Samples of colored silk taken from brittle flags in the National Museum of American History (Washington, DC) have been subjected to light microscopy and scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS). The presence of mordants, weighting materials, and colorants is discussed with reference to the embrittlement of the silk. The ash content of the samples is reported. Micrographs of individual fibers are examined. The correlation between fiber deterioration and elemental composition (as a reflection of possible manufacturing process) is discussed.