How do you distinguish overglaze, in-glaze and underglaze decoration?

Please verify the following points and require itemized written supplier responses:（ceramic tableware glaze colors） Overglaze decoration sits above the glaze and may feel slightly raised; in-glaze decoration melts into the glaze; underglaze decoration lies beneath the glaze and usually feels smooth. Prefer plain white, underglaze or in-glaze for food-contact inner surfaces and require lead and cadmium reports for overglaze items. Define capacity, accuracy, materials and operating environment before requesting quotes on a uniform basis. Request specification sheets, test reports, certificates, maintenance manuals and spare-part lists. During acceptance, verify appearance, dimensions, functions, safety protection and packaging, and keep test records. Do not compare unit price alone; include customization, freight, spare parts, after-sales support and downtime risk. Keep written records of inquiries, confirmations, FAT, acceptance and warranty commitments.