The phenomenon of curling, agglomeration and detachment of the enamel layer from the body is generally called enamel shrinkage for two reasons: one is dust in the enamel and the shrinkage of the enamel itself. Some glazes, especially those containing tin oxide , shrink and become larger lumps if the glaze is applied too thickly or to a dirty surface. The remedy is to remove the dust on the bare surface with a damp sponge. Set up a dust removal room to prevent dust from falling out of the gaps. If the glaze needs to be properly thickened, a small amount (3%) of bentonite can be added to the glaze. Underglaze paint is prone to glaze shrinkage defects because the colored material of the underglaze paint resembles the dust left under the glaze. In response to this situation, a small amount of enamel slurry or a small amount of gum arabic can be mixed into the enamel powder.
The second main reason is that the content of plastic components in the enamel is too high, so during the drying time the enamel layer shrinks too much, causing fine cracks and cracking the enamel surface. Heaps of icing and lumps form easily during the cooking process, but they can't melt evenly and cover the green body. This error often occurs with cookie-baked blanks. Therefore, this type of nail polish is basically suitable for undefeated green bodies. Some non-plastic raw materials such as calcined clay and kaolin and calcite can be suitably added to the glaze to suit use on scale fired ingots. The amount of non-plastic raw material added is equal to minus a certain amount of plastic raw material. Lightly rubbing the dried icing with your fingers to smooth the icing can also remove some cracks in the icing. If the surface of the glaze is not dry enough to meet the requirements, too rapid heating will also easily lead to glaze stacking defects.