News-Antique.com - Sep 30,2009 - Kanawha was one of a handful of companies that made ‘heat sensitive’ amberina glass, back in its heyday in the 1950’s and 1960’s. Amberina is ‘heat sensitive’ glass which shades in color from amber at the bottom to red at the top due to the effects of reheating the top part of the glass before allowing it to cool. Amberina glass was first patented in the USA by Joseph Locke and Edward D. Libby in 1883. Locke was head designer for the Cambridge works of the New England Glass Company, and W. L Libbey and Son were proprietors of this glassworks. Amberina glass contains a precipitate of colloidal gold (as does gold ruby glass), which turns red at the right temperature.
If the effect is reversed and the bottom part of a vessel is reheated rather than the top, the result is called "reverse amberina"- which is red at the bottom and amber at the top. Along with New England Glass, Libbey and Company, and Kanawha, other makers of amberina glass in the US include Hobbs Brockunier and Company, Gillinder & Sons, Fenton, Blenko, and Boyd’s Crystal Art Glass.
Kanawha made much of their amberina as crackle glass, another one of their specialities, but also did cased glass, with the amberina laid over milk glass, sometimes with a shiny finish and sometimes with a satin finish. Pictured is a lovely little pitcher in satin-finished cased amberina. This and several other Kanawha Glass pieces are available at Art Glass & Collectibles, http://www.tias.com/stores/agcs.