The 21st of October 1806, Napoleon had decreed the Continental System, a measure taken to deprive England of any contact with the continent. For this reason some products were missing such as Indigo,a sort of blue dye.The government suggested to replace it by the blue starch extracted from woad.A blue dye can be obtained from its leaves. In 1811, the government opened a competition to develop woad cultivation.Nicephore made this commentary :



Woad

“{….}the problem was to extract indigo from woad.We were keenly interested to participate to research the result which was obviously linked to the prosperity of commercial trade and arts.
The research took us a long time but was fruitful from the angle that mostly interested us ; because the samples of this coloring material that we sent from the offices of the sous-prefecture to the Interior Ministry brought us the most willing and flattering encouragements.“
The purpose was to improve the output of the dye production.The Niépce brothers transmitted to the Interior Ministry samples of the dyeing starch that they had managed to extract from the plant leaves,and also a report how they proceeded to obtain this dyeing material .

“ I read with interest M.M.Niépce-Barrault’s observations,that you sent me november 28th on the most convenient time to harvest the woad leaves,and about the means to extract the dyeing starch without the intervention of any precipitating agent ; they are, as you said so well,a new proof of the sagacity and zeal that animate them .Please let them know that I am transmitting those to the commission responsible to examine everything pertaining to the subject and that were done in different locations,and to notify who is more apt to define the theory of the fabrication of indigo-woad, and to improve its practice.“
Answer from the Interior Minister. December 7th 1811

The competion launched by the government did not bring promising results. In 1813, it decided however to rekindle an interest in woad cultivation and indigo extraction by giving Subsidies : three to five francs according to quality and with the condition to produce at least fifty kilograms of indigo per annum. The prefet himself on April 24th 1813 incited the Niépce brothers to start all over again on this project. Woad cultivation restarted in Saint-Loup de Varennes. Fifty-six years later, in 1867 an historian Fouque witnessed: “ {…} Woad-Indigo cultivation,we saw it,has left many traces in what used to the beautiful Niépce property,in Gras,burrough of Saint-Loup de Varennes.The garden of this family property,the fields,even the ditches of the main road,spreading on many kilometers have woad plants {…} that naturally reproduce without any cultivation for more than half a century.“


The year 1812 saw the decline of the Empire.It collapsed putting an end to the Continental System. Woad cultivation decame useless.