Second, the process for recycling the glass bottles has developed to enable the label to be removed prior to the heating phase. The recycling process for glass bottles involves smashing the glass into particles and then screening the pieces. The screens remove metal and paper. Fibre is considered a glass contaminant and will cause impurities in the end product if it is not removed. These glass products all have different composition and therefore different melting points, making it impossible to make glass bottles without imperfections.
Broken glass is a handling hazard for the recycling truck operator.
As well, once glass is broken it is very difficult to determine what type of glass it is and therefore it could be a contaminant. Most window envelopes are made out of water soluble paper fibre instead of the plastic that was once used. It is preferable but not mandatory. During the paper recycling process, the pulp passes through numerous screens to remove staples and other contaminants. You should remove large metal fasteners from corrugated cardboard boxes.