A Guangzhou personal care manufacturer had been running a stable conditioner line for three years when a new batch of Fatty Alcohol Polyether arrived from a domestic supplier they had recently added as a second source. On paper the material looked fine — assay in range, HLB within spec, color acceptable. But within two weeks of filling, translucent bottles started showing separation at the bottom. The plant’s formulation chemist eventually traced it to an unexpected narrowing of the ethylene oxide chain distribution in the new batch. The previous supplier had been producing material with a broader EO profile that happened to interact favorably with the silicone emulsion droplets in the formula; the new supplier’s tighter distribution broke that coincidental stability. Three years of cumulative formula development — one undocumented assumption baked deep into it.