Pinholes and glaze crawling are common ceramic glaze defects, but they appear differently. Pinholes are tiny holes left when gases break through the glaze during firing and the molten glaze does not have enough time to level out. Glaze crawling occurs when the glaze loses adhesion to the body during drying or firing, pulls away, and leaves irregular bare areas.

Common causes include excessive gas release from the body, dust or oil on the bisque surface, uneven or overly thick glaze application, excessive drying shrinkage, and a mismatch between glaze viscosity, surface tension, and the firing curve. Heating too quickly or providing insufficient soaking time may also prevent the glaze from healing after bubbles escape.

During inspection, buyers should evaluate the number of pinholes, the size of exposed areas, and the defect location, especially on plate centers, bowl interiors, and cup rims. For mass production, confirm glaze thickness and firing conditions through samples and retain an approved sample for batch comparison. The exact cause should be assessed together with the ceramic body, glaze formula, application method, and kiln curve.