Egyptian Blue Opal Frit (164)
Copper bearing glass that reacts to sulfur bearing glasses, Reactive Cloud (009), Reactive Red (1019) and Reactive Ice (1009). Opalizes upon firing. May contain thin threads of color variation. At a full fuse, Egyptian Blue Opalescent has the potential to deposit trace amounts of copper on the surface of the kilnshelf. These deposits may react with sulfur-bearing glasses in subsequent firings. Processes that require greater heatwork, such as pattern or flow bar techniques, can also lead to copper deposits. Such deposits may not be visible and can react even when the shelf has been properly scraped and reprimed or, alternatively, when used ThinFire has been removed and new ThinFire is applied. This type of contamination is impermanent and may be burned out/fired out over the course of subsequent firings. A contaminated shelf can be fired with glasses—other than sulfur-bearing glasses—and no reaction will take place. In our studios, we've observed the greatest contamination in subsequent firings with sulfur-bearing French Vanilla Opalescent (000137) and Spring Green Opalescent (000126). For a burnout firing, we recommend a rate of 300°F/hr to 1525, with a hold of 1:00.
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