Traditional Fish Leather Dyeing Methods with Indigenous Arctic Plants

Abstract

Along the Arctic and sub-Arctic coasts of Alaska, Siberia, north-eastern China, Hokkaido, Scandinavia and Iceland, people have dressed in clothes or worn shoes made of fish skin for millennia. (Within this article, the terms fish skin and fish leather are used to indicate different processes of the same material. Fish skin: Skin indicates the superficial dermis of an animal. Fish skin is referred to as the historical raw material that is tanned following traditional methods such as mechanical, oiling and smoking tanning, using materials such as bark, brain, urine, fish eggs and corn flour. Fish leather is used to refer that the fish skin has passed one or more stages of industrial vegetable or chrome tanning production and is ready to be used to produce leather goods). These items are often decorated with a rich colour palette of natural dyes provided by nature. In this study, minerals and raw materials of plant origin were collected from riverbanks and processed by Arctic seamstresses who operated as designers, biochemists, zoologists, and climatologists simultaneously. During our research, an international team of fashion, tanning and education specialists used local Arctic and sub-Arctic flora from Sweden, Iceland, and Japan to dye fish leather. Several plants were gathered and sampled on a small scale to test the process and determine the colours they generated based on the historical literature and verbal advice from local experts. This paper describes the process and illustrates the historical use of natural dyes by the Arctic groups originally involved in this craft, building on the traditional cultural heritage that has enabled us to develop sustainable dyeing processes. The results are promising and confirm the applicability of these local plants for dyeing fish skins, providing a basis for a range of natural dye colours from local Arctic flora. The aim is to develop a moderate-sized industrial production of fish leather in this colour palette to replace current unsustainable chemical dyeing processes. This project represents an innovation in material design driven by traditional technologies, addressing changes in interactions between humans and with our environment. The results indicate that new materials, processes, and techniques are often the fruitful marriage of fashion and historical research of traditional methods, helping the industry move towards a more sustainable future.

1. Introduction

The historical significance of fish skin has often been overlooked within material culture studies, with archaeologists typically emphasizing their role as a food source rather than as a raw material [1]. The scarcity of surviving material culture from both plant and animal sources, creates gaps in the archaeological record [2]. However, traditional Indigenous practices reveal the versatility of fish skins, particularly salmon skin, which has been used widely for both sustenance and clothing [3].

The Indigenous Inuit, Yup’ik, Alutiiq, and Athabascan of Alaska; Siberian Peoples like the Ulchi, Nivkh, and Nanai; the Ainu from Hokkaido Island in Japan and Sakhalin Island in Russia; the Hezhe from northeast China; the Saami of northern Scandinavia, and Native Icelanders all have historical evidence of fish skin production.

These Peoples developed specialised techniques for harvesting and processing fish skin to craft suitable clothing, essential for survival in one of the harshest climates in the world. Fish skins were used for wind protection and insulation. Distinct costumes with stylistic variations in design, decoration and dyeing techniques throughout the Circumpolar North reflect resilience, cultural diversity, and the work of highly skilled individuals [4]. Arctic societies have constantly adapted to environmental change through material innovation and technological advances, often facilitated by interactions with both nearby and distant communities [5].

Historically, the natural hues of animal skins provided humans with their earliest access to colour, inspiring artists to create lavish artwork by blending the earth-toned colours found in different fish species. The Ainu People, for example, skilfully manipulated the subtle shades of fish skins to create intricate patterns on their garments (Figure 1A) [3]. Accounts of travels around Iceland in the mid-to-late 18th century describe Icelanders wearing traditional shoes made from the skin of the spotted wolfish (Anarhichas minor) [6]. The beautiful natural pattern of the skin, resembling that of a leopard, made dyeing unnecessary (Figure 1B).

Plant-based dyestuffs have long been used for leather dyeing, with tannins extracted from bark serving as one of the earliest known technologies [2,7]. Natural dyes extracted from flowers, fruits, wood, and bark [8], often supplemented with wood ash and metallic salts, have been used to achieve a range of muted hues [9]. These ancient dyeing techniques have contributed to the development of diverse artistic craftsmanship [10].

In Arctic societies, access to natural raw materials limited colour options to the subtle beauty of earth shades and tonal contrasts [2]. Traditional sources of natural dyes vary depending on climate and geography [11]. These dyestuffs, derived from plants and insects, can be categorised into direct dyes, insoluble vat dyes, and mordant dyes, each offering unique properties for colouring [12].

Yellow dyes, for instance, can be derived from a range of sources, including weld and dyer’s greenweed, while browns, greys, and blacks are achieved using tannin-bearing substances such as tree barks, nuts, and galls [12].

Indigo, sourced from various plants, introduced a deep blue hue to societies, diverging from the earth tones prevalent in traditional palettes [2] and has been widely used to dye panels decorating Nivkh and Nanai fish skin coats and boots (Figure 1C).

The use of natural dyestuffs from plant sources, often termed “green dyeing,” offers biodegradable and environmentally friendly alternatives to contemporary synthetic dyes [13,14].

Despite the rich history of fish skin use, studies on fish skin dyes remain limited, with conservators often focusing more on preservation techniques rather than the pigments or tannins used to produce the artefacts [2]. This paper aims to address this gap by assessing different fish skin dyeing processes using Indigenous Arctic and sub-Arctic plants, thereby contributing to a deeper understanding of traditional dyeing techniques and their cultural significance.

2. The Project

The FishSkin project, funded by the EU under H2020-MSCA-RISE-2018, brings together experts to explore the potential of fish skin as a sustainable raw material. Through practice-based research and interdisciplinary collaboration, fostering international partnerships we aim to develop natural dyeing techniques for fish leather while supporting local dyestuffs and traditional processes. Drawing on our experiences as tanners, dyers, designers, and educators, we aim to address sustainability challenges in the fashion industry by integrating design practices with environmental and social considerations. Four case studies conducted in locations such as Sigtuna in Sweden, Kyoto and Fujino in Japan, and Reykjavik in Iceland provide valuable insights into natural dyeing techniques for fish leather, laying the groundwork for future research and development efforts.

This project was supported by the Nordic Fish Leather tannery in Iceland which supplied the industrially tanned fish leather used in some of the samples. Empirical tests were carried out at Ars Tinctoria laboratory. In collaboration with Nordic Fish Leather and Ars Tinctoria laboratory we plan to experiment further to replace modern chrome-tanned fish leather with vegetable tanning methods, taking advantage of their very low environmental impact. Both institutions are partners of the EU-funded FishSkin project https://www.fishskinhorizon.org/ (accessed on 11 January 2024).

2.1. Project Aims

This paper aims to uncover the historical use of Indigenous Arctic plants for fish skin dyeing, gathering and recording geographical and historical information about them to identify various specimens and documenting their qualities within natural dyeing history. By consulting literary sources, as well as local experts, we aimed to explore the potential of these natural dyes. The focus was on reviving old traditions and local cultural heritage to discover sustainable processes for the future, contributing to collective knowledge [15]. Natural dyeing, using raw plant materials, offers an ideal approach to colouring while connecting products to specific places, people, and experiences. By adopting a restorative method of making, we aim to shift the focus from scarcity and extraction to abundance and regeneration [10].

2.2. Materials and Methods

2.2.1. Fish Leather a Food Waste by-Product

Fish leather is a by-product of the waste stream of the seafood industry [16] where fish are not killed solely for their skin, which represents only a minor part of the value of the animal. Using fish skin for leather production prevents the waste of this renewable resource. Industrially produced fish leather is exclusively sourced as a by-product of the fish farming industry.

When using fish skin from fish farms, it should be noted that some practices are highly controversial and that, in order to ensure quality, sustainability, and animal welfare, land-based fish farms are the best option. Moreover, the fish leather market risks increasing fishing pressure on certain species, and must rely on waste skins from active fisheries.

Fish leather is known for its high tensile, tear, and stitch strength due to its intersecting fibre pattern, making it durable over time. Despite its high performance and lower price compared to exotic skins, fish leather remains a niche product, unlikely to penetrate the mass market due to capacity constraints and its manual production process.

Nordic Fish Leather, the largest fish leather tannery globally, has been processing this material since 1994, drawing on Iceland’s ancient tradition of making wolfish skin shoes (Figure 1B) [17]. NFL tannery, using only Icelandic renewable energy, must ensure eco-friendly tanning processes despite being less polluting than other leathers production processes. They supply fish leather to fashion brands like Nike, Jimmy Choo, John Galliano, Christian Dior, Prada, and Salvatore Ferragamo. The tannery has revitalised this historic eco-luxury material, reviving ancestral tanning techniques and providing employment for the local coastal community [4].

The fish leather samples used for this project were a by-product of the seafood industry. Lotta Rahme’s tests were performed with farmed salmon from Norway and salmon skins were traditionally tanned by herself. The rest of the tests were executed with Icelandic-farmed salmon industrially tanned by Nordic Fish Leather.

2.2.2. Traditional Tanning Methods

Indigenous Arctic Peoples developed traditional tanning methods with considerable local differences. They could opt to soften the skins without any tanning solution, or they could alternatively choose to use three groups of tanning materials: fats, vegetable and mineral. To prepare the tanning bath, the early tanners used materials of animal origin such as urine, brains, liver, kidneys, bone marrow, fish oil, fish roe, butter, eggs, or materials of vegetable origin such as cornmeal, tree bark, leaves, gallnuts or a combination of the above [18]. Alum tanning, or “tawing”, a process that emerged from accidental immersion in alum-bearing waters, was also used in this project [19].

Lotta Rahme’s samples were fully tanned by herself from scratch using some of the traditional tanning methods mentioned using materials such as gallnut or sallow bark.

Samples dyed with Icelandic and Japanese natural dyes used chrome-tanned fish leather from the Icelandic tannery Nordic Fish Leather. Chrome tanning, now the most widely used method globally, involves immersing fish skins in a solution containing chromium sulphate [20]. This method, which takes just one day, produces thinner and softer leather compared to traditional techniques. The main advantages of mineral tanning over traditional tanning are convenience and cost-effectiveness. Commercially, chrome-tanned leather is more affordable than vegetable-tanned leather. However, due to its chemical-intensive nature, chrome tanning is less environmentally friendly and has potential environmental impacts.

2.2.3. Traditional Dyeing Methods

We used natural materials such as bark, pinecones, roots, flowers, leaves, galls, mushrooms, lichens, and seaweed to achieve our desired colours. All dye materials were prepared by hand, involving chopping, drying, and grinding to extract the pigment fully. Every mordant and modifier used was environmentally safe when diluted and released into soil. In our dyeing process, we employed a range of natural resources, resulting in various chemical and physical transformations. Using principles of bush chemistry [2], we integrated plant and animal materials, such as wood ash, urine, and tree bark, to produce acidic and alkaline solutions and mordants like alum or iron. Tannins were also used in colour fixation.

Dyestuffs were locally sourced to avoid harming endangered species or insect biodiversity. By favouring natural materials, we ensured that fish leather could eventually biodegrade and enrich the soil contributing positively to the ecosystem. We advocate for a shift away from fossil-fuel derived manufacturing processes and non-compostable materials in textile systems, employing low-impact, energy-efficient methods to minimise environmental footprint.

2.3. Collection and Processing of Plant Material: Extraction of Tannins and Dyes

Materials were chosen based on criteria such as abundance and availability. The bark of trees was collected for tannin extraction, dried under shade, and oven-dried for two days before being ground into a coarse powder using a mill [21]. The extraction of tannins from plant parts typically involves using water as a solvent, but the method can vary depending on whether solid/powder or liquid tannins are desired.

Plant collection and dyeing are best performed earlier in the growing season to obtain better colouring from younger plants and a more diverse colour palette [22]. The resulting colour depends not only on the plant selected but also on factors like location, weather conditions (dry or wet), and time of year.

2.4. Dyeing Process

For dyeing fibres, washing the material beforehand is usually recommended, but since fish leather comes ready for dyeing from tanning, this step was skipped. The prepared skin was treated with alum and soaked in cold water for over an hour. It was important to adjust the alum amount carefully, as fish skins are sensitive to pH levels. Using a deep stainless-steel pot is preferable to avoid affecting the dyeing process with other metals.

The soaked fish leather is heated in the pot, maintaining the water temperature, according to the tanning method used, from 25 °C to just below 70 °C. After cooling overnight, the leather is rinsed and ready for dyeing. Preparing the dye vat involves filling a large stainless-steel pot three-quarters full of water and adding the prepared plant material. The plants were typically cut into smaller pieces and crushed before being placed in the pot. After heating with the lid on for 20 min, the water began boiling, and then the heat was reduced to simmer for an hour. The resulting dye water is sieved, and the dyeing process was begun by immersing the material to be dyed in the vat, simmering for over an hour at a temperature adapted to the tanning method. After cooling, the skins were left to stand for one to two days, until the colour became stronger.

Fish skins are more delicate than other materials and cannot withstand high temperatures, which can result in less intense colours. Additionally, fish skins are sensitive to significant changes in acidity, or pH levels. It is crucial not to leave fish skins in baths with iron for extended periods, as this can make the skins more brittle. For the brightest and longest-lasting colours, tanning fish skins with gallnuts before dyeing is recommended.

3. Traditional Swedish Natural Dyes by Lotta Rahme

The roots of dyed textiles in Sweden trace back to archaeological findings in Birka (800 BC), revealing fragments of dyed fabric. Wild plants, including roots, berries, bark, leaves, lichen, and later fungi, served as the primary sources of dye fibre. These plants were typically gathered in late spring and summer, with some peasants selling dye plants to local dyers. Written evidence of plant dyeing can be found in Olaus Magnus’s “A Description of the Northern Peoples” [23]. Carl Linnaeus played a significant role in documenting locally used dye plants during his travels across Sweden. Numerous dye formula books from the 18th century, based on Linnaeus’s observations and other contemporary studies, have been preserved to this day. Brown dye, for instance, was commonly derived from bark, according to Linnaeus’s findings [24].

With 40 years of experience as a traditional tanner, Lotta Rahme (Figure 2) has learned techniques from women of various cultures who still uphold ancestral knowledge. Recognising the urgency in safeguarding and passing on these vanishing traditional skills, she has devoted herself to their conservation and transmission. Through teaching courses, authoring books, and producing films, Lotta has played a crucial role in regaining the title of Master Tanner and elevating traditional tanning to the status of Intangible Cultural Heritage in Sweden.

In the summer of 2021, Lotta Rahme spent time in Dalarna, west of Mora, choosing to use locally available plants for dyeing. Lotta adapted wool dyeing recipes for use with fish skins (Figure 3). Typically, wool yarn is pre-treated with a mordant such as alum and cream of tartar to ensure durable and long-lasting colours. Lotta opted to tan her skins with gallnuts or sallow bark. Additionally, she sometimes added alum, salt, or cream of tartar directly to the dye bath as needed.

3.1. Gallnut Tanning

Gallnuts are pathological excrescences formed on oak leaves in response to certain insect bites, creating a protective tissue around the eggs [21]. These galls contain a high concentration of tannins, making them valuable for tanning purposes. Oak and sumac gallnuts (Rhus) are particularly prized for their 40% to 70% gall tannin content [25]. This traditional tanning method has ancient roots, with practices dating back to Mesopotamia [26], where gallnuts were ground and boiled to produce colours ranging from dirty yellow to brown. To achieve black dye, the fibre is often mordanted with ferric alum or iron mud [27]. The Greek philosopher Theophrastos of Eresos also documented the use of gallnuts for tanning and dyeing materials [28,29].

Lotta Rahme finds that skins tanned with gallnuts yield the brightest and longest lasting colours. For this project Lotta tanned eleven salmon skins with gallnuts, a vegetable tanning method that produces white leather (Figure 4).

3.2. Sallow Bark Tanning

Tan, primarily found in tree bark, varies in quantity depending on the season, age, and size of the trees. The inner bark contains the highest proportion of tan, while the epidermis usually contains none [21]. Vegetable tanning was discovered when hides and skins thrown into pools of rainwater or bog water absorbed the tannin from tree bark [19].

Alder (Alnus) bark is widely used by Arctic Peoples for skin colouring, particularly among the Saami. The bark is boiled in water or chewed, spit on the skin, or rubbed in to produce a red-brown colour. Sometimes ash is used in the alder bark extract to enhance the colour [30]. In northern Europe, local tree barks like birch (Betula), willow (Salix), larch (Larix), and spruce (Picea) are the main vegetable tanning materials [25].

Salmon skins can be tanned with sallow bark (Salix caprea) (Figure 5), which produces soft, smooth, light brown leather. The bark is best peeled from branches in spring when it contains the most tannin. After boiling the bark in water for an hour, the skins are placed in the solution once it cools to 20 degrees Celsius. The bark bath is stirred and strengthened over a period of up to 10 days. To obtain a black skin, the skins are soaked for 2 h in a solution containing sallow bark and iron.

3.3. Dyeing with Lichen

Lichens have long been used as dye plants in Nordic countries, producing a hue known as “moss brown.” Linnaeus documented their use as early as 1732, particularly noting their collection after rain when they are easier to scrape off stones [24]. In Sweden, the collection of lichens was once an important source of income, with Umbilicaria pustulata and Parmelia saxatilis being commonly collected species [31]. Byttelet, a red dye made from crabseye lichen (Ochrolechia tartarea), was also widely used, with significant quantities being exported from western and southern Sweden in the late 18th and early 19th centuries [32].

Lotta Rahme discovered dyeing recipes with lichen in J.P. Westrings’ book ‘Svenska Lafvarnas Färghistoria’ [33] (Figure 6). Given the endangered status of the tiny beard lichen Usnea glabrata in Sweden, she opted to use herringbone beard lichen (Usnea dasopoga) instead.

For the herringbone beard lichen (Figure 7), 50 g of the beard lichen was boiled in 3.5 litres of water for 3 h, resulting in a 1-litre solution to which 30 g of alum was added. The skins were soaked in a bath for 24 h.

Similarly, 54 g of horsehair lichen (Figure 8) (Bryoria capillaris), was boiled for 4 h in 3.5 litres of water to give a 1-litre solution, to which 30 g of alum was added. The tanning baths were allowed to cool to 25 °C before the skins were placed in them. The skins were left to soak for 24 h in the bath.

3.4. Dyeing with Roots

Roots have historically been important in traditional dyeing practices, with various cultures sourcing them to achieve desired colours. The technique of tanning the skin with tormentil rhizomes dates to the late sixteenth century and is a known practice among the Saami and settlers in northern Scandinavia and along the Baltic coast [24]. Tormentil, renowned for its medicinal properties, has been used as a dye plant due to its availability when other tanning plants were limited. The Saami in northern Sweden combined the rhizomes of tormentil (Potentilla erecta) with grey elder bark to produce a red dye substance [24].

Lotta Rahme used roots from tormentil (Figure 9) (Potentilla erecta), totalling 157grams, which were collected in July and dried. These roots were simmered in 2 litres of water for 1 h, resulting in 7 decilitres of solution. The skins were then soaked in the bath for 36 h.

3.5. Dyeing with Mushrooms

Sweden’s diverse flora and climatic conditions have endowed it with a rich variety of mushrooms, which have been used in various applications. Mushrooms contain essential minerals such as calcium, iron, phosphorus, potassium, and copper, which play a crucial role in natural dyeing by acting as fixatives that help the dye adhere to fibres, particularly iron and copper [27]. While the use of mushrooms for dyeing is a relatively recent practice in Sweden compared to the historical use of lichens in the eighteenth and nineteenth centuries, recently there has been a resurgence of interest in using mushrooms for dyeing wool and other natural fibres, owing to the relatively straightforward dyeing process [24].

Lotta Rahme used surprise webcap mushrooms (Figure 10) (Cortinarius semisanguineus), totalling 40 g, which were dried. These mushrooms were boiled for 40 min in 2.5 litres of water, resulting in 1.2 litres of solution. Additionally, 25 g of alum and 12 g of tartaric acid were added to the solution. The skins were immersed in a bath for 22 h.

4. Icelandic Natural Dyes by Katrín María Káradóttir and Sigmundur Páll Freysteinsson

Natural dyeing is a longstanding tradition in Iceland dating back to the settlement period, with wool, cotton, and linen being the primary materials dyed. Due to its sub-Arctic climate, Iceland has a relatively limited plant diversity compared to other regions. While Iceland boasts approximately 500 vascular plant species, Norway has around 1,300, and the UK has between 4,000 and 6,000. This reduced plant diversity in Iceland results in fewer options available for natural dyes compared to more biodiverse regions [34].

The decrease in plant diversity and the rise of invasive plant species could also affect the availability of natural dye sources [22]. While Icelandic plants have historically been used for dyeing, challenges exist in obtaining certain colours, such as red/pink, leading to the importation of materials like Rubia tinctorum for specific shades.

Traditional Icelandic plant dyeing has been developed by Katrín María Káradóttir (Figure 11A), a professor in fashion design and the principal investigator of the Horizon 2020 FishSkin project at the Icelandic University of the Arts, along with Sigmundur Páll Freysteinsson, a fashion designer who specialises in traditional natural dyeing techniques (Figure 11B). This project involved gathering a variety of plant specimens and conducting dyeing tests at the textile workshop of the Iceland University of the Arts in Reykjavík. The skins to be dyed were tanned at the Icelandic tannery Nordic Fish Leather in Sauðárkrókur, with an absolute minimum of chromium; therefore, the skins could tolerate much higher temperatures than the skins tanned only with vegetable tannins. The plants tested included flowers and leaves of lupine (Lupinus), wood cranesbill (Geranium sylvaticum), tansy (Tanacetum vulgare), bark of birch (Betula), dye lichens, northern dock (Rumex longifolius), heather (Calluna vulgaris), bearberry (Arctostaphylus) and cones of spruce (Picea). Additionally, experiments with alternative materials like the dulse (Palmaria palmata, red algae) and toothed wrack (Fucus serratus, brown algae), both seaweeds (algae) from the ocean were explored to enhance the variety of the dyed skins.

4.1. Icelandic lichens

In Iceland, various species of lichen, including salted shield lichen (Parmelia saxatilis), dye lichens, and rock lichens, have been historically used for dyeing purposes. These lichens contain acids that make them suitable for dyeing, and they can produce brownish colours ranging from dark to light tones, as well as red-brown hues. However, due to their rarity and slow growth, they are not suitable for large-scale industrial dyeing but can be used for limited-edition projects. The over-picking of lichens has led to their classification as an endangered species requiring protection.

For this project, 300grams of a dye lichen was collected from Langanes, with the permission of the landowner (Figure 12A). The lichens were dried before being transported back to Reykjavík. In the dyeing process, the lichens were placed in a deep dye pot overnight and then alum-mordanted fish leather was added to the pot. The mixture was heated to just below 70 °C for over an hour and the fish skin was left in the dye bath for two days before being removed, rinsed, and stretched to dry. The resulting fish skin exhibited a brown colour with a soft texture and minimal clumping of the roe (Figure 12B).

4.2. Icelandic Seaweed

Seaweed, marine algae, encompasses a rich diversity, with over 1500 green species, 200 brown species, and more than 7000 red species. They offer a wide range of properties, making them versatile resources that can be used in numerous ways. Foraging for seaweed remains a fundamental practice, akin to traditional land-based farming. In Iceland, a country surrounded by lush coastal areas, seaweed is abundant.

For Katrín María Káradóttir, the process of exploring seaweed for natural dyeing began with foraging on the coast near her home where she collected various types of algae, including dulse (Palmaria palmata) and toothed wrack (Fucus serratus) (Figure 13A).

These species provide a subtle palette of colours (Figure 13B), ranging from browns and greens to golds and subtle purples. Red/pink has been very difficult to obtain from Icelandic plants, but the roots of both yellow bedstraw (Galium verum) and northern bedstraw (Galium borale) have been successfully used. However, the roots of these plants are very small, and the process is so time-consuming that it is believed that these plants have only been used to dye embroidery thread in small quantities [34]. Therefore, Icelanders have for centuries imported a relative, Rubia tinctorum, to easily obtain pink shades, even though it is possible to obtain it from Icelandic nature.

4.3. Lupine Flowers

Lupine (Lupinus), although not originally native to Iceland, has thrived since its introduction, with records dating back to 1885. It has spread across the country and is commonly used for large-scale land reclamation efforts. Due to its abundance, lupine is well-suited for industrial dyeing purposes.

Both the flowers and leaves of lupine offer potential for dyeing. When using lupine flowers (Figure 14A,B), which yield a green hue, a test was conducted by boiling 180 g of flowers to create a dyeing solution. Adding fish leather treated with alum to this solution resulted in a beautiful light green colour with darker shades interspersed.

Similarly, dyeing with lupine leaves (Figure 15A,B), involved dipping fish skin pre-treated with alum into a dye vat that had been created by boiling 136 g of lupine leaves. The result was a dark brown colour with subtle yellow undertones.

4.4. Wood Crane’s Bill

The wood cranesbill (Geranium sylvaticum) is a bushy herbaceous perennial plant that typically reaches heights of up to half a meter. This plant thrives in various habitats, including grove-like and moist heath forests, wet meadows, fens, and morasses across Iceland. The species name “Geranium sylvaticum,” meaning “of woodland,” reflects its natural habitat preference. In folklore, it is also known as “Odin’s Grace” as it was historically used to dye war cloaks blue-grey, believed to offer protection to soldiers in battle. Legend has it that carrying wood cranesbill brings prosperity and wealth [35].

The plant is known for producing black and grey colours when boiled with bog iron from marshes. For dyeing purposes, 600 g of wood cranesbill (Figure 16A,B) was boiled to create a dye solution, and fish skin pre-treated with alum was immersed in the solution to create a sample. The resulting colour was a grey-green hue.

5. Traditional Japanese Dyes: Matsuyama Issey and Mitsuhiro Kokita

Matsuyama Issey (Figure 17B) is a fifth-generation artisan specialising in the traditional Japanese dyeing of religious monk robes. Growing up watching his father and grandfather practice this ancient craft, Issey decided to continue his family’s tradition.

Mitsuhiro Kokita (Figure 17B), a fashion designer and associate professor, in the Fashion Department, Faculty of Popular Culture, Kyoto Seika University, and the Japanese principal investigator of the Horizon 2020 FishSkin initiative, sought collaboration with Matsuyama-san to develop a new palette of fish skin colours using traditional Japanese vegetable dyes.

Matsuyama Issey specialises in a traditional dyeing technique known as shinzen (dip-dyeing). He draws inspiration from historical records like the “Nuidono-tsukasa-shiki” and “Kusagusa-noyoudo,” which comprehensively detail various dyes and colouring techniques used during the mid-Heian period (10th century). These records mention dyeing materials such as sappanwood (Biancaea sappan), roots of gromwell (Lithospermum), safflower (Carthamus tinctorius), madder (Rubia argyi), and Gardenia, as well as mordants like Camellia ash, straw ash, wood ash, alum, and tessho (ferrous acetate), each contributing to a wealth of Japanese dyeing traditions [36].

For the traditional shinzen (dip-dyeing) process, skins were washed with water at a temperature of 40 °C for 5 min. Mordanting was performed at a water temperature of 40 °C for 40 min. Following this, they were washed in soapy water at a temperature of 50 °C for 10 min and then dried. The dyeing was performed at a water temperature of 40 °C for 50 min. After dyeing, the skins were washed in cold water, followed by hot water, and then washed once more in cold water before being left to dry. Rakkudai maintained a pH level of 4, sappanwood maintained a pH level of 6, and Scutellaria maintained a pH level of 6.

Skins were reoiled using a 6% fish oil-based medium, 2% phosphoric acid, and 1% emulsifier, maintaining a pH level of around 4 to 5. The wetting took 20 min and the reoiling process took 60 min. After reoiling, 0.5 g of formic acid was added three times at 15 min intervals. The pH after the reoiling process was around 3 to 4. The skins were softened in a drum with a drum temperature of 40 °C at 25.92 rpm with 4 golf balls for 180 min, maintaining a pH level of around 5. To improve colour fastness, different mediums were used: (1) five layers of spray, (2) one layer of Clear TS1125, (3) 0.5 layer of non-brushing thinner, and (4) two layers of lacquer thinner.

5.1. Koganebana/Scutellaria

The Baikal skullcap or Chinese skullcap (Scutellaria baicalensis) (Figure 18A), a perennial plant indigenous to the northern mountains of China, found its way to Japan during the Kyōhō era (1716–1736), when seeds were imported from Korea and cultivated in the botanical gardens of the shogunate. Initially grown for medicinal and aesthetic purposes in Japan, it later became valued as a natural dye. Scutellaria offers good lightfastness and can produce deep colours when used with alum or iron mordants. The main pigment composition found in the root of the large-flowered skullcap (Scutellaria baicalensis) is baicalin, offering not only vibrant hues employed for colouration in textiles but also the added benefit of its medicinal properties [37]. The resulting colour was a beautiful intense yellow (Figure 18B).

5.2. Rakkudai/Lac dye

Rakkudai (Figure 19A), commonly known as lac dye, is derived from the scale insect Kerria lacca, which is predominantly found in Southeast Asia. These insects are either collected from the wild or cultivated for their resin. When the female lac insects invade trees, they secrete a resin that forms a protective covering around them, which is harvested by breaking it off the branches. The dye is then extracted from the stick lac before it is used for dyeing cloth.

The history of lac dye in Japan dates to the Nara period (710-784), when it was introduced to the country. Over time, lac dye became widely used, particularly during the Edo period (1603-1867). It was commonly employed to dye cotton imported from China, used in Yuzen dyeing, and served as a pigment for painting. Aside from its role as a natural dye, lac has a longstanding history of medicinal use in Japan [38]. A beautiful, intense pink colour was obtained after the dyeing process (Figure 19B).

5.3. Suoh/Sappanwood

Sappanwood (Biancaea sappan) (Figure 20A), a small tree belonging to the legume family and native to India, thrives in tropical regions. Its use as a natural dye in Japan traces back to ancient times, with records of its importation during the Nara period (710-784). During the Heian period (794-1185), sappanwood was highly prized for its ability to produce exclusive shades of red and purple, primarily reserved for the emperor and court nobles. Commoners, on the other hand, predominantly used indigo and earthy browns for their dyeing needs [39].

In the dyeing process, finely chopped sappanwood chips are boiled in water with a small amount of rice vinegar to create a dye bath. The resulting liquid, once strained, is then used for dyeing. Depending on the mordant and dyeing method, sappanwood can produce various tones of pink, red and purple, offering a versatile palette [40]. The final colour obtained from this method was a light pink shade (Figure 20B).

6. Traditional indigo Dyeing: Takayuki Ishii, Elisa Palomino and Lotta Rahme

Historically, earth tones dominated traditional colour palettes until the widespread use of indigo, which introduced a deep blue hue to many societies [2]. Indigo, derived from various plants, has been known since ancient times, with evidence of its use dating back to ancient Egypt [41,42].

Dyer’s knotweed (Persicaria tinctoria, syn. Polygonum tinctorium) was introduced to Japan from China [43]. During the Edo period (1603–1868), Awa indigo dye appeared in markets across Japan, enriching the economy and culture. Artisans in Tokushima continue the legacy of Awa indigo today. “Sukumo” refers to the natural dye derived from the indigo plant, a member of the Polygonaceae (knotweed family), whose leaves are dried and fermented [44]. However, the success of Sukumo indigo dyeing is subject to land quality, environmental conditions, water purity, humidity levels, and temperature fluctuations. Thus, achieving consistent results requires continual experimentation.

Awa indigo dyeing has been preserved and passed down through generations by indigo masters. Lotta Rahme (Figure 21), and Elisa Palomino (Figure 22A), a research associate at the Smithsonian Arctic Studies Center and principal investigator of the Horizon 2020 FishSkin project at Central Saint Martins, University of the Arts, London, have teamed up with Takayuki Ishii (Figure 22A), a master indigo dyer working in the Fujino mountains in Japan, to create a new range of fish skin shades using traditional Japanese indigo.

It takes almost a year to produce Awa indigo. Takayuki cultivates his own, beginning with planting the seedlings in spring. In summer, the matured plants are harvested, and their leaves (Figure 22B) are carefully ground to a fine consistency before being thoroughly dried and stacked in his “Nedoko” or bed. Sukumo, the resulting mixture, holds the indigo colour pigments. However, these pigments are not water-soluble in their natural state and require a transformation. Initially, the indigo leaves are combined with alkaline substances like lime and wood ash lye in a container. This process converts the pigments (indigotin) into water-soluble yellowish green components (leuco-indigotin). The mixture is left to ferment for a week under meticulous temperature control, maintaining a pH level of 11.5. At Takayuki’s workshop, there are several vats that are nestled into the floor (Figure 22B), and thermally insulated, maintaining a stable temperature of around 20 °C, each is at varying stages of maturity, resulting in a range of colour strengths.

The process begins by immersing fish skins in the indigo vat for four minutes, followed by airing them for another four minutes. This allows the dye to penetrate and imbue the material with colour. As the fish skins are exposed to air, the water-soluble leuco-indigotin molecules react with oxygen, returning to their water-insoluble state, and the indigotin pigments, are now fixed to the fibres. After thorough washing in water, any excess or unfixed colour substances are rinsed away, revealing a vibrant indigo hue. The fish skins were dyed once, twice, and three times to achieve varying intensities of colour (Figure 23A,B).

Takayuki’s innovative approach to Sukumo production has been documented in his book “The Way of Indigo,” which outlines a method using a small quantity of leaves. This approach challenges traditional notions of Sukumo production, previously believed to require large quantities of dried leaves [45]. The decline in Sukumo artisans and the increase in demand have disrupted the balance between supply and demand, making Sukumo indigo dyeing less accessible. Takayuki’s Sukumo recipe, developed over ten years of research and collaboration, offers a solution to this challenge.

7. Light Fastness Tests

Colour fastness tests were performed at the Italian analytical laboratory Ars Tinctoria. Fastness properties were analysed following updated ISO standards. The key properties to be tested were resistance to direct sunlight, which is an important factor, and the intensity of natural light and UV content, which fades colours and intensifies the hue of natural dyes, thus altering the colour.

ISO 15701:2022 (IULTCS/IUF 442) Leather—Colour fastness to migration into poly-meric material [46]: For this test, migration was tested on standard PVC layers. This test helps to understand if there will be potential colour migration into plastic materials, and eventual stain of polymeric finishing applied, by contact with neighbouring materials. The results of this test on the indigo-dyed fish skins can be observed in Figure 24A (rate 5 / 5 for greyscale, where the value 5 represents the highest standard). Fish skins tanned with gallnut and dyed with either herringbone beard lichen (Usnea dasopoga), horsehair lichen (Bryoria capillaris) or roots of tormentil (Potentilla erecta) also scored 5 / 5 for greyscale. Fish skins dyed with rakkudai scored 5, those dyed with sapanwood scored 4/5, and those dyed with Scutellaria scored 4. Fish skins dyed with toothed wrack (Fucus serratus) scored 5. Such excellent results together allow for combining the dyed fish skin obtained with any other neighbouring material without the risk of colour transfer.

ISO 11641:2012 (IULTCS/IUF 426) Leather—Colour fastness to perspiration (on multifibre) [47]: This test was developed to understand eventual colour fading or migration into different textile fibres with artificial acidic perspiration. A compendium of different fibres, from acetate, cotton, nylon, polyester, acrylic and wool was used in this test. The results for the indigo-dyed fish skins in Figure 24B show a light stain on nylon (rated 4/5), while other types of fibres showed excellent performance (5). Fish skins tanned with gallnut and dyed with herringbone beard lichen (Usnea dasopoga) showed a light stain on nylon, cotton, acetate (rated 4/5), and wool (4). Those dyed with horsehair lichen (Bryoria capillaris) scored 5 for acetate, cotton, polyester, and acrylic; 3 for nylon and 2 for wool. Fish skins tanned with gallnut and dyed with roots from tormentil (Potentilla erecta) showed a stain on wool (3/4) polyester, acrylic (4) acetate, cotton, and nylon (4/5). Fish skin dyed with sappanwood scored a low value of 3 for nylon, 4 for acetate and 4/5 for cotton, polyester, acrylic, and wool. Fish skins dyed with Scutellaria show a light stain on nylon and wool (rated 4/5), while other types of fibres showed excellent performance (5). Fish skins dyed with rakkudai showed a light stain on all fibres 4/5. Fish skins dyed with toothed wrack (Fucus serratus) showed a light stain on acetate, cotton, and nylon (4), while they showed excellent performance for polyester, acrylic, and wool (5). Also, in this case staining was rated against greyscale where perfect values were represented by a rating of 5.

ISO 105-B02:2014 Textiles—Tests for colour fastness—Part B02: Colour fastness to artificial light: Xenon arc fading lamp test [48]: This test emulates the weathering of a colour sample by exposition to natural solar light. In this case, samples’ colour fading is rated against a blue scale on fabrics representing values 1 to 8, where 8 is the highest standard. The lightfastness obtained for the indigo-dyed fish skins (Figure 24C) was 2, which was a very weak result. Fish skins dyed with toothed wrack (Fucus serratus) scored 3. Fish skins dyed with rakkudai scored 3/4, those dyed with Scutellaria scored 3, and those dyed with sapanwood scored an even lower value (1). When using these dyes, it is recommended to avoid direct sunlight. However, fish skins tanned with gallnut and dyed with beard lichen (Usnea dasopoga) scored a remarkable 8 and those dyed with horsehair lichen (Bryoria capillaris.) scored 7. Fish skins tanned with gallnut and dyed with roots from tormentil (Potentilla erecta) scored 7.

The colour fastness tests showed sufficient light fastness, considering the fact that all samples tested were dyed with natural dyestuffs. The best results of the three different tests were from the fish skin samples tanned with gallnut and dyed with herringbone beard lichen (Usnea dasopoga), horsehair lichen (Bryoria capillaris), or with roots from tormentil (Potentilla erecta), on all portions of the sample tested for 24 h.

8. Conclusions

The dyeing techniques explored in this paper demonstrate the intricate relationship between geographical location, available natural resources, and local tradition and culture. Throughout history, the diverse arrays of colourants used serve as a testament to human ingenuity and creativity in discovering and refining dyestuffs from nature.

While synthetic dyes gained prominence in the mid-19th century, the resurgence of interest in natural dyes today aligns with the emerging sustainable movement. Natural dyeing not only offers beautiful colours but also promotes ecological consciousness by using renewable resources while supporting local livelihoods.

Fashion design, deeply intertwined with material culture, has the potential to foster deeper relational connections between people and their environment. By engaging with natural raw materials and dyes, fashion designers can create products that not only adorn the body but also contribute positively to ecosystem health.

However, challenges remain in integrating natural dyes into industrial production due to factors such as low yield and labour costs. Nonetheless, local small-scale initiatives are viable for meeting the current demand for natural dyes while providing economic opportunities for local communities.

Traditional tanning and dyeing techniques, offer environmentally friendly alternatives with unique properties. These techniques, although time-consuming and requiring specific skills, provide insights into sustainable material processing methods that can be adapted for modern use.

This research highlights the importance of understanding and preserving traditional practices and their biochemical logic to reconnect with our environment offering new perspectives on the interactions between people and nature.