Cambridge Blues, Part III

by David B. Rankin
Issue No. 78 - October 1979

This month we will conclude our discussion of the Cambridge blues as we explore the dark blue transparents.

The first group of dark blues is a class known as cobalt blues. This comes from the use of cobalt oxide or other cobalt compounds to achieve the dark blue color. When Cambridge introduced its first cobalt blue, no fancy name was used. It was simply called Cobalt Blue and was referenced in "China, Glass and Lamps" from 1924 to 1926. This time frame is also the peak period for the opaque colors and Rubina, so many of the articles found in Cobalt Blue are also found in these colors.

An example of this color can be seen in Bennett's Color Book, plate 31, row 1, item 4, in a candy jar incorrectly identified as Eleanor Blue. As you can see in this example, Cobalt Blue is a true blue and is much lighter than Royal Blue. Examination of Cobalt Blue under black light provides us with the strongest reaction of all the blues. The fluorescence is an extremely strong, yellow-green.

While examining non-Royal Blue items under black light another dark blue formula was discovered. The reaction of this formula is like night and day compared to the Cobalt formula described above. The reaction is a very weak green fluorescence. Our only clue to the time frame for this color comes from a Decagon plate. As discussed last month Decagon was introduced in 1928. This indicates that this formula is a product of the late 1920's. We found no references to dark blues in this time frame. To provide a basis for reference, I am calling this formula Cobalt Blue II and am now calling the earlier formula Cobalt Blue I. After discovering the Cobalt Blue II color, careful examination of several items in both formulas in natural light reveals that the Cobalt Blue II formula is slightly darker than Cobalt Blue I and has a slight purplish cast. Under artificial lighting this difference is almost impossible to detect. Both colors gather the color effect and look darker in thicker sections of glass.

Welker Color Book II has two items in plate 11, row 2, also incorrectly identified as Eleanor Blue. Although I have not examined these particular items under black light, the decoration on the perfume is generally found on items associated with the late 20's and is probably Cobalt Blue II. Not enough is known about the Buddha to speculate about its color.

In 1931 Cambridge introduced its best known dark blue - Royal Blue. Royal Blue is so dark and dense that it could almost be called an opaque. References to Royal Blue in "China, Glass and Lamps" stopped in 1935 but some pieces of Caprice (introduced in 1936) have been seen. The large number of items listed in the 1940 price list suggests that production of Royal Blue continued beyond 1936 to provide a matching service but that the new lines introduced after 1936 were not made in Royal Blue. For example, have any of you seen any Pristine (1937), Virginian (1938), or Martha (1939) in Royal Blue? It is very easy to describe the reaction of Royal Blue to black light. There is none whatsoever.

Leaving the cobalt blues we move on to another group of dark blues in the blue-green family. We had observed several pieces in this color which dated from the late 1920's. Research in "China, Glass and Lamps" uncovered a few references in 1926 and 1927 to a color called Bluebell. We seemed to have a match but couldn't be sure until one member acquired a pair of bookends like those shown in Bennett's Color Book plate 31, row 3, item 1 (incorrectly identified as Ritz Blue). These bookends had an original Cambridge stock label with the faint but legible word "Bluebell" on it. Other examples of this color can be seen in Welker Color I, plate 12, row 4 (incorrectly identified as Sapphire). Under black light we find a medium, green fluorescence on heavy pressed items and a strong yellow-green reaction on blown ware. To the naked eye the color is just a bit darker than Windex.

We also find another color in the blue-green group that is one of the 8 colors in the Harlequin sets introduced in 1941. It was discontinued in October, 1943, due to war material shortages. A Cambridge advertisement in "Crockery and Glass Journal" in June, 1942, gives us the 8 color names: Tahoe Blue, Moonlight, Forest Green, Gold, Rosa, Mocha, Pistachio and Amethyst. The Statuesque line was one of those made in Harlequin sets.

Upon examination of two 3 ounce Statuesque cocktails from my own collection, I found 2 different colors, neither of which match Bluebell. Thus one of these must be Tahoe Blue, but I have not been able to determine which it is. Under black light one cocktail shows a bright blue-green, medium strength reaction. The other cocktail shows a strong, yellow-green reaction fairly close to, but just a bit stronger than the Bluebell blown formula.

Until this, we had no indication of production in this color range during another period. Until more information is uncovered, I can't even begin to isolate the characteristics of Tahoe Blue.

In summary, the key characteristics of each formula is as follows:

  • 1) Cobalt Blue I (1924-1926) - medium true blue with tendency to appear darker in thick sections. Under black light, extremely strong, yellow-green fluorescence.
  • 2) Cobalt Blue II (late 20's) - darker than Cobalt Blue I, slight purplish cast. Under black light shows weak green reaction.
  • 3) Royal Blue (1931-1935) - dark and dense almost opaque, no reaction to black light.
  • 4) Bluebell (1926-1927) - blue-green color similar to Windex. Under black light:
    a) Pressed formula - medium, green reaction
    b) Blown formula - strong, yellow-green reaction.
  • 5) Unknown blown formula - very similar to Bluebell. Under black light the reaction is the same yellow-green as the blown Bluebell, just a little stronger reaction.
  • 6) Unknown blown formula - similar to Bluebell but a little darker and bluer. Under black light a medium blue-green reaction.
  • 7) Tahoe Blue - characteristics unknown, should be either 5 or 6 above.

Editor's Note: Dave would very much appreciate receiving correspondence from members having comments of any kind concerning the content of this series of articles. Please send letters c/o NCC and they will be forwarded to him.