Fine powder can take a long time to de-aerate by settling and will resist direct compaction by deforming easily and re-expanding when compacted unless sufficient air has left the voids for the tensile strength of the compaction to exceed the separating stress due to the void pressure.

Carman Industries make a rotary vacuum densifier that claims Kaolin clay is densified from an initial bulk density of 15 PCF to a final bulk density of 27 PCF where it is discharged into a supersack operation that results in more product being shipped per sack while creating a more stable sack with the removal of the air from between the particles.

Roller compactors with porous rollers are also used to densify powders to a greater degree, I believe made by Babcocks. ■