Why can’t I put broken drinking glasses, window glass or mirrors in the recycling bin?

Kitchenware, mirrors and windows are made of heat-strengthened material and melt at a higher temperature than glass used for jars and bottles. This means that these materials will not melt during the recycling process and cause contamination of the finished product (5g of this material in 1 ton of glass is enough to contaminate the whole load).  more