It is a form of blue-dyeing or blueprinting, where a dye-resistant paste is printed onto a cloth before it is dyed with indigo dye.
In the 18th century, blueprinting was also called porcelain printing because of the blue and white decor. It is a dyeing process for linen or cotton fabrics. It consists of a pattern of white on a blue background. These are reserve prints with so-called models, which have a protective compound printed on them, and dyed with indigo. As a result, the applied design remains white after dyeing since the resist paste prevents the dye from penetrating. Handcrafted blocks up to 300 years old are used by practitioners to apply designs to cloth, including regional patterns as well as generic designs and Christian themes.
It is important to understand that traditional indigo blue dyeing is closely related to the local culture of the region. The textile process involves preparing the raw materials, spinning them, weaving them, finishing them, printing them, and dyeing them. A large amount of traditional knowledge is derived from (usually family-owned) journals dating back to the nineteenth century and is passed on through observation and hands-on experience. Stakeholders feel a strong bond with the products they make, and the element embodies pride in a long-lasting family tradition.
Manufacturing and mechanical roller printing meant that blueprints are no longer produced in workshops. Only a few small handicraft businesses in Europe produce models and use the old printing techniques. Industrialization and mechanical roller printing is the end for most blueprints. Currently, mostly small and family-owned, run by the second to the seventh generation of printers. Each family studio requires cooperation from all family members, regardless of gender. Each member of the family takes part in every step of the production.
In Germany, there are twelve blueprinting workshops. The oldest still operating blueprint shop in Europe is located in Einbeck in Lower Saxony. There are also blueprinting workshops in Scheeßel and Jever in Lower Saxony. Among Bavarian master craftsmen are the hand print and dyeing Fromholzer in Ruhmannsfelden, which was founded in 1640, as well as the blueprinting business Henkenjohann & Sander in Bad Aibling. The Czech Republic and Slovakia each have three family-owned blueprinting firms, and Hungary has six. There are two traditional Austrian companies that produce blueprints - the Gutau Dyer Museum in Bad Leonfelden (also in the Mühlviertel region of Upper Austria) and the Blaudruck Wagner in Bad Leonfelden (also in the Mühlviertel region).
References
(https://ich.unesco.org/en/RL/blaudruck-modrotisk-kkfests-modrotla-resist-block-printing-and-indigo-dyeing-in-europe-01365) (https://de.wikipedia.org/wiki/Blaudruck#Heutige_Verbreitung)