Some glassmakers may use 60% or more for coloured glass.
In the production of extra white (almost transparent) glasses, glassmakers use as little slag as possible (10%), both waste and scrap from manufacturing, to avoid impurities present in the recycled material.
It is also possible to produce new containers from slag alone, but precautions are necessary to ensure a certain homogeneity of the molten glass.
An already recycled glass container can be recycled indefinitely.
The original mineral does not change when the melting process is repeated: it changes its shape, consolidates by cooling and can be reused.