Aventurin glazes Ga-Series are leadless glazes based on frits with a high content of alkaline oxides. Firing temperatures are between 960-1080 °C, but when fired hotter than 1000 °C they run down. The glazes are oversaturated by the iron oxide which crystallize during the cooling and create a little impressive shiny crystals. Glazes are suitable for the dinnerware because they content no lead. However as a rule they are used for decorative ceramics regarding to their higher CTE alfa > 90-120 x 10-7 (K-1), they craze much and after a longer exposition in the water a salt blooming rises. These glazes are very unreliable regarding to reproducibility. It is important to hold firing conditions, thicker glaze layer, firing horizontally and enough long time for the cooling and the proper crystallisation. On the vertical surfaces they run down and in the lower thick layer crystals created. Good results can be obtained by overglazing of the white glaze, for example Dw 153 91.