Cranberry glass
Encyclopedia
Gold(III) chloride
Gold chloride, traditionally called auric chloride, is a chemical compound of gold and chlorine. With the molecular formula Au2Cl6, the name gold trichloride is a simplification, referring to the empirical formula. The Roman numerals in the name indicate that the gold has an oxidation state of +3,...
to molten glass. Tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
, in the form of stannous chloride, is sometimes added in tiny amounts as a reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...
. The glass is used primarily in expensive decorations.
Cranberry glass is made in craft production
Craft production
Craft production is the process of manufacturing by hand with or without the aid of tools. The term Craft production refers to a manufacturing technique applied in the hobbies of Handicraft but was also the common method of manufacture in the pre-industrialized world...
rather than in large quantities, due to the high cost of the gold and the delicate mixing process required. The gold chloride is made by dissolving gold in a solution of nitric acid and hydrochloric acid (aqua regia
Aqua regia
Aqua regia or aqua regis is a highly corrosive mixture of acids, fuming yellow or red solution, also called nitro-hydrochloric acid. The mixture is formed by freshly mixing concentrated nitric acid and hydrochloric acid, usually in a volume ratio of 1:3, respectively...
). The glass is typically hand blown or molded. The finished, hardened glass is a type of colloid
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...
, a solid phase (gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
) dispersed inside another solid phase (glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
).
The origins of cranberry glass making are murky. Some historians believe a form of this glass was first made in the late Roman Empire
Roman Empire
The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....
. The craft was then lost and rediscovered in the 17th century by either Johann Kunckel
Johann von Löwenstern-Kunckel
Johann Kunckel, awarded Swedish nobility in 1693 under the name von Löwenstern-Kunckel , German chemist, was born in 1630 , near Rendsburg, his father being alchemist to the court of Holstein...
in Potsdam
Potsdam
Potsdam is the capital city of the German federal state of Brandenburg and part of the Berlin/Brandenburg Metropolitan Region. It is situated on the River Havel, southwest of Berlin city centre....
or by the Florentine
Florence
Florence is the capital city of the Italian region of Tuscany and of the province of Florence. It is the most populous city in Tuscany, with approximately 370,000 inhabitants, expanding to over 1.5 million in the metropolitan area....
glassmaker Antonio Neri in Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
. But neither of them knew the mechanism which yielded the colour. Chemist and winner of the 1925 Nobel Prize in Chemistry
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
Richard Adolf Zsigmondy
Richard Adolf Zsigmondy
Richard Adolf Zsigmondy was an Austrian-Hungarian chemist and Nobel laureate for chemistry known for his research in colloids. The crater Zsigmondy on the Moon is named in his honour....
was able to understand and explain that small colloid
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...
s of gold were responsible for the red colour.
The most famous period of cranberry glass production was in 19th century Britain
United Kingdom of Great Britain and Ireland
The United Kingdom of Great Britain and Ireland was the formal name of the United Kingdom during the period when what is now the Republic of Ireland formed a part of it....
during the Victorian Era
Victorian era
The Victorian era of British history was the period of Queen Victoria's reign from 20 June 1837 until her death on 22 January 1901. It was a long period of peace, prosperity, refined sensibilities and national self-confidence...
.
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 confectioneries or flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s. Cranberry glass was also frequently used for wine glasses, decanter
Decanter
A decanter is a vessel that is used to hold the decantation of a liquid which may contain sediment. Decanters are normally used as serving vessels for wine. Decanters vary in shape and design. They are usually made of an inert material and will hold at least one standard bottle of wine...
s, and finger bowl
Finger bowl
A finger bowl is a bowl of water, usually with lemon or flower petals, which is used for rinsing one's fingers in between courses in a multiple course meal. It is typically served before the dessert course, on a doily on top of the dessert plate....
s. Cranberry glass was also well-known for its use in "Mary Gregory
Mary Gregory
Mary Gregory was an American glass painter at the Boston and Sandwich Glass Company in Cape Cod, Massachusetts who helped popularize glass-painting.-Victorian children:...
" glass. This glass had a white enamel fired onto the glass in a design, usually of romantic variety.