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Alloys containing a large percentage of cadmium, zinc, or other low fusing metals are not suitable for enameling as the firing temperature, 1400 F., causes these metals to form oxides o the surface of the stock, before the enamel vitrified, producing holes or chipping. 

Holes are also caused by foreign matter on the surface of the article, or in the enamel. This burns, forming a bubble, which has its surface broken by stoning, leaving a hole

Thos. H O'Brien
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