Superfest glass, also called CV-Glas or Ceverit and no longer in production, is known for being extremely durable. It was made with borosilicate glass, chemically strengthened to enhance durability. The process involves submerging the finished glass shape into a molten salt bath (such as potassium nitrate, KNO3) at high temperature. Through a process of ion exchange, smaller ions (sodium, Na) in the substrate are replaced with large ions (potassium, K) from the salt bath. This 'stuffing' creates high levels of compression in the surface. The hard surface provides enhanced resistance to flexural breakage, scratching and thermal shocks. Real-life performance is highly dependent on flaws in the glass. In the case of chemically strengthened glass, damage has to penetrate through the pre-compressed layer to cause failure.

NSB Class 71 train, built by Adtranz Strømmen, featuring spot welded stainless steel body shell and strengthened glass