As a rule, the term “used glass” is understood to refer to packaging glasses, which are collected for the purpose of recycling. The collected used glass undergoes several sorting processes (manual sorting, magnetic separators and sieves) in glass foundries. During the process, contaminants/impurities are removed. The separate collection of white and coloured glass is necessary because if coloured glass were to be mixed into white glass during production, this would lead to discolouration. (BAWP 2017)
Not as commonly known as the recycling of packaging glass is the collection and recycling of shards of sheet glass. These accumulate wherever sheet glass products are worked with (e.g. in glaziery or carpentry workshops, window factories/recyclers, demolition sites (for buildings), garages and vehicle disassembly plants).
The degree of purity of the collected used glass is crucial for the quality of the recyclate. Apart from product-related foreign substances (e.g. heating wires and films in car windows) used glass must not contain any interfering materials. These include: ceramics, stones, porcelain, building rubble, metals, window putty, synthetic materials, borosilicate glass, glass-ceramics, etc. (bvse-Fachverband Glasrecycling)