When reheating glazes, I like to do so in short and high bursts in the microwave. I heat for 30 seconds on High (100%) and stir the glaze with a spoon, then heat again. I like to bring the glaze to a fairly high temperature of around 60–70°C (140–158°F), which will make the glaze become nice and shiny. I then leave the glaze at room temperature, stirring intermittently, until the temperature drops to 35–40°C (95–104°F) before glazing the cake. I use a digital thermometer to check the temperature accurately. If you use a glaze that is too hot it can melt the cake and run off quickly, leaving a very thin finish.