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find them with ease in the canvas of the Marìa Magdalena which we are now studying.

ULTRA VIOLET RAY TEST:

The ultra violet ray test of the painting of Marìa Magdalena was made by means of a Quartz Lamp with electronic discharge at high tension and automatic wiring.  Said lamp or apparatus throws an immense variety of visible and invisible rays which, with the exception of those specifically called ultra-violet, are intercepted by means of a special screen.  The rays which pass through said screen, are the ultra-violet ones, practically invisible, which have the property of giving certain substances a phosphorescent aspect when examined in a dark chamber, as for instances applies to varnishes which show a rather luminous phosphorescence, while the aglutinations and pigments reveal feebler luminosities of various colors.

The most important facts that can be ascertained by means of ultra-violet ray tests, in a painting, are the following ones: 

a) Ascertainment of the various materials used in the painting. (Matters which look the same under solar light, may look absolutely different under ultra-violet rays for instance, white lead shows light grey, and zinc white shows up yellowish);
b) Detection of impastings, retouches;
c) Detection of finger prints;
d) Detection of signatures and legends, invisible under solar light, and other matters of secondary importance.