The Institute of Scrap Recycling Industries, Inc. (ISRI) publishes specifications and practices for container glass and flat glass cullet purchased and sold in the United States and Canada. These glass cullet specifications are divided into two categories: unprocessed and processed cullet.
Unprocessed container cullet is defined as broken or whole scrap glass. Specifications for unprocessed cullet are listed for flint (clear), amber (brown), and green (emerald). This material is generated by a recycler and must be processed before it is furnace ready.
Processed container cullet is defined as crushed and whole contaminant-free scrap container glass that is furnace ready. The size of the cullet can vary from whole glass containers to minus-100 mesh. The ideal material size is generally 3/8 inch to 3/4 inch with a 10 percent maximum of fine particles. Material size is based on the buyer and seller’s agreement. Container cullet cannot contain ferrous and nonferrous metals, ceramics, or other glass (e.g., plate window, heat-resistant, or lead-based glass). The specifications also describe the amount of cullet color segregation allowed. For example, clear glass cullet must not contain more than 5 percent colored cullet.
Beneficiated glass is cullet that has been sorted, cleaned, crushed, sized, and therefore is “furnace-ready” for sale to bottle or fiberglass manufacturers. It must be processed to ASTM standards for using recycled glass in containers, or to a modified standard mutually agreed to by the beneficiator and its customer.