Bridgman seal
A Bridgman seal, named after Percy Williams Bridgman
Percy Williams Bridgman
Percy Williams Bridgman was an American physicist who won the 1946 Nobel Prize in Physics for his work on the physics of high pressures. He also wrote extensively on the scientific method and on other aspects of the philosophy of science.- Biography :Bridgman entered Harvard University in 1900,...

, seals a high pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 volume by the use of a three part mechanism. A viscous material such as rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

, copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 or soap stone is set so that it stretches longitudinally against a hard steel ring, followed by a softer steel ring and horizontally against a steel piston. This arrangement ensured that higher pressures created tighter seals.

This seal allowed for pressure increases from 400 Mpa to 40,000 Mpa. These are typical pressures expected in the Earth's internal structure. For Bridgman a whole universe of possibility had opened. Everything he squeezed did something interesting and unexpected. Water froze into strange phases. Salts changed colour. Conductivities changed unpredictably. A new science world became explorable.
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