Thursday, March 24, 2011

Greg Merkel adds some refinement to the discussion of Alabaster v. Calcite.

In my response to the “Calcite versus Alabaster” question the other day, I made an over-simplification to avoid going too deeply into the matter, but Marshall Ketchum quickly (and graciously) brought the inconsistency to my attention, for which I thank him. As Marshall pointed out, Calcite, per se, was not introduced until about 1914, yet most of the Aurene decorated red or green over white glassware was made much earlier.

I’ve found from Carder’s batch notebooks that the white opal glass that was used to make these early pieces was simple named “Aurene White.” (Named “Aurene White” because it was formulated to “work” with Gold Aurene glass; it did NOT contain silver and was NOT a luster glass like Gold and Blue Aurene.) Like the later “Calcite,” Aurene White was an alkali lead borosilicate glass in which calcium phosphate (“bone ash”) and arsenic oxide were added as the “opacifiers.” (Neither glass, however, is fully opaque.) The range in the amounts of these opacifiers in Aurene White and Calcite overlap, but Calcite contains a very small amount of nickel oxide to impart a slightly warmer hue to the glass. So, now that this is all “out on the table,” we should probably refer to these objects as “Gold Aurene decorated Ruby (or Green) over White” rather than “over Calcite” or “over Alabaster” unless we have good reason to believe a specific piece is one of the latter two. Further details will be included in the upcoming book! My apologies for adding to the confusion.

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