Aventurine Glass
Aventurine Glass
According to Professor E. Peligot of France, "Adventurine is a yellowish glass in which there are an infinite number of small crystals of copper, protoxide of copper, or silicate of that oxide. When it is polished, this glass presents, especially in the light, a glittering appearance for which reason it is used in jewelry.
"Many attempts have been made to discover the secret of its manufacture. The skillful chemist, Hautefeuille, has succeeded by perservering efforts in making this glass in considerable quantities: he has just published in the last report of the Societe d'Encouragement [October, 1860] a memoir in which he freely indicates the process he has followed.
"When the glass is very liquid, iron or fine brass turnings enclosed in paper are added, these are incorporated into it by stirring the glass with a red-hot iron rod. The glass becomes blood red, opaque, and at the same time milky and full of bubbles; the draught of the furnace is then stopped, the ash-pan closed, the pot with its lid on is covered with ashes, and it is allowed to cool very slowly. The next day on breaking the pot the Aventurine is seen formed."
In 1865 the chemist Pelouze invented an Aventurine as fine as the finest produced in Venice. The formula he gave was as follows: 250 parts sand, 100 of carbonate of soda, 50 of carbonite of lime, and 40 of bichromate of potash.
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The Venetians, who are credited with the discovery of Aventurine, combined rods of Aventurine with their intricately devised filigree glassware and also sprinkled fine kernels on the body of glass objects. Imitators have never been able to produce Aventurine with that true golden color typical of the Venetian product. The Dalla Venezia family of Venice has been a source of supply to glasshouses all over the world for more than two hundred years.
"The Glass of the Golden Star," as the Chinese poetically call Aventurine, was sold to foreign factories in large clumps or rods by Muranese manufacturers, and these were broken into pieces of suitable size and applied where needed. Particles of green (chrome), pink (chrome in the presence of tin), and bronze Aventurine can be found in nineteenth-century ware of English, Continental and American manufacture. An item in a current newspaper advises us that blue Aventurine is now available in costume jewelry.
The May, 1877, issue of the Crockery and Glass Journal contained a short note to the effect that H. Henkins had patented "gold glassware (granulated gold vases) after the Venetian technique." Unfortunately the writer did not elaborate on this statement, and we do not know where Mr. Henkins was working at this time. Many Continental glass manufacturers exhibited Aventurine glass had come into more or less universal use, and glass factories all over the world were no longer dependent on Venetian sources for their supply.
In 1899 a patent was issue jointly to Edward and Sidney Walsh of Janvier, New Jersey, covering a method for making large articles from pieces of Aventurine. The clods of "Goldstone" were crushed into small bits and spread out in a mold. The mold was placed in a kiln until the pieces melted and fused together. To prevent the copper crystals suspended in the glass from oxidizing, outside air was excluded from the kiln. Irregularies in the surface of the finished article were smoothed down on a wheel.
Fostoria Glass Company of Moundsville, West Virginia, produced green Aventurine glassware. The chrome (green) Aventurine glass was made by supersaturating a high lead glass with chrome oxide. During the melting of the glass batch all the chrome oxide is dissolved in the glass, but as the glass is cooled down to the temperature at which it will be worked or pressed, it is not able to hold in solution all the chrome oxide at the lower temperature. This results in chrome oxide crystals being formed in the glass and these crystals are large enough to reflect light giving the typical appearance of the Aventurine glass.
Articles of glass that appear to have been lightly dusted with gold were manufactured in this way. Powdered gold was either sprinkled on the parison prior to its being fully blown and shaped, or the parison was rolled on a marver that had been covered with powdered gold. When the parison was expanded the gold dust was diffused over the surface of the article, producing the desired effect.
Source: Nineteenth Century Glass - It's Genesis and Development
