The process for improving radiant energy sensitivity of a film base coated with a dispersion of a normally crystalline polyacetylenic compound in a non-solvating liquid which is dried on the film surface; said polyacetylenic compound preferably having at least two conjugated acetylenic linkages and containing from 20 to 60 carbon atoms. The process comprises dispersing said normally crystalline polyacetylenic compound in the non-solvating liquid to a concentration of from about 2 to about 50% polyacetylene crystalline solids and ageing said dispersion by (a) storing at a temperature of between about 0.degree. C. and about 12.degree. C. for a period of from about 1 to about 30 days or (b) freezing said dispersion at a temperature between about -78.degree. C. and about -1.degree. C. for a period of from about 1 to about 75 hours or (c) a combination of the above ageing techniques any or all of which are completed before drying said dispersion on a substrate.