Woad and Blue Uniforms


Oxidizing the woad solution with an old mixer.

Today I harvested my woad and processed it to make a blue dye for dying my wool. It seemed late to harvest, but the woad was still lush and green so I decided to try it. I found a good site on the internet from a woman in the U.K. who makes and also sells the powdered dye. Aerating the solution causes the dye to oxidize. This causes the dye to form a precipitate which you can then separate from the liquid to make a powder. The powder allows for longer term storage. My dye is settling now.


French soldier. The steel helmet and “horizon blue” uniform indicate this is no earlier than 1915 as that is when the helmet was introduced. Before that, they just wore a brimmed cap.

As I was making the dye though, it got me wondering what dye they used for the “horizon blue” uniforms the French soldiers wore. It turns out that woad, used for dying wool in Europe for millennia, was finally usurped in the 1700s by indigo from India and other places in the far east. Indigo creates deeper and darker blues than woad. By the late 1800s synthetic dyes were becoming common. A synthetic indigo dye was launched in 1897 by a German scientist, Adolf von Baeyer. At the time, the production of natural indigo was around 19,000 tonnes, but by 1914, it was down to only 1000 tonnes having been replaced by synthetic indigo. Baeyer received the Nobel Prize in chemistry in 1905 for his work on chemical dyes.

So the “horizon blue” uniforms of the French soldiers would have been made from indigo-dyed wool, but it was undoubtedly the synthetic version.

The Chemists’ War

Fritz Haber, brilliant chemist with the dubious title of "the father of chemical warfare."

Fritz Haber, brilliant chemist with the dubious title of “the father of chemical warfare.”

While researching various chemistry inventions of World War I (often called the Chemist’s War), I came upon an interesting and important player in the War, that of the German chemist, Fritz Haber. Haber is often given the notorious title of ‘the father of chemical warfare’ because he developed chlorine gas and oversaw some of the initial German deployments of chlorine gas on the Western and Eastern Fronts. He was also involved in gas mask technology and the development of phosgene and mustard gasses which were even more insidious than chlorine. He is also known for the Haber-Bosch process which involves synthesizing ammonia from atmospheric nitrogen gas to make fertilizer and explosives.

After the war broke out in 1914, the British initiated a naval blockade of Germany which dramatically limited raw materials including fertilizer and food coming into the country. This deprivation of both the military and civilian population is often cited as one of the major reasons for the German surrender in 1918. It is estimated that at least half a million German civilians died directly as a result of the lack of food and nutrition, but many millions suffered. The industrialization of the Haber-Bosch process allowed Germany to create its own fertilizer rather than rely on foreign sources no longer available due to the blockade. Haber won the Nobel Prize in chemistry for this process in 1918. Because of this process, the population of the Earth has been able to increase dramatically in the twentieth century as at least one third of the current population relies on food grown with fertilizers created using the Haber-Bosch process.

Clara (Immerwahr) Haber, first woman Ph.D. in Germany.

Clara (Immerwahr) Haber, first woman Ph.D. in Germany.

While Haber, a brilliant chemist, strong German nationalist and militarist, is interesting and accomplished many things in the realm of science, I found his wife and fellow chemist, Clara Immerwahr, even more so. Clara was the first woman Ph.D. in Germany, also in chemistry, who worked on metal solubility. Like most men of the time period, Haber wanted her to be a stay home wife and manage the home and children, while she wanted to continue doing chemistry research. His had the stronger will, and she became increasingly frustrated and angry over the course of her marriage and not making full use of her abilities. She opposed her husband’s involvement in the war and his weapons research wanting him to use chemistry to help people rather than for killing.

In April, 1915, Haber supervised the deployment of chlorine against the French at Ypres, Belgium in which the French suffered over 6000 gas related casualties. On May 2, 1915, the day before Haber was scheduled to go to the Eastern Front for a similar deployment against the Russians, Clara and Fritz argued bitterly. The result was that Clara shot herself with Fritz’s service revolver in the garden. Their 13 year old son and only child, Hermann, found her, and she died moments later in his arms. Haber didn’t change his plans for the next day, but left his son and dead wife and went to oversee the gas attack on the Eastern Front.

The story of Fritz Haber, Clara Immerwahr, and their son Hermann (who committed suicide in 1946 apparently over the shame of his father’s involvement in chemical warfare) is a tragic story of love, hate, and chemistry; the ultimate chemists’ war.