Opalescent Glass
Above: Three opalescent glass fishes made by Sabino, France in the 1930's. Height: 2.5 inches
Above: Three opalescent glass fishes made by Sabino, France in the 1930's. Height: 2.5 inches
author Angela M. Bowey
There are three kinds of glass which are called "Opalescent". One is the blue-tinged semi-opaque or clear glass with milky opalescence in its centre, typical of Lalique, Sabino, and Jobling's. The three tiny fishes above show this kind of opalescence.
The opalescent colour is produced by the slower cooling of the molten glass in those parts which are thick, causing some crystallization inside the glass.
This kind of opalescent glass glows a golden colour when light shines through from behind it, and a beautiful blue when light shines onto the surface from the front.
You can see this effect if you compare these two pictures of the same vase. The picture on the left shows the subtle golden colour, caused by the light shining through from behind.
The fruit and leaves are raised from the surface (the thickest parts of the vase) and they are more opalescent than the rest of the body (more opaque and opal-colored).
In contrast, the picture on the right shows the same opalescent vase lit from above and in front, and the colouring appears quite different. Opalescent glass of this type appears blue in reflected light.
This vase was commissioned by Etling, a retail shop in Paris during the 1920's and 30's. Etling had a major effect on the style of the time and commissioned a large number of statuettes and vessels in opalescent pressed glass.
Opalescent Lalique glass is amongst the most valued and sought-after pressed glass today. A single plate can cost over a thousand dollars. But in contrast, a piece of opalescent glass by one of the lesser known makers can still be found for a fraction of that price.
There is another kind of opalescent glass where a milky white edge or a white raised pattern decorates a coloured pressed glass item. 
This opalescent effect is produced by re-heating parts of the molten glass when it has just started to cool, and heat-sensitive chemicals in the glass turn the re-heated sections white. The easiest way to do this is to present the newly pressed glass item back to the "glory hole" or furnace entrance, and those parts nearest the heat turn white.
Davidson's of England were one of the major manufacturers of this kind of opalescent glass, giving their version the name "Pearline". 
There were many factories in the USA where this kind of opalescent glass was made during the period 1880 to 1920 (Hobbs, Brockunier; US Glass; Northwood; Fenton; and others). A few (Fenton, for example) were still making similar opalescent glass in this current century.
You can see from the lemon opalescent sugar, cream and butter dish set above (made by Davidson's around 1896), that the amount of white edging varied considerably, depending on how close and for how long the item was reheated. We have an article about Davidson's glass on this site if you would like to know more about that company and its glass. The URL (web address) is http://www.glass.co.nz/Davidson.htm.
Not all opalescent glass was pressed. There were some beautiful pieces made my Louis Comfort Tiffany and Harry Northwood and others which were hand blown into molds that created a raised pattern to which heat was applied.
Tiffany called this kind of glass "Opalescent Optic" or "Opalescent Reactive".
The little vase on the left is the kind which might have been made by Tiffany or Northwood or one of their contemporaries around 1895 to1905.
This third kind of opalescent glass is normally made from two layers of glass. The outer layer contained heat reactive components such as bone ash. The two-layered piece was blown into a mould with the raised pattern impressed into the metal.
After removing the mold, the piece had a raised pattern comprised largely of heat sensitive glass, which turned milky white when reheated.
These hand blown opalescent pieces from the art nouveau period are also highly valued, highly priced, and difficult to find today.
Returning to the French style of opalescent glass, Rene Lalique, like Emile Galle and Louis Comfort Tiffany, was a jeweler and designer before he turned to glass.
His aim as a glass maker was to produce high quality glass using industrial techniques and some mass production.
Even so his pieces were expensive in their day. The 1934 catalogue lists several items over 1000 francs, and one vase (Nadica) cost 3500 francs.
Lalique made table ware, like the plate on the right, vases, statuettes, all kinds of small glass items, and his very famous car mascots. These were made in several colours as well as clear and opalescent.
Rene Lalique's designs were brilliant in their creativity and suitability for bringing out the special features of glass as a medium. The "Lys" bowl, pictured left and below, for example, uses the stems from four flowers to form the legs.
These in turn highlight the opalescence in the glass because they form the thickest section.
All of these designs were converted into metal molds by a Paris mould-maker named Franckhauser, who produced the molds for almost all the major manufacturers of opalescent glass in France in the 1920's and 30's.
This included Marius E. Sabino, the Etling commissions, and the work of Pierre D'Avesn. It has been said that these other French glass makers were imitators of Lalique.
Even if this is true, their work is beautiful in its own right, especially some of their opalescent pieces.
The platter on the left was made by Pierre D'Avesn. It is especially interesting because the background has been deliberately made thick.
The design, in intaglio on the back of the plate, makes the lotus flower heads the thinnest part, and therefore the least opalescent. This platter is almost half an inch thick.
Lalique and the other French glass makers were so successful with high quality pressed glass, that the firm of James A. Jobling, in England, sought a franchise to make and sell French art glass under license in England.
Lalique was not interested, Sabino wanted too much money, and so in 1934 Joblings analysed the constituents of opalescent glass, commissioned Franckhauser to make some molds, ran an in-house competition amongst staff for new designs, and launched their own series of coloured and opalescent quality pressed glass in 1934.
They produced some beautiful pieces and sold them for a fraction of the price of Lalique. The catalogue price (wholesale, admittedly) for the bird design bowl on the right was eighteen shillings per dozen.
Even so, the venture was a failure. They started too late, when the depression was already beginning to bite. And production was ended with the advent of the Second World War in 1939.
Several of the factories which made opalescent glass in the art Deco period are still operating today.
Lalique still make many of the same pieces from the same (presumably renewed) molds. Sabino have moved to the USA but are still producing high quality pressed glass. And Joblings are still operating in the North East of England, now as a division of Corning Glass, and primarily making Pyrex ware.
Left: Miniature cockerel by Sabino, 3 inches high.
From a collectors point of view, there is little danger of mistaking the original art Deco opalescent glass with today's production. Lalique changed the signature on their glass when Rene Lalique died in 1945. If a piece of glass is marked "R. Lalique" then it is from the life-time of Rene, pre-1945 (unless it is a forgery, and there are some of these). 
In addition today's Lalique production is mostly in clear glass, sometimes in coloured glass, and rarely if ever, in opalescent.
There are very few factories making opalescent glass today.
Partly this is because of the level of technical difficulty, and partly because of the poisonous nature of some of the ingredients (typically including traces of arsenic).
Right: small vase by Sabino, approximately 5 inches.
The table below show some typical mixtures for the ingredients of opalescent glass. The ranges relate specifically to the differences between typical French constituents and some of Joblings constituents.
All of the pressed glass described in this article is marked with the manufacturers name and/or a registration number which identifies the manufacturer and the date.
If you are looking for opalescent glass, you can usually find pieces on offer on ebay.
Click Opalescent Glass to see examples. You could also check out our Recommended Books on Glass.
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