Dyeing with fungi: colour begins before the pot

A fungus on cloth can give yellow, rusty orange, green, violet, pink or a shade that cannot be named accurately before the sample dries. There is no simple dictionary of "one species, one colour", however. The result depends on the age of the fruiting body, the substrate, the ratio of material to fibre, the extraction time, temperature, the pH of the water and the mordant used. Dyeing with fungi combines recognition of an organism, the chemistry of a solution and textile craft.

One of the best known species is Phaeolus schweinitzii, called in English the dyer's polypore. Young margins and older parts of a fruiting body can give different shades. Depending on the mordant, yellows, muted greens and browns appear. The common name does not mean that every specimen will behave identically. Material growing on a different host, or collected after rain, may have a different pigment content.

A traditional workshop begins with the fibre. Wool and silk are protein fibres, so they bind some dyes differently from cotton or linen, which are built mainly of cellulose. The same bath can only be compared when samples have similar mass and preparation. Residues of grease, detergent and earlier treatment all affect how colour takes. A well-run sample book describes the fibre as precisely as the fungus.

A mordant creates a link between dye and fibre, or changes the availability of a compound. Alum is a common choice for wool, and iron salts darken and shift colours, though they can also weaken the material. Copper and chromium appear in older recipes, but their use carries risks to health and the environment. The phrase "natural dye" does not make the whole process automatically non-toxic. What counts is the full chemistry of the bath and how it is disposed of.

pH acts as another variable. A small addition of acid or alkali can transform a solution, because pigments exist in different chemical forms. An experiment should use pH strips and small samples, not a random quantity of vinegar or soda. A change visible in the pot will not always survive rinsing. The final colour is judged only after drying, and its durability after further tests of light and washing.

Studies of dyeing wool with fungal extracts measure colour numerically and test resistance to light, rubbing and washing. Such a paper does not turn a craft into an industrial instruction. It does make it possible to separate a photographic effect from a practical one: a sample may be intense straight out of the bath and then fade quickly. In a textile product, repeatability and durability matter as much as an attractive first shade.

Documentation matters particularly, because recipes circulate as photographs without a method. A useful record contains the species name and who identified it, the mass of dry or fresh material, the host tree, the mass of fibre, the type of mordant, pH, temperature, time and a photograph taken under constant light. A sample number allows the result to be compared six months later. Without that, a success cannot be repeated and a failure teaches nothing.

Identifying the species is a matter of safety and of credibility. A dye pot must not go back to preparing food, and materials and mordants are not kept in food containers. Ventilation, gloves and separate tools are part of the process. Do not taste the liquor, and do not assume boiling neutralises toxins. In a workshop the issue is not edibility but contact with a concentrated extract and with chemicals.

Collecting raises an ethical question. Some of the brackets used are common and perennial; other sites are small or lie in protected areas. The North American Mycological Association's guidance encourages learning and sampling, but does not confer a right to take material. Before collecting, check the owner, the regulations and the status of the species. It is worth using fruiting bodies that have already fallen, material from lawful tree work, or a small part of an abundant site.

Not every fruiting body should end up in the pot. One mature specimen may be needed for documenting occurrence, for education or for dispersing spores. With a rare species the value lies in the observation, not the colour. A maker should record the decision not to collect as well. That is the opposite of an approach in which an online list of "the best dyeing mushrooms" becomes a map for exploitation.

Dyeing can support field knowledge. To obtain a repeatable result you have to learn the hosts, the stages of development and the variability of a fruiting body. A craft community builds comparative sample books that document not only colour but also local names and the availability of material. Such a sample book is not a formal herbarium, because the fungus has been processed, but it can draw attention to a change in occurrence and to the need for a proper reference specimen.

The slogan "a sustainable alternative to synthetic dyes" needs an accounting. Small-scale use of local, waste material may make sense. Industrial production would need steady supply, energy for extraction, water, mordants, effluent control and demonstrable durability. Collecting wild fruiting bodies on a mass scale quickly stops being sustainable. Cultures of mycelium and pigments produced by controlled fermentation are promising, because they separate production from pressure on wild sites.

The best first project is a small one. A few labelled wool samples, one lawfully obtained species, a mild mordant, a record of pH and a control sample teach more than a large pot without notes. After drying, part of the yarn can be kept in the dark and part exposed to light. Comparison after some weeks shows whether the colour is a usable material or a short-lived effect.

In this craft the aesthetics arise from constraints. Colour is not a hidden "fungal ink" that merely needs rinsing out. It is the result of a meeting between organism, fibre and process. Awareness of that dependence guards against three errors at once: a wrong identification, dangerous chemistry, and a promise of sustainability made without checking the full cost.

A cultured pigment is still far from a safe dye

Hernández and colleagues did not boil foraged fruit bodies. They cultured five ascomycete isolates obtained from rotten wood under controlled conditions, producing extracellular pigments at 0.10–0.28 g/L. Red pigment from Talaromyces australis and yellow pigment from Penicillium murcianum were selected for wool trials, each used at 0.1 g/L. After one accelerated wash cycle—15 minutes at 60°C with detergent—the authors judged the colour performance acceptable without a mordant or fixing agent. This is promising laboratory evidence, not a domestic dyeing recipe or a sustainability assessment. The paper explicitly calls for toxicity testing and chemical-structure identification before application. Its result cannot safely be generalised to wild species, skin contact, wastewater disposal or repeated laundering. The useful distinction for readers is between fungal pigment discovery, controlled textile testing and a validated consumer process; only the first two were studied here.