= High-pressure experimental metrology
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.<General Survey of Certain Results in the Field of High-Pressure Physics by Percy Williams Bridgman>[General survey of certain results in the field of high-pressure physics, delivered 11 December 1946, p. 53 opening and Figure 1 caption]{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>.
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