Many assume yellow MgO bottoms are "high purity" and white ones "low quality." In reality, color reflects sintering conditions and light reflection-not composition. Yellow bottoms are made from 99% pure seawater- or mineral-derived MgO, sintered at 160°C to form dense crystalline structures with thermal conductivity up to 35 W/m·K, efficiently transferring heat from the wire to the sheath and preventing hot spots. White bottoms are typically 39% MgO + alumina composites, rated only to 8°C with thermal conductivity below 60 W/m·K-suitable for low-temp sealing machines, not core mold heating. In injection molds, using white bottoms at 500°C+ causes high thermal resistance, delaying core temperature response and leading to inconsistent cooling, flash, or sink marks. The high thermal conductivity of 99% bottoms ensures ±5°C control accuracy-essential for precision molding. Always request material certification, not rely on color.
