Crucible Glazing

Before using a new crucible made of graphite, silicon carbide or clay, the interior of the crucible should be glazed using a saturated solution of Boric Acid and Methyl Alcohol. The solution should be painted on the crucible wherever the molten metal will come in contact with the crucible, and the complete upper lip of the crucible. The purpose is to prevent the composition material of the crucible from sloughing off into the molten mass and being carried into the casting, and secondly, to extend the useful life of the crucible.

The crucible should be heated until the glaze is clearly evident completely covering the surfaces to be glazed. If after the heating areas of the crucible do not show a shiney surface (glaze), reapply more of the solution and reheat until glaze temperature has been reached again.

When using an Electromelt, once the interior has been well glazed and the crucible used in a pour, the upper area of the crucible should be recoated with the glaze each time the crucible is used again. Coat the crucible prior to adding metal, and as the furnace raises the temperature of the metal added, it will simultaneously reglaze the crucible before the metal becomes molten.

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