Acid Polishing of Lead Crystal Glass

Abstract

The industrial partner manufactures high quality lead crystal glassware. The cutting of decorative features in the glass damages the surface and the cuts are optically opaque; to restore transparency, the glass is polished in a solution of hydrofluoric (HF) and sulphuric acid (H2 SO4 .) The polishing process comprises three stages:
1. immersion in a polishing tank containing acid;
2. rinsing in a tank containing water; and
3. settlement of the solid reaction products in a settlement tank.
The manufacturer hopes to optimise its polishing process to
• minimise the health/environmental impact of the process;
• maximise throughput;
• maintain the sharpness of the cut edges while still polishing to an acceptable level of transparency.

The study group was asked to focus on modelling three aspects of the process:
• the chemical reactions involved in the etching at the glass-acid solution interface;
• the removal of reaction products in the settlement tank;
• flow within the polishing tank.