Part I of a series on "Toile de Soie," a group of medium-weight taffeta fabrics woven from spun silk (and sometimes raw silk) that wash well without shrinking. It defines the term and explains why washability suits modern sportswear, blouses and shirtings. It then traces the French version, including its use as airplane cloth in World War I, and gives a construction table for Petite Reine, Toile Deauville and Forta Crepe. It closes with finishing notes and a Lever Brothers washability test, and previews the next installment on American versions.