<P> In 2000, some manufacturers began offering high power quartz halogen bulbs to their convection microwave models, marketing them under names such as "Speedcook", "Advantium", "Lightwave" and "Optimawave" to emphasize their ability to cook food rapidly and with good browning . The bulbs heat the food's surface with infrared (IR) radiation, browning surfaces as in a conventional oven . The food browns while also being heated by the microwave radiation and heated through conduction through contact with heated air . The IR energy which is delivered to the outer surface of food by the lamps is sufficient to initiate browning caramelization in foods primarily made up of carbohydrates and Maillard reactions in foods primarily made up of protein . These reactions in food produce a texture and taste similar to that typically expected of conventional oven cooking rather than the bland boiled and steamed taste that microwave - only cooking tends to create . </P> <P> In order to aid browning, sometimes an accessory browning tray is used, usually composed of glass or porcelain . It makes food crisp by oxidizing the top layer until it turns brown . Ordinary plastic cookware is unsuitable for this purpose because it could melt . </P> <P> Frozen dinners, pies, and microwave popcorn bags often contain a susceptor made from thin aluminium film in the packaging or included on a small paper tray . The metal film absorbs microwave energy efficiently and consequently becomes extremely hot and radiates in the infrared, concentrating the heating of oil for popcorn or even browning surfaces of frozen foods . Heating packages or trays containing susceptors are designed for a single use and are then discarded as waste . </P> <P> Some current plastic containers and food wraps are specifically designed to resist radiation from microwaves . Products may use the term "microwave safe", may carry a microwave symbol (three lines of waves, one above the other) or simply provide instructions for proper microwave use . Any of these is an indication that a product is suitable for microwaving when used in accordance with the directions provided . </P>

When were microwaves first sold in the uk