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. 2.5 times 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: â Wash before use â 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 â Do not use a damaged or chipped product (risk to the user). - Avoid scratching the surface of products.