Volume 14, Number 3, Sept 1992, p.6

Building a Medieval Papermill

by Jack C. Thompson

At 3:00 pm, 19 July 1991, a new tool for the study of early European papermaking was put into operation in the hills near Santa, Idaho. As an adjunct to the annual workshop on the technology of the medieval book which they teach, Jack Thompson and Jim Croft, assisted by Lou Flannery, Ed Gordon, Sam Thompson, Brian Griswold, Nickle Romanuck, Allan Thenen, Stephen Wilson, and Ed Clark, built a three-hammer stamp mill to produce paper pulp. The mill, designed by Thompson, consists of a 4-foot- diameter water wheel, a camshaft, and three hammers, operating in a concrete tub. The power comes from a pond on Croft's land. A siphon delivers the water to the wheel, which operates at approximately 20 rpm; there are two cams per hammer, delivering a total of 120 blows per minute on the rags in the tub.

The first set of hammers have sharp teeth to reduce the rags to thread. The second set of hammers have blunt teeth, to reduce the threads to fiber. The third, and last, set of hammers have smooth faces, to hydrate the fibers prior to sheet forming.

The mill site will be extended to accommodate 6 additional hammers and two more tubs. This will permit an increase in production because all three stages of beating will be conducted at the same time.

The reason for building the mill was to explore the relationships between fiber and the machinery which has reduced fiber to pulp. Thompson has begun designing a hollander roll which will operate off of the same wheel to help quantify the advantage of a hollander over a stamp mill using the same power source. The goal in 1991 was to bring the concept to operational status; over the next few years, quantitative studies will be conducted using traditional fibers.

Jack C. Thompson
Thompson Conservation Laboratory
7549 N. Fenwick
Portland, OR 97217

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