One of the most ambitious efforts at industrial development pursued by the French administration during the 18th century was a vast project to improve the quality of spun silk to free the kingdom of France from its dependence on foreign suppliers. This article examines the outcome of this plan by analyzing the relationship between technical innovation and profits. Profit is understood in both its discursive and material dimensions. On the one hand, the article shows how economic actors at the time conceived of the relationship between profit and technology in distinct ways. On the other hand, it explores the varying capacities of different technologies to generate profits. This approach allows for the resolution of an important puzzle about the mechanisation of silk spinning in France by shedding new light on the historical relationship between technical and economic dynamics and it offers important insights on political economy as an emerging science of wealth.