. Transactions of the Society of Motion Picture Engineers (1921) . ger-ating rooms and left until it has set to a stifif jelly. This jelly isthen put through a machine very much like a big meat chopper, thewhole machine being made of silver or pure nickel. The emulsion iscut up into fine worm-like shreds and washed in repeated changesof water in order to free it from the products of chemical reactionand the excess halide salts. When washing is complete the shredsare drained and melted up ready for coating or spreading upon the 136 celluloid base. Just previous to coating the emulsion is passed
. Transactions of the Society of Motion Picture Engineers (1921) . ger-ating rooms and left until it has set to a stifif jelly. This jelly isthen put through a machine very much like a big meat chopper, thewhole machine being made of silver or pure nickel. The emulsion iscut up into fine worm-like shreds and washed in repeated changesof water in order to free it from the products of chemical reactionand the excess halide salts. When washing is complete the shredsare drained and melted up ready for coating or spreading upon the 136 celluloid base. Just previous to coating the emulsion is passedthrough a vacuum filter to remove dirt and other foreign substances,for the emulsion for moving picture work must be free from dustand dirt. The machines for coating are highly specialized units, each ma-chine being set in a long alley into which only washed and condi-tioned air can enter; there are means of varying the temperature andcontrolling the humidity of the air throughout the length of thealley. A coating machine head is shown diagramatically in Fig, 1,. rig. 1—Diagrammatic Sketch of Coating Machine Head the passage of the stock through the machine being plainly emulsion is held in a water-jacketed pan, and means are pro-vided for maintaining a constant level and is transferred to the cellu-loid either by dipping or beading. In dipping the celluloid a tensionroll comes around, which just touches the surface of the emulsionin the pan. It is transferred by a second beading roll by capillaryattraction. After the celluloid has received the emulsion the stockrises over a chill roll and is carried by a suction apron to the firstlifting stick, then carried on down the alley in festoons. During itspassage down the alley the necessary drying and curing takes placeand the stock winds up at the far end of the alley ready for trans-ference to the slitting machines which cut it into niotion picturewidth. It will be readily understood that a large plant devoted to thepro
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