Excerpt from Radium: Radioactive Substances and Aluminum, With Experimental Research of the Same (Classic Reprint)
Experiment 10: I placed crystals of uranous oxid in an aluminum cup and placed the cup on a plate of bone of one mm. Thickness which was on the bare photographic late. In this case the rays have penetrated the aluminum and the bone. Ime 120 hours: Experiment 11: Uranous oxid was placed in an aluminum box which was placed on a photographic plate covered with black paper and after 60 hours it produced a very deep print.
Experiment 12: Uranous oxid was placed in an aluminum box, which was placed on the reverse side of a photographic plate, and after 72 hours it produced a very deep print.