Bourne Archive: Muspratt: Bark Mills
http://boar.org.uk/aaiwxw3MusprattL4BarkMill.htm Latest edit 27 Dec 2010
The Bourne Archive
Extracts Concerning Leather, 4: Bark Mills.
The web pages linked from this introduction are from an article on tanning, under the heading ‘Leather’. The original article is presented here in several web pages, respectively dealing; 1, with leather; 2, with tanning materials; 3, Sources of tannin; 4, bark crushing mills; 5, varieties of skin; 6, hide preparation; 7, the common tanning process; 8, finishing processes; 9, fancy and speciality leathers.
Vol. 2. pp. 508-9
To render any of the foregoing materials 1 suitable for the present operations of the tanner, it is necessary to bring them into a minute state of division, in order that by the treatment to which they are subjected, they may the more quickly yield up their tannin. With the exception of the inspissated 2 juices, this condition is gained by grinding or cutting machines which reduce the roots, branches, or barks, to a fine powder. Numerous kinds of mechanical adaptations have been introduced into this department, varying in simplicity from old head-stone rollers 3, to very intricate arrangements. It would require too much space to give even a curt description of these; suffice it then that the principles on which they are constructed may be inferred from the machines described here:—
4 bark-cutting machine, extensively
The chopped bark is then passed to a mill for reducing it still further, and which is shown in Fig. 344. This machine is on the principle of Weldon’s bark-grinding mill, introduced so far back as 1797. In this figure, A is a conical drum of iron on the end of the shaft, D, which forms its axis, inclosed 7 in the cast-iron hopper, B B, where the coarse bark is deposited. This hopper is firmly secured by screws to a flange, which runs all round the framework, v v, as shown at a a. In the top of the exterior is across beam secured by screws, and having a socket in the middle part through which the axis of the drum passes. The lower part of the shaft rests and turns upon a bed, C, upon the stage, T, and regulated so as to have the cone, A, in position, by the side of the bottom screws, a’ a’ and b. The inner face of the hopper, B, which is in close contact with the revolving cone, is, like the latter, serrated or grooved, so that the bark passing down is more minutely sundered. Fig. 345 shows the position of the two cutting surfaces with respect to one another. The central drum makes twenty-five revolutions per minute, and in the course of twenty-four hours grinds about eight thousand six hundred pounds of bark. The cutting machine already described is capable of supplying three grinding mills.
mill, very much used in
Next Page: Varieties of Skin.
3. ^ This would be a cheaply set up answer to the need. A worn-out runner stone from a corn mill, mounted on an axle pivoted at the centre of a circular stone track and propelled by a horse, would roll over the track, crushing the bark. This design mimics those used for crushing woad and cider apples. An elaborate woad mill is shown on Arthur Young’s page 175. A clearer picture of the mechanism appears in Gatty’s Aunt Judy’s Annual Volume (1883), page 551. The same principle is employed by the olive-crushing mill illustrated here.
7. ^ Inclose is a variant of enclose, derived directly from Latin, while enclose came into English via French. It was once more widely used but now restricted to some legal documents and Acts of Parliament (OED).