Ground coat enamel frit are made from a frit based on low melting temperature (2000 to 2500°F) borosilicate glasses. After the glass raw materials are melted (generally in recuperative furnaces) at rates ranging from 5 to 50 tons per day, rapid quenching is used to shatter the resultant glass into small particles. Further particle size reduction is achieved by grinding. The coating is applied using wet suspension or dry electrostatic powder processes, and is then heated to about 1500°F to produce chemical bonding with the metal substrate.
Producers can achieve many colors and formulations in small melting units. Due to the low melting temperatures, the average dwell time is only a few hours. Since the ground coat enamel frit is melted a second time with the metal substrate, seeds in the glass are not a concern as long as the melt is homogenized and all raw material reactions are completed.
Pre-milled ground coat enamel frits now allow enamelers to custom blend their own enamel formulations without using costly milling equipment. The enameler can blend the exact amount required for the job, eliminating waste. Blends can be made almost “just in time,” eliminating the need for a large wet enamel inventory.
Many enamel frit manufacturers have switched from air/gas to oxygen/gas combustion systems to lower their emissions, and this trend is expected to continue. Smelters have become more automated, and larger capacities are being used as product volumes increase through the increased standardization of frits.
Enamel frit manufacturers continue to research coatings to address new applications. For instance, unique appearance characteristics are under development, including metallic lusters to simulate copper metal or stainless steel appearances. Refinements in ground coat enamel frit products are also being made to achieve “easy to clean” oven coatings, as well as infrared reflectivity for faster cooking. In addition, hybrid coatings are being investigated to take advantage of properties provided by both porcelain enamel and organic coatings.
This article comes from ceramicindustry edit released