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Verneuil process (flame fusing process)

The Verneuil process is a flame fusing process for making synthetic sapphire. It consists of fusing pure, finely powered aluminium oxide at a temperature of more than 2000ÂșC in an oxyhydrogen (oxygen + hydrogen) flame. Like a stalagmite, this liquid drips onto a seedling to gradually form a crystal.

Production may take hours to several days. In order to allow the crystal to grow by superimposing ultrafine layers of fused material, fusing occurs continuously in the same temperature range of the downward flame.

The Verneuil process is used to produce small quantities of color ruby, sapphire and spinel. Most of it is grown as colorless crystal, increasingly as a starting material (crackles) for growing sapphire using other manufacturing processes.