Cologne brown – from van Dyck to modern times
Painting with humic substances?
If you frown now, you don't know Anthonis van Dyck. The Dutch painter is considered a genius of dark portraits and a pioneer in the material use of lignite and the containing humic substances, but let's start at the very beginning:
Van Dyck and Cologne brown
Sir Anthonis van Dyck was born in Antwerp in 1599 and learned painting from the age of ten. At the age of 16 he already owned a studio and quickly made his mark as a master. His especially dark, rich portraits let him travel far and get to know the upper echelon of Europe. For his coffee-brown color compositions he used a colorant that had already been used by lesser known painters before him, but only became famous through him: Van Dyke Brown, formerly also known as Cologne Brown or Kassler Brown, presumably after its discovery in North Rhine-Westphalia and Northern Hesse.
What is Cologne brown?
Van Dyke brown or Cologne brown is an organic pigment made of weathered, humic acid rich brown coal (Leonardite). At van Dyck’s time lignite was not a typical fossil fuel: since it is only very moderately suitable for this purpose, the first lignite briquettes (Klueten) were also called stink coal. Before Leonardite was used as an energy source, it was probably used as a colorant. In our time, it is rarely used as a dye – a prominent representative is the painter Bob Ross, world-famous for his TV series "The Joy of Painting". Instead, the material uses of Leonardite and the humic substances it contains are increasingly coming to the forefront.
Humic acids: a long tradition of useful applications
As early as 1840, German chemist Friedrich Ferdinand Fischer described the extraction of humic acids with potassium carbonate and their use as growth stimulators for plants. Building on this, more and more material applications of Leonardite and the humic substances it contains were discovered over time. Also in the paper and dye industry – closing the circle to van Dyck and his Cologne Brown after almost 500 years:
Humic substances in the modern paper industry
Humic acids not only saves time in paper dyeing, especially with dark colors - they also prevent toxic substances from entering the water during the manufacturing process. They are a valuable aid in paper processing with oils, waxes and resins and are of great value wherever non-aqueous liquids must be prevented from penetrating during certain steps in the paper production process. If van Dyck could experience this - he would probably have been pleased.