Self Pressurized Rapid Freezing (SPRF)

The Leica EM SPF is based on the principle of Self Pressurized Rapid Freezing (SPRF) (J Microsc 235, 25-35, 2009), a method based on the same principle of Le Chatelier and Braun.

It uses the tendency for water inside the specimen container to expand upon cooling, thereby generating pressure intrinsically instead of using an external hydraulic system.

This pressure is likely to be the result of two processes: ice crystallization and/or supercooling which is the phenomenon that water remains liquid at temperatures well below the melting point of ice.

To achieve pressure adequate for high pressure freezing (2010 bar) at least 50% - (preferably 60%) - of the water needs to be converted to low density ice.