Permeability (foundry sand)

And in other words, permeability is the property by which we can know the ability of material to transmit fluid/gases.

A decrease in permeability indicates tighter packing and could lead to blows and pinholes.

[1] The absolute permeability number, which has no units, is determined by the rate of flow of air, under standard pressure, through a rammed cylindrical specimen.

DIN standards define the specimen dimensions to be 50 mm in diameter and 50 mm tall,[2] while the American Foundry Society defines it to be two inches in diameter and two inches tall.

formula is PN = (VxH)/PxAxT where American Foundry Society has also released a chart where back pressure (P) from a rammed specimen placed on a permeability meter is correlated with a Permeability number.