between fibre, mordant and dye.

For projects where a slight warm tone is acceptable, the following tannins may also be used:

• Acacia Extract
• Myrobalan
• Chestnut Extract

For the Whitest Possible Background

When preserving the natural whiteness of linen or cotton is important, we recommend a tannin-free aluminium acetate method similar to the approach described in our guide:

How to Mordant Linen and Cotton Successfully Without Tannins

In this method, aluminium acetate is not used directly as a purchased mordant. Instead, a strong aluminium acetate concentrate is prepared from alum (potassium aluminium sulphate) and sodium acetate before use.

1. Scour the fibre thoroughly.
2. Prepare a concentrated aluminium acetate solution from alum and sodium acetate according to the recipe in our guide.
3. Mordant the fibre using the freshly prepared aluminium acetate solution.
4. Follow with a chalk bath (calcium carbonate) to fix excess acetate and improve mordant performance.
5. Rinse and proceed to dyeing.

This approach avoids the cream, beige or yellow cast that even low-colour tannins can introduce, making it particularly useful when dyeing pale yellows, pinks, blues and other delicate shades where a white background is desirable. However, it works best on smaller projects.

A Note on Tannins and Background Colour

Tannins can improve dye uptake and durability on cellulose fibres, but they also contribute varying degrees of colour to the fibre.

If maintaining a bright white base is the priority, a tannin-free aluminium acetate and chalk process is often the better choice.

Suggested Usage Rates

Mordanting Guides & AppleOak Methods

Detailed cellulose mordanting guides can be found here:

https://appleoakfibreworks.com/blogs/news/tagged/how-to-mordant-linen

Including:

• Tannin mordanting methods
• Tannin-free cellulose mordanting
• Aluminium acetate and chalk methods
• Approaches for preserving a white background

Join Our Free Natural Dyeing Community

Looking to deepen your natural dyeing knowledge and connect with other passionate dyers?

Start by joining our free Natural Dyers Academy community, where you'll find inspiration, discussions, resources, and opportunities to learn more about natural dyes, mordanting, fibre preparation, colour exploration, dye plant cultivation, and sustainable textile practices.

Join the free community here:

https://the-natural-dyers-academy.mn.co/share/Mz7coMI6VgbJMchB?utm_source=manual

Inside the community you'll find:

• Natural dyeing discussions and inspiration
• Helpful resources and learning opportunities
• Dye plant growing and harvesting tips
• Colour studies and recipe sharing
• Community support from fellow natural dyers
• Information about workshops, courses, and Academy membership options

If you'd like more structured learning, in-depth tutorials, workshops, and exclusive resources, you can also explore our full Natural Dyers Academy membership from within the community.

Please Note

For textile and craft use only.

Not intended for food, cosmetic or medicinal applications.