hot take: everyone blames moisture but ignores shear friction. technically, blisters form from horizontal shear (skin layers sliding >20-30kPa) not just hydrostatic pressure.
under the hood: pair double-layer socks (e.g., Injinji toe liner + Darn Tough merino outer) with a vapor barrier liner like DX stuffsack film taped inside your boot tongue. reduces shear by 40-60% per lab tests (friction coeff drops from 0.6 to 0.25 dry-on-dry).
discovery: on my 50mi AT section, taped my heels with 3M Micropore + lube’d with BodyGlide petroleum base. zero blisters vs. 3 last time. math: force = μN, minimize μ with barriers, up N tolerance via padding stack. works on Oboz or Altras.