How to Use Natural Mordants
One of my favorite herbal crafts is dyeing fabric, wooden beads, and more with botanical dyes. Botanical dyeing is a beautiful way to capture and show off the radiant colors of your favorite herbal allies. A key, often overlooked step of botanical dyeing is mordanting.
What is the meaning of the word “mordant”? I’m so glad you asked! “Mordanting” means using a mordant—that is, a special substance, natural or synthetic—to help dyes bind better to your dyed material. Since not all plant dyes are colorfast (meaning some will fade over time), mordanting your fabric can help preserve the dye longer. Mordanting can also make the dye colors brighter and even alter the color of the dye.
Choosing the Right Mordant
There are several different techniques you can use to mordant your fabric. These include making a dyeing bath with dyes rich in tannins, dyeing your fabric in an aluminum pot, and using soy milk to bind colors more fully. There are pros and cons to all of these methods, and I’ll outline them below in greater detail. The mordants I’ve included in this article are simple and safe, and they are not as strong as some other commercially available mordants that have more toxic ingredients.
If you’re reading this article to find the right mordant and want more clarity on how and when to use it in the dyeing process, read my guide to botanical dyeing. In this guide I walk you through step-by-step how to dye wooden beads with plant-based dyes, and you could also use this technique to dye fabric.
Method 1: Dyeing with Tannins
The easiest method is to use dyes rich in tannins. Tannins are natural compounds that help plant dyes stick and stay vibrant longer! Found in the bark, leaves, fruit, and roots of various plants, they act as a built-in mordant. Ever bitten an unripe apple and felt that dry, puckery feeling? That’s tannins at work! Ancient cultures used tannin-rich plant baths to create lasting colors on leather and cloth, and you can use the same trick to make your bead dyes more durable. Many plants naturally contain tannins, making them excellent choices for dyeing. Here are some great options:
- Tree Barks – Oak, chestnut, birch, sumac, alder
- Leaves – Walnut, sumac, oak, juniper needles
- Fruits & Skins – Pomegranate rinds, grape skins, unripe persimmons
- Nuts & Shells – Black walnut hulls, acorns
- Seeds & Pods – Acorns, oak galls, apple seeds, pomegranate seeds
- Tea & Herbs – Black tea, green tea, chamomile
Tannin-rich plants typically produce brown or yellow hues, but there are many subtle variations of tone and shade in these botanical colors—not all browns are the same! You can also layer and combine different dyes to create additional colors and unique effects.
Method 2: Dyeing with an Aluminum Pot
If you can get your hands on an aluminum pot, that’s another easy way to make your colors last. These days, you can get alum mordant as a powder, but it's even easier to just dunk your project in an aluminum pot, where the colors will catch on faster and stay longer! This works because the dyes react with the metal, enhancing their ability to adhere. You can also use other metals to achieve not only mordanting effects but also unique color variations—iron mordants darken dyes (achieving rich, dark colors), while copper gives them a yellow or green tint.
Method 3: Dyeing with Soy Milk
Soy milk is a modern, kid-friendly alternative to traditional mordants in botanical dyeing. Although it doesn’t have the long history of mordants like alum or iron and is technically not a true mordant but rather a binder, it has become popular in recent years, particularly among eco-conscious crafters. With its proteins, soy milk was historically used for stiffening fabric, but it wasn’t until the late 20th century that its ability to help plant dyes adhere to fibers like cotton and wood was recognized. Safe, easy to make, and perfect for beginners or kids, it offers a gentle, sustainable way to experiment with plant dyes.
No-Mordant Method
If you don't want to complicate things with mordant baths and binders, don't let that stop you from experimenting! Like sand mandalas in Tibetan traditions, your dyeing project can be a surprising, unpredictable journey—one that can be done, undone, and redone endlessly. Even if the colors fade, you can always reapply them and discover new, unexpected results. Embrace the journey, welcome change, and seek wonder. If you want to experiment with less colorfast dyes, go ahead and explore—they might lead to some delightful surprises along the way!
Tannin-Rich Herbs Benefits
Just as these herbs offer a beautiful dye color, many of these herbs can also offer medicinal gifts as herbal remedies. Tannins are powerful antioxidants that can help reduce oxidative damages to cells and tissues. Tannin-rich herbs tend to be astringent, which means they can help tighten and tone tissues. Some—but not all!—of the herbs noted above in the tannin-rich herbs list can be fantastic herbal allies to work with internally. These include pomegranate seeds, black tea, green tea, and chamomile. Other herbs in this list should either be avoided for internal use (e.g., apple seeds) and some should be used either under the supervision of a knowledgeable herbalist (e.g., black walnut hulls) or with knowledge of the correct preparation (e.g., acorns).
Here are some frequently asked questions about mordants and botanical dyeing…
How can I increase the color uptake and color saturation of my botanical dyeing projects?
The best way to increase the color uptake and saturation of your botanical dyeing projects is to work with mordants. All of the excellent mordant methods I mentioned above can help support color stability and brilliant colors.
How can I predict what the botanical dye will look like?
One of the best ways to gauge how your dyeing job will turn out is to create dyed samples on scrap fabric with the same fabric you’re dyeing. In the natural dyeing process, especially when working with natural fibers, natural dyeing, and ecofriendly mordants, it’s totally normal for there to be color differences or even surprises in the final color. Testing out your dyeing and getting comfortable with unexpected natural colors is all part of the fun!
What are some alternatives to metal mordants?
Some alternatives to metal mordants include dyeing with tannin-rich plants and using soy milk.
What are the most colorfast fabrics?
Natural fabrics like wool, silk, and cotton are among the most colorfast when properly dyed, thanks to their ability to bond with dyes effectively.
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