We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
Screen-Plate Patents 479
green was to be as pure a green as possible, the blue being cut off by admixture of yellow. If the mixture thus formed did not give a bright yellow, then a yellow, as near spectrum yellow as possible might be added. Another lot was colored blue. After drying, grinding and sifting, the powders were to be mixed so as to form black. The mass dusted on glass would reflect or transmit all the colors, and the result would be white, in proportion to the purity of the color, and quantity of light transmitted or reflected. This is the first black condition to which reference has already been made, and which was outlined by du Hauron.
The plate thus prepared will show small interstices between the particles and to fill these up the plate was to be heated till the edges met. This plate was to be coated with panchromatic emulsion, or as an alternative it was suggested that an ortho plate be rendered tacky and the colored particles dusted on its surface. The picture might be used as a negative, or be backed with a black surface so as to be viewed by reflected light, as the old ambrotype. The plate might be exposed through the back and the gelatin and silver not acted upon by the pyrogallol developer removed by hot water. It will be gathered from the above that McDonough recognized the process as an additive one, hence his terms "pure red," etc.
The Societe Anonyme des Plaques et Papiers A. Lumiere et ses Fils11 patented a dusting-on method, and the plates are commercially available as the Autochrome plates. The colored elements might be grains of starch, ferments, yeasts, bacilli, pulverized enamels or other transparent powdered matter. These were to be colored red, yellow and blue, then mixed in such proportions that they do not show any appreciable color. The glass was to be rendered tacky and the colored units spread over the same so as not to overlap. Then a second coat of tacky matter was to be used and a second coat of elements, and a varnish was then to be applied. It is pointed out that this varnish must have a refractive index, similar to the color units, so as to prevent diffusion of the light. And the superposition of the above named colors would produce red, green and violet, though where they did not superpose the simple colors would be seen. After the insulating varnish, the emulsion was to be coated and reversion of the negative image was disclosed. This double coating is not disclosed in the U. S. P., but is in the German, and the latter is more specific in that potato starch is taken as the particular grain. Later12 the same inventors found that two superimposed layers of color elements were not actually necessary but that the same results could be obtained by the six colors, red, orange, yellow, green, blue and violet, but also by any given number of colors, distributed in a single layer, and that the powdering might be commenced with large particles and finished up with smaller ones to fill in the interstices, or even black might be used. And it appears13 that the first powdering might be done with two colors and the third applied subsequently. Further patents14 also claimed the perfect continuity of the