Mordanting: The Essential Fabric Preparation for Natural Dyeing and Eco Printing

One of the most important (and most confusing) parts of natural dyeing is mordanting. It is a process that happens before the actual dyeing, but it plays a fundamental role in determining both the resulting color and their permanence over time.

What is a mordant?

A mordant is a metal salt that forms an insoluble bond between the natural dye and the textile. It acts as a kind of bridge between the plant color and the fabric, directly affecting the fabric's ability to uptake color and withstand washing and wear. But mordants do more than simply fix color: they also influence the final shades we obtain, sometimes dramatically changing the tones produced by the same plant.

Mordants Used at Tinctorium Studio

At Tinctorium Studio, we work exclusively with mordants from two minerals: aluminium and iron. We have chosen these because, when used responsibly and at appropriate concentrations, they are compatible with the soil life in our dye garden and can be safely returned to the garden as part of the studio's water cycle.

Mordanting is essential because, without it, many natural dyes will produce little or no lasting colour on the fabric. It is also one of the most important creative tools in natural dyeing. By changing the mordant, we can obtain very different colours from the same plant material. Aluminium generally helps preserve brighter, clearer colours, like yellows and oranges while iron tends to darken and mute them, often producing beautiful greys, olive greens and navy blues.

Choosing a Mordant

For many people, mordanting is one of the most confusing aspects of learning natural dyeing. Unlike the more intuitive process of experimenting with plants and watching colours emerge, mordanting relies on chemistry and requires a more technical approach. It is important to follow specific recipes, paying attention to quantities, fabric weight, temperature and timing. Small changes can have a significant impact on the final result.

And knowing one recipe is not enough! There are dozens of different mordanting recipes depending on the type of fiber you are working with, the color you want to achieve and the materials available to you. Protein fibres such as wool and silk behave differently from cellulose fibres such as cotton and linen, and each requires its own approach. Understanding these differences is an important part of developing confidence and consistency in natural dyeing.

At Tinctorium Studio, all the Wear Tinctorium pieces are carefully mordanted before dyeing. This preparation is an essential part of our process and is one of the reasons why our colours have good resistance to washing and everyday wear. The choice of mineral is often connected to the season - alum for warmer seasons and iron for the colder, stormier months.

Pre-Mordanted Blanks

For those who prefer to concentrate on the creative side of natural dyeing, we have taken care of this technical step for you. In Blanks & Materials, all our blanks come pre-mordanted and ready to dye, including those supplied in our DIY Kits. This means you can skip the more technical and less creative preparation stage and go straight to experimenting with plants, exploring colors and discovering what natural dyeing has to offer.

Learning More About Mordanting

To get you started, I have an article on making and using your own iron water for beautiful stormy-colored prints. For the brighter yellow and orange colors with aluminum-based mordants the process is (unfortunately) a lot more complicated. Please join a Fundamentals of Eco Printing workshop or checkout our Blanks & Materials offerings where all the blanks have already been prepared with our signature aluminum acetate mordant and are ready to dye.