Until otherwise established, Etling glass items were produced in crystal and opalescent glass. Other coloured glass items are scarce, such as ‘Emerald Green’ and ‘Electric Blue’ and several patterns were only produced using one colour-type.

The recipes used to produce opalescent glass were closely guarded secrets, which involved specific procedures during each stage of the making process. In simplistic terms and for example, various percentages of silicon dioxide, lead oxide, sodium carbonate, potassium oxide, zinc oxide, and arsenic were used. Several other minor additives were required.

However, as with like many glass colour-types, the correct combinations of “cooking-times” & “melting procedures” are what produce the final results. Without precise attention to these details the resulting effects will be futile.

The various combinations of colouring agents used also needed to be compatible with each other, as this can also affect the results. It is worth mentioning that more than 650 different glass colour-types were developed in England alone during the Victorian period.

Opalescent glass effects relied upon both glass making techniques and cooling processes to create the milky pastel-like colours and hues throughout the glass. Once the glass had been annealed and cooled the colouration changed under different conditions of transmitted light. The skillful glassworkers that worked for Etling could, therefore, produce items with specific colour tones upon the edge of a bowl to create wavy-patterns, for example, or within other desirable areas of a design to produce optimum visual appeal. The thickness of the glass also played an important role, as this would also influence the depth and the variety of opalescent colours of a finished piece.

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