History of dyeing
Tapestry weaving is one of the oldest crafts, which became widespread in Western Europe in the early Middle Ages. Its origins go back to wool weaving - one of the most advanced forms of handicraft production, which separated from agriculture in the economically developed areas of Western Europe in the middle of the 11th century. Thanks to the knowledge of old Halo-Roman techniques and the proximity to the busy ports of Hansa, professional handicraft wool weaving started to take on an industrial scale. The techniques used in the production of wool fabrics were similar to the techniques of tapestry weaving, which has a long history.
In the medieval Netherlands fabric and tapestry production was one of the main industries, so there were numerous and well-organised dyers' associations in the largest textile towns. According to the shop statutes (ordonnance), approved by the city authorities and stipulating a clear division of labour, dyers had a monopoly on dyeing fabrics and threads. According to the approved rules, silk and woolen threads used in the manufacture of tapestries were dyed in leas. The art of wool dyeing began to develop in the south of Flanders. In the course of the historical development of cloth production, which also included dyeing, it began to move north, and by the fourteenth century it had spread to the cities of Brabant: Brussels, Bruges, Ghent, Louvain and Mechelen (Malines).
According to the ducal charter of 1306, the dyeing workshops in Brussels belonged to two different guilds: the masters of 'dyeing' (meestre van de ververen) and the masters of 'hot dyeing' (ketelknapen). As with all city guilds, the owners of dye shops were subordinated to the guild elders, the duaiens, who were elected each year from among the masters themselves and who represented their interests before the college of eschevens, the city representatives.
The ducal charter defined the groups of dyes that were to be used in the dye houses of the town. Each colour was to be produced using reworked dyes. Thus, for dyeing blue they used Isatis tinctoria L.; for red - Rubia tinctorum, Kermes(© Spodek M, Ben-Dov Y (2012)) (Kermesidae L.), which was imported from Eastern Europe and the Middle East and cost exorbitant money; for yellow - Reseda (Reseda luteola). From the middle of the 16th century, dyers in Europe began to use red dyes imported from overseas colonies in America: cochineal(Dactylopius coccus Costa L.) and Brazilian wood (Haematoxylum brasiletto L.). To obtain certain shades, mordants were used: tartar, alum, iron-tin and copper salts. From the beginning of the 16th century, vaida was gradually replaced by another indigofera (Indigofera tinctoria L.) as its colouring properties were much more effective.
By 1370 the differences in the ranks of the dye masters had gradually been replaced by differences in the dyeing technology and the dyeing raw materials used. These changes in the structure of the so-called 'junior' workshops (dyers) were reflected in the registry of the Guild of Clothmakers of Brussels in 1416-1417, which specified that dyeing masters constituted two different guilds. Since the late Middle Ages, blue dyers, who dyed cloth and thread in a cold solution, came to be called 'blauwevaerwers' or 'vat dyers' . Dyers specialising in blue used large wooden or stone vats in which the complex process of fermentation - the preparation of a dye bath - took place. The process of dyeing cloth and threads took quite a long time and was done in a cold solution. In Flanders the emblem of the blue dyers' guilds was a double-headed blue eagle on a silver background
Masters of dyeing in red ('rootvaerwers' -'roodververs'), were called 'hot' ('sieders' - 'zieders'), because when fabric and thread were first dipped into the dyeing vat, they were boiled together with the mordant salts. According to the established rules, a master was not allowed to work with fabrics or dyes for which he did not have permission. For example, a dyer who had permission to dye wool red and yellow could not dye it blue, and vice versa. The emblem of the master dyers was a golden eagle on a red background 
The dyeing workshops were usually situated on riverbanks, due to the need for a sufficient amount of clean water. The dye mixtures were heated in stone ovens, often in stone vats placed on top of the oven. Rolls of yarn were dipped into the dye and stirred with a wooden stick. At the end of the dyeing process, the yarns were rinsed in running water and pressed in wicker baskets. The rolls of yarn were then hung on sticks for drying.
In the sixteenth century, the Brussels dye shops, and especially the blue dyers, suffered from rivalry with other cities. The flourishing of Antwerp, as a trading centre for raw materials and textiles, in the last quarter of the 15th century was directly linked to the development of dye-making. Since Antwerp's workshops were not traditionally restricted by the strict regulations of the guild charter, many foreign dye masters moved to the European commercial capital. Here they could use colonial dyes and produce at lower prices than Brussels artisans.
Because the municipality of Brussels was keen to support local craft industries, it mandated that all fabric and tapestry manufacturers use yarn dyed only in the workshops of the Brussels blue dyers. In addition to protectionist measures, the city's administration welcomed foreign talent and technology into the city's dyeing industry.
Nonetheless, in 1582, an edict was passed that required foreign craftsmen to register with the city's guild, indicating a special policy towards foreign technology, as registration required the use of traditional dyeing production processes. Obtaining permission to use new dyes or technologies required special permission from the city authorities and the guild.
P.S. For the dye plants mentioned in this article, see the next section.