Autochromes Lumière

 

Lamination

Increasing the Transparency through Lamination
Such a system, made up of died starch granules with a carbon filling, was heavily opaque and allowed less than 10% of the incidental light to pass through it. Reading the patents, we can witness some of the technical solutions put in place by Louis Lumière to increase the transparency of the system. The first, which never got beyond the experimental stage, consisted of replacing the black carbon by another, extremely fine, dyed starch. The second solution, retained at the industrial stage, consisted of an operation of lamination that crushed the granules to make them more compact.

Louis Lumière reported that in the course of his research he had once accidentally scratched the starch layer of an Autochrome he was working on with his fingernail. He discovered then, to his surprise, that the plate was more transparent where he had scratched it. He realised then, that in smoothing the granules out in such a manner, he had reduced the overall thickness of the plate and limited the phenomena of light refraction. In other words, the application of pressure compressed the granules against one another and so diminished the empty spaces between them, which were the origin of the parasitic light. This accidental lamination had increased the plate s transparency by 1.5 times. What remained to be determined, however, was a means of submitting the whole plate to such an operation without breaking the glass. Louis Lumière first travelled to Würtemberg, Germany, to try the Hüber press, but this was unsuccessful. He had to come up with a machine that was specifically adapted to the particularities of the Autochrome.

The compression Louis Lumière sought was finally obtained "by means of a cylinder 1.5mm in diameter, in the form of successive tangential rectilinear marks." He had succeeded in reproducing an accidental scratch of his fingernail, through " as he describes it "a series of "successive tangential rectilinear marks."

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