Glass failure analysis expert performs a failure analysis of cracked glass swimming pool tiles. The photo on the upper left is of one of the cracked tiles. This is a clear glass tile made from re-cycled glass. The failure analysis, photo on the upper right, shows that these tiles were cracking from the backside of the tile. In this particular pool, only the clear glass tiles cracked. The colored tiles in the same pool did not crack. Light transmission measurements showed that the clear tiles transmitted more infra red light. The present hypothesis is that the infra red light passed through the clear tiles and preferrentially heated the mortar on the tile backside. The heating created tensile stresses and cracking on the tile backsides. The heating was more intense for the clear tiles; this is why they cracked.