Calendering
Calendering uses a very large pair of heated rollers to physically squeeze the needle felt as it is passed through the gap between them.
Coatings and Impregnations
A wide range of chemical treatments are available for the enhancement of felt properties.
Heat Setting
When fibers are manufactured they invariably have a residual tendency to shrink in length when heated substantially. After these raw materials are converted to filter felts, they need to be heat stabilized to ensure that any shrinkage in the final application is minimized.
Singeing
The singeing process involves rapidly moving the felt through a gas flame which then either burns off the protruding fibers or causes them to shrivel up into tight balls of polymer.