Micro-porosity is a recurring defect in gold casting, especially in high-carat alloys. It manifests as tiny microscopic voids that compromise the structural integrity and surface finish of the pieces. For jewelers and precision workshops, understanding its origin and how to mitigate it is key to avoiding rejections and economic losses in production.
Causes and technical solutions in the casting process 🔧
Micro-porosity usually originates from trapped gases during melting or from uneven solidification of the metal. Factors such as excessive temperature, mold filling speed, or moisture in the investment material are common triggers. To reduce it, it is recommended to use controlled atmospheres with inert gas, degas the melt with borax or activated carbon, and optimize the sprue channels in lost wax casting. Slow and uniform cooling also helps gases escape before the metal solidifies.
The drama of invisible little holes that ruin your polishing 👻
Those microscopic pores are like the ghosts of jewelry: you don't see them until it's too late. You spend hours polishing a piece and, suddenly, a tiny crater appears that forces you to fill it with solder and start over. In the end, you suspect the gold, instead of solidifying, decided to foam. The worst part is that the customer always finds the only pore you missed, right in the most visible area.