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By Carina Magyar in Herbs —

II: Glasswort

The sad story of the king's chemist.

duodi, the 12th of Thermidor, Year CCXXXI.
Glasswort just hanging out. Photo via Wikimedia Commons.

Good morning. Today is duodi, the 12th of Thermidor, Year CCXXXI. We celebrate la salicorne, an herb from the swamps used to make glass and soap.

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Prior to glassmakers from Venice arriving in medieval England to share their techniques for making clear glass, this plant had no name in English, being just an unlovely clump of nobbled stems that grows in salt marshes and never flowers. The Venetians eagerly harvested the plant they recognized from their Mediterranean home and burned it, then mixed the ashes in water. Once any remaining dirt was filtered out of that water, the solution was left to evaporate, and what was left behind was about 75 percent potash and 25 percent sodium bicarbonate captured by the saltwater-loving plant, and produced much clearer glass than what was made from wood-burned potash. From then forward, it was known as the glass plant, or glasswort. In Spain, the same plant was processed the same way for use in soapmaking, which became known as barilla soap. 

Glass was still a luxury item in the 18th century. Glass itself was not rare, but money could buy the largest, strongest, and clearest panes of glass made from only the finest fixing agents, which at the time meant the glasswort that could only be harvested in its specific and unlovely seaside habitats. Louis XVI wanted to continue his grandfather's tradition of bedecking his every building with as many windows and mirrors as possible, but the coffers couldn't keep up with the rising cost of glasswort-made panes, so he offered a prize of 2,400 livres (about $11,000 in today's money at actual conversion, but more like a year's wages in that era's extreme income inequality) to anyone who could invent a cheap way to make glass-grade potash. One of his court physicians took up the challenge, and although he succeeded, his life only went downhill from there.

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