Sculptured/Swirled Cups: Comparing Suprema & Corning Ware  

Both are patterned with Callaway.  The cup on the left is made of Corning Ware, on the right is Suprema.

Cups in the Sculptured, swirled Enhancements style and the similarly tapered Occasions style were made of Suprema from about 1988 to 1998.  Following that, they were made of Corning Ware from 1999 to 2002 approximately.  Comparing cups made of these two different glass-ceramics emphasizes that although Suprema cups are marked with the Corning brand name, they are clearly not made of Corning Ware. 

The main objectives in the development of Suprema were to create a glass-ceramic that is highly break-resistant, microwave-safe, and matches Vitrelle as closely as possible in appearance.  Stove-top use was not a consideration at all.  So this formula and the method of manufacture are substantially different than that of Corning Ware. 

A large part of Suprema's strength is in its glaze of clear glass which forms a compression layer over the base material.  This behaves very much like Vitrelle's three layered glass laminate structure.  It is also a concept similar to Centura, another glazed glass-ceramic with incredible strength, but one which fails on the microwave use aspect.  Conversely, Corning Ware is not glazed at all; it is self-glazing, meaning that its base material is capable of producing a smooth surface spontaneously during heat-treatment.

This Corning Ware cup is branded 'Corningware' and the Suprema cup is branded 'Corning'.  The lettering on the Corning Ware cup is smooth and well-defined, while Suprema's lettering is a bit rough and low on the surface.  Some Corning Ware cups do bear the 'Corning' brand, so in reality more can be learned from feeling the backstamp than from reading it.  Additionally Suprema's glazing process leaves tell-tale marks on the bottom which are not found on real Corning Ware.  On each piece of Suprema there are three rough unglazed spots, and this is evidence of the rack supporting the piece during heat treatment.  These spots can also be found on Centura.

Suprema has a soft white colour with a slight translucency and a high-gloss sheen.  Corelle also possesses these qualities and Suprema makes an excellent match.  Corning Ware is very solidly opaque without the glassy shine, but it is adequately smooth.  Cups made of Corning Ware are sometimes thicker, and more often heavier than those of Suprema, but there is a fair amount of variance with this aspect.

Many Suprema cups are decorated under the glaze and this can result in the colours appearing lighter than usual, but this also means the pattern is protected within the glass and will never fade.  The decorations on Corning Ware cups sit on the surface and they can be prone to fading under very harsh conditions.  This is more true of multi-coloured designs than of one-colour patterns, and it depends on the decorating technique too.

(Photo:  Opaque Corning Ware cup at top, translucent Suprema at bottom.)

Related Articles:

What is Suprema?
Suprema Flared Mugs 
Compare Straight-Sided Suprema & Stoneware Mugs 
Pattern List: Sculptured Cups