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Cranberry glass or Gold Ruby glass is a red glass made by adding
The origins of cranberry glass making are unknown, but many historians believe a form of this glass was first made in the late
gold salts
Gold-containing drugs are pharmaceuticals that contain gold. Sometimes these species are referred to as "gold salts". "Chrysotherapy" and "aurotherapy" are the applications of gold compounds to medicine. Research on the medicinal effects of g ...
or colloidal gold
Colloidal gold is a sol or colloidal suspension of nanoparticles of gold in a fluid, usually water. The colloid is usually either wine-red coloured (for spherical particles less than 100 nm) or blue/purple (for larger spherical particl ...
to molten glass. Tin, in the form of stannous chloride, is sometimes added in tiny amounts as a reducing agent
In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ).
Examples of substances that are commonly reducing agents include the Earth met ...
. The glass is used primarily in expensive decorations.
Production
Cranberry glass is made incraft production
Craft production is manufacturing by hand, with or without the aid of tools. The term "craft production" describes manufacturing techniques that are used in handicraft trades. They were the common methods of manufacture in the pre-industrialize ...
rather than in large quantities, due to the high cost of the gold. The gold chloride is made by dissolving gold in a solution of nitric acid and hydrochloric acid ( aqua regia). The glass is typically hand blown or molded. The finished, hardened glass is a type of colloid
A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...
, a solid phase (gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
) dispersed inside another solid phase (glass
Glass is a non- crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenchin ...
).
History
The origins of cranberry glass making are unknown, but many historians believe a form of this glass was first made in the late Roman Empire
The Roman Empire ( la, Imperium Romanum ; grc-gre, Βασιλεία τῶν Ῥωμαίων, Basileía tôn Rhōmaíōn) was the post-Roman Republic, Republican period of ancient Rome. As a polity, it included large territorial holdings aro ...
. This is evidenced by the British Museum
The British Museum is a public museum dedicated to human history, art and culture located in the Bloomsbury area of London. Its permanent collection of eight million works is among the largest and most comprehensive in existence. It docum ...
's collection Lycurgus Cup, a 4th-century Roman glass
Roman glass objects have been recovered across the Roman Empire in domestic, industrial and funerary contexts. Glass was used primarily for the production of vessels, although mosaic tiles and window glass were also produced. Roman glass productio ...
cage cup
A cage cup, also ''vas diatretum'', plural ''diatreta'', or "reticulated cup" is a type of luxury late Roman glass vessel, found from roughly the 4th century, and "the pinnacle of Roman achievements in glass-making". ''Diatreta'' consist of a ...
made of a dichroic glass, which shows a different colour depending on whether light is passing through it or reflecting from it; red (gold salts) when lit from behind and green (silver salts) when lit from in front.
The craft was then lost and rediscovered in the 17th century Bohemia
Bohemia ( ; cs, Čechy ; ; hsb, Čěska; szl, Czechy) is the westernmost and largest historical region of the Czech Republic. Bohemia can also refer to a wider area consisting of the historical Lands of the Bohemian Crown ruled by the Bohem ...
n period by either Johann Kunckel in Potsdam
Potsdam () is the capital and, with around 183,000 inhabitants, largest city of the German state of Brandenburg. It is part of the Berlin/Brandenburg Metropolitan Region. Potsdam sits on the River Havel, a tributary of the Elbe, downstream of ...
or by the Florentine glassmaker Antonio Neri. Neither of them knew the mechanism which yielded the colour, however. Chemist and winner of the 1925 Nobel Prize in Chemistry
)
, image = Nobel Prize.png
, alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "M ...
Richard Adolf Zsigmondy was able to understand and explain that small colloid
A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend ...
s of gold were responsible for the red colour.
The most famous period of cranberry glass production was in 19th century Britain during the Victorian Era
In the history of the United Kingdom and the British Empire, the Victorian era was the period of Queen Victoria's reign, from 20 June 1837 until her death on 22 January 1901. The era followed the Georgian period and preceded the Edwa ...
.
Legend holds that cranberry glass was first discovered when a noble tossed a gold coin into a mixture of molten glass. This legend is almost certainly not true, as the gold must be dissolved in aqua regia before being added to the molten glass.
Cranberry glass creations were most popular as a table display, often holding candy
Candy, also called sweets (British English) or lollies (Australian English, New Zealand English), is a confection that features sugar as a principal ingredient. The category, called ''sugar confectionery'', encompasses any sweet confection, i ...
or flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanis ...
s.
Cranberry glass was also frequently used for wine glasses, decanters, and finger bowls. Cranberry glass was also well known for its use in "Mary Gregory
Mary Gregory (1856–1908) was an American artist known for her decoration of glass products at the Boston and Sandwich Glass Company in Cape Cod, Massachusetts. Gregory worked for Boston and Sandwich from 1880 to 1884. Gregory painted lamps ...
" glass. This glass had a white enamel fired onto the glass in a design, usually with a romantic theme.
See also
*Purple of Cassius
Purple of Cassius is a purple pigment formed by the reaction of gold salts with tin(II) chloride. It has been used to impart glass with a red coloration (see ''cranberry glass''), as well as to determine the presence of gold as a chemical test.
...
* '' Heart of Glass'', a 1976 film by Werner Herzog
Werner Herzog (; born 5 September 1942) is a German film director, screenwriter, author, actor, and opera director, regarded as a pioneer of New German Cinema. His films often feature ambitious protagonists with impossible dreams, people with u ...
on the secret of ruby glass
References
External links
* * * {{DEFAULTSORT:Cranberry Glass Glass art Glass trademarks and brands Glass compositions Craft materials