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High-pressure experimental metrology connects three tasks: producing pressure, retaining it without leakage, and assigning a calibrated value to the pressure experienced by a sample. A large applied force alone establishes none of the last two. The useful result is a reproducible material property at specified pressure, temperature and stress conditions, with stated measurement uncertainty.

Percy Williams Bridgman identified leakage as an earlier experimental limit. His 1946 lecture describes packing that tightens as pressure rises, ultimately leaving vessel strength as a limit.^[ref]

The Bridgman unsupported-area seal turns the very pressure that would drive a leak into an extra seating force. Its appeal is a feedback between load and sealing, rather than an assumption of perfectly fitted rigid surfaces. The piston-cylinder pressure apparatus below explains that feedback; pressure calibration then separates the applied load from the sample's inferred pressure.

Awarded to Percy Williams Bridgman for high-pressure apparatus and discoveries made with it. The pressure article develops the associated measurement problems.^[ref]

Percy Williams Bridgman developed apparatus that made very high pressures useful as a controlled experimental variable. A pressure-assisted seal tightens as the load increases, helping contain conditions that would defeat a simple fixed gasket. Measuring changes of volume, phases and other properties under pressure reveals how strongly compressed matter differs from its ordinary state. His account connects the mechanical design of the pressure vessel with the reliability and range of the resulting physical measurements.^[ref]

A physicist.^[ref]