Good hardening makes Duralex stronger but also durable - this is the tempering process. It consists of shock cooling by cold air ventilation over the Verrier product which has previously been at a temperature of approximately 700°C. This treatment creates controlled pressures in the glass which improve most of its physical qualities: resistance to mechanical stress (bending, shocks) and thermal shocks. 2.5times stronger than an annealed glass product, and able to endure a thermal shock of 130°C, our products can easily be used in anything from freezers to microwaves. Directions for use:–Wash before use–Do not use in the oven. - Do not expose products to flames. - Do not put expose the product to sudden changes in temperature of over 130°C–Do not use a damaged or chipped product (risk to the user). - Avoid scratching the surface of products.