Source: The Bethlehem Oil Mill 1745-1934 German Technology in Early Pennsylvania
Authors: Carter Litchfield, Hans-Joachim Finke, Stephen G. Young and Karen Zerbe Huetter
Published and distributed by Olearius Editions
Following the tradition of their Germanic homelands, the Moravians utilized hemp as a major fiber for making strong, durable cloth. Hemp fiber was spun into hempen yarn and then woven into hempen cloth.30 To make the coarse hemp fibers soft and pliable enough for normal spinning and weaving, it was necessary to hammer, stamp, or roll them to break down their natural resinous coating and to subdivide the fibers. This softening process was accomplished using machinery at the Bethlehem oil mill.
The Moravian process for preparing spinnable fiber from the hemp plant required six steps (figure 36) and closely resembled the preparation of linen fiber from flax.31 Hemp fibers occur only in the outer layer of the stem of the plant and must first be separated from the other plant tissues. To accomplish this, the freshly pulled hemp stalks were "retted," i.e., laid on the ground and exposed to the weather for 3 to 6 weeks until the nonfibrous portion of the stem started to rot and decompose.32 Next the hemp stalks were dried by heating them over a fire.33 The dry stalks were then crushed using a hemp brake, which resembled a common flax brake but was larger. This shattered the friable, rotted portion of the stalk so that most of it fell away from the fibers. The remaining bits of woody material were removed by scutching, i.e., by scraping the fibers with a wooden knife. To soften the fibers for spinning, they were repeatedly hammered, stamped, or rolled with a stone. Finally, the fibers were pulled through a series of hackles, combs with iron teeth, to align the fibers and to remove the shorter lengths.34
Although spinnable hemp could be produced by hand labor alone, softening the fibers by pounding them with a hammer was extremely arduous work. At Bethlehem this softening step was mechanized using water-powered equipment of traditional Germanic design.35 Hemp stamping mills were built in the 1752 and the 1765 oil mill buildings, and in 1767-1768 a hemp roller mill was added. Many mechanical details of the two machines at the 1765 oil mill have survived so that we can clearly understand how they operated.
The hemp stamping equipment at the 1765 Bethlehem oil mill is depicted in the 1766 Herrnhut drawings (figures 29 & 30) (1765: PLANS SHOWING HEMP STAMPERS); a simplified elevation view has been drawn in figure37. It was a stamping mill very similar in size and design to the oilseed mill installation, except for the different shapes of the stamping heads and trough. Hemp fiber (after scutching) was placed in the stamping trough, the stampers were engaged with the lifting cams36 as shown in figure 33, and the heavy stamping poles were repeatedly lifted and allowed to fall onto the hemp. After the hemp had been sufficiently softened, the stampers were disengaged, the hemp was removed from the trough, and it was ready for the final hackling step.
The stamping heads shown in the 1766 Herrnhut drawings (figure 30) appear to be stepped like those used in fulling mills.37 Although there is no confirming side view, this interpretation seems likely for two other reasons. This was a dual purpose mill designed to full leather as well as to stamp hemp. Moreover, before the 1752 hemp stamping mill was built, the Moravians had used their cloth fulling mill to stamp hemp.38 a conjectural cross section of the hemp stamping head and trough (figure 38) shows how the stepped head could have rotated the fiber with each blow because of the curved sides of the trough, the same as in a fulling mill.39
In 1767-1768 another type of hemp softening machinery was installed at the oil mill.2 This was a hemp roller mill located on the second floor of the west side of the building in the vacant area shown in the 1766 Herrnhut drawings (figure 28).40 The description of materials purchased for constructing this new hemp mill strongly suggests that it consisted of a stone that rolled around a circular bed.41 Similar hemp mills have been reported in early America,42 and one has survived intact at a German museum (figure 39) (1767: HEMP ROLLER MILL STONE).43
To soften hemp on such a roller mill, bundles of scutched fiber were placed on a circular bed, and a heavy stone shaped like a truncated cone (figure 63) was rolled over the fibers until they were sufficiently soft and pliable. An iron axle through the center of the stone was attached to a vertical drive shaft at the center of the bed. At the Bethlehem installation the hemp roller mill was probably driven from below by a gear train that included the large face gear at the end of the west waterwheel shaft (figure 31). An iron collar around the edge of the bed kept the fiber in the pathway of the revolving stone. From time to time during the run, the hemp was turned and shaken to assure that all parts were evenly treated. At the end of the run, the roller mill was stopped, and the softened hemp was removed and taken for the final hackling. Similar hemp mills in Europe reportedly could soften two hundred pounds (91 kg) of hemp in eight hours. 45
The fact that the Moravians built a second type of hemp softening mill in 1767-1768, only two years after completing the 1765 machinery, implies that their 1765 hemp stamping mill did not yield satisfactory results. In their 1765 advertisement (figure 15) they had claimed a distinct advantage for their stamping mill: "The Hemp is not rubbed 46 with a Pumicestone [roller stone] in the common Way, that being attended with many Dangers; but it is stamped in a particular Manner and becomes pliabler and fitter than with the Stone." Apparently this claim was not realized. Their customers may have been quite satisfied with the "common' hemp roller mill, or perhaps the roller mill processed hemp with less manpower and thus at less cost. 47
Hemp usually was processed at the mill during the late fall and winter months. In 1766-1767 when only the stamping mill was used, 6242 pounds (2328 kg) of hemp were softened. With both hemp mills in operation, the Bethlehem oil mill processed 28,502 pounds (10,631 kg) of hemp in 1770-1771 and 41,403 pounds (15,433 kg) in 1771-1772.48 Hemp softening continued at least through 1792.49 No mention of the process after that date has been found.
Reprinted with the gracious permission of the authors and the
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