In the lost-wax casting process, investing means coating or encasing a wax or plastic pattern in a refractory material. The slurry hardens into a solid shell or block around the pattern. Once the mold is fully cured, the internal pattern is melted or burned out to leave a precise cavity for molten metal.
Heard on the job
Make sure you vacuum the slurry well before you invest the wax trees to pull out any trapped air bubbles.
Insider tip
A poor vacuum during investing leaves microscopic air bubbles against the wax, which turn into solid metal nodules on the final casting.