The glass cullet is passed through a magnetic field, where metal contaminants like metal bottle caps are removed from the glass. Other contaminants like paper and plastic are picked up manually or through an automated process.
Ceramic contaminants are removed from the glass cullet via a process known as fine sizing. The finely ground glass cullet is passed through various screens, leaving behind ceramic residues.
If, however, ceramic contaminants do pass through the various screens together with the glass cullet, the quality of the recycled glass will be affected. Ceramic contaminants in glass can lead to structural defects.
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