Correct felt permeability: how open do press felts need to be?

In order to remove water from the sheet in the press section, water must flow easily into the press felt. On the other hand, at the exit of the press nip, water must be kept from flowing back into the sheet. These conflicting demands ensure that felt permeability is always a compromise between good dewatering and re-wetting.

This whitepaper gives background information on felt permeability and describes hands-on tools to determine and optimize the permeability of felts which are running in the machine.