Polish cochineal (Porphyrophora polonica), also known as Polish carmine scales, is a scale insect formerly used to produce a crimson dye of the same name, colloquially known as “Saint John’s blood”. The larvae of P. polonica are sessile parasites living on the roots of various herbs—especially those of the perennial knawel—growing on the sandy soils of Central Europe and other parts of Eurasia. Before the development of aniline, alizarin, and other synthetic dyes, the insect was of great economic importance, although its use was in decline after the introduction of Mexican cochineal to Europe in the 16th century.
Ancient Slavs developed a method of obtaining red dye from the larvae of the Polish cochineal. Despite the labor-intensive process of harvesting the cochineal and a relatively modest yield, the dye continued to be a highly sought-after commodity and a popular alternative to kermes throughout the Middle Ages until it was superseded by Mexican cochineal in the 16th century.
Perennial knawel, the chief host plant of the Polish cochineal
Similar to some other red dyes obtained from scale insects, the red coloring is derived from carminic acid with traces of kermesic acid. The Polish cochineal carminic acid content is approximately 0.6% of the insect’s dried body weight. The insects were harvested shortly before the female larvae reached maturity, i.e. in late June, usually around Saint John the Baptist’s day (June 24), hence the dye’s folk name, Saint John’s blood. The harvesting process involved uprooting the host plant and picking the female larvae, averaging approximately ten insects from each plant. In Poland, including present-day Ukraine, and elsewhere in Europe, plantations were operated in order to deal with the high toll on the host plants. The larvae were killed with boiling water or vinegar and dried in the sun or in an oven, ground, and dissolved in sourdough or in light rye beer called kvass in order to remove fat. The extract could then be used for dyeing silk, wool, cotton, or linen. The dyeing process requires roughly 3-4 oz of dye per pound (180-250 g per kilogram) of silk and one pound of dye to color almost 20 pounds (50 g per kilogram) of wool.
Polish military commander, Stefan Czarniecki (1599–1665), in a crimson costume typical of Polish magnates
Polish cochineal was widely traded in Europe during the Middle Ages and the Renaissance. In the 15th and 16th centuries, along with grain, timber, and salt, it was one of Poland’s chief exports, mainly to southern Germany and northern Italy as well as to France, England, the Ottoman Empire, and Armenia. In Poland, the cochineal trade was mostly monopolized by Jewish merchants, who bought the dye from peasants in Red Ruthenia and other regions of Poland and Lithuania. The merchants shipped the dye to major Polish cities such as Kraków, Gdańsk (Danzig), and Poznań. From there, the merchandise was exported to wholesalers in Breslau (Wrocław), Nuremberg, Frankfurt, Augsburg, Venice, and other destinations. The Polish cochineal trade was a lucrative business for the intermediaries; according to Marcin of Urzędów (1595), one pound of Polish cochineal cost between four and five Venetian pounds. In terms of quantities, the trade reached its peak in the 1530s. In 1534, 1963 stones (about 30 metric tons) of the dye were sold in Poznań alone.
The advent of cheaper Mexican cochineal led to an abrupt slump in the Polish cochineal trade, and the 1540s saw a steep decline in quantities of the red dye exported from Poland. In 1547, Polish cochineal disappeared from the Poznań customs registry; a Volhynian clerk noted in 1566 that the dye no longer paid in Gdańsk. Perennial knawel plantations were replaced with cereal fields or pastures for raising cattle. Polish cochineal, which until then was mostly an export product, continued to be used locally by the peasants who collected it; it was employed not only for dyeing fabric but also as a vodka colorant, an ingredient in folk medicine, or even for decorative coloring of horses’ tails.
With the partitions of Poland at the end of the 18th century, vast markets in Russia and Central Asia opened to Polish cochineal, which became an export product again—this time, to the East. In the 19th century, Bukhara, Uzbekistan, became the principal Polish cochineal trading center in Central Asia; from there the dye was shipped to Kashgar in Xinjiang, and Kabul and Herat in Afghanistan. It is possible that the Polish dye was used to manufacture some of the famous oriental rugs.