Hollander beater

The Hollander beater is an industrial machine used in papermaking for preparing pulp. It consists of an oval tank with a heavy, bladed roll that rotates against a bedplate. This machine mechanically pounds and squeezes cellulose fibers, causing them to swell and become flexible. The beating action separates and frays the fibers, creating hairlike fibrils. This process reduces drainage rates, leading to denser paper with higher tensile strength and lower porosity. The Hollander beater is also effective for mixing in additives like sizing, fillers, and dyes, and can be used for washing the pulp. While still used in specialty paper mills, larger operations have largely replaced it with continuous refiners.12