A practical treatise on the manufacture of colors for painting : comprising the origin, definition, and classification of colors; the treatment of the raw materials .. etc. . se the pressure of the muller, and to diminishthe velocity of the rotation of the cylinder. 3. Too great a velocity is prejudicial to the bright-ness of delicate colors, especially when the stonesbecome hot. The inventor also recommends a process for pre-paring the bladders for oil colors. A small wooden MILL FOR DRY mDIGO. 607 peg is inserted in the neck of the bladder, and a stringis tied upon it. By removing the peg an
A practical treatise on the manufacture of colors for painting : comprising the origin, definition, and classification of colors; the treatment of the raw materials .. etc. . se the pressure of the muller, and to diminishthe velocity of the rotation of the cylinder. 3. Too great a velocity is prejudicial to the bright-ness of delicate colors, especially when the stonesbecome hot. The inventor also recommends a process for pre-paring the bladders for oil colors. A small wooden MILL FOR DRY mDIGO. 607 peg is inserted in the neck of the bladder, and a stringis tied upon it. By removing the peg and pressingthe bladder, the color runs out upon the pallet. Itwill be still better to tie the bladder upon a quill, withthe point on top, because by cutting it, the color maybe squeezed out. The drying of the color remainingin the bladder will be prevented by plugging thequill with a small wooden pin. This method iscleaner and more economical than that of perforatingthe bladders with a knife blade. Mill for dry indigo. Fig. 63 represents an ordinary mortar L, made ofmarble or of some other hard stone, in which revolvesa muller M, which is pear-shaped. Fig. 63. Fig. Its axis revolves at N, upon two pieces of oakwood fastened to the wall Q. Pins are put in o o,in order to retain the axis in its jDlace. P is the 608 APPENDIX. crank handle. R is a movable weight, which isadded when it is desired to increase the weight ofthe muller. Fig. 64 represents the muller and its axis removedfrom the mortar. The lower curve of the mullershould correspond with that of the mortar. S is adeep groove in the muller. A certain quantity of coarsely broken indigo isput into the mortar, and the rotary motion of themuller causes the pieces to fall into the groove, andto become finely ground. The operation will berendered more easy, if the lower part of the groovebe made slightly wider. By covering the mortar with two pieces of woodmeeting in the middle, and having a hole for thepassage of the axis,
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherphila, bookyear1874
