Purpurin (Italian: ''Porporino''; Latin: ''Haematinum'', derived from Greek ''haimátinos'' = "of blood"; German: ''Hämatinon''), sometimes referred to as ''glass porphyr'', is an opaque glass of brownish to lustrous deep-reddish color which in

classical antiquity Classical antiquity (also the classical era, classical period or classical age) is the period of cultural history between the 8th century BC and the 5th century AD centred on the Mediterranean Sea, comprising the interlocking civilizations of ...

was used for residential luxury objects,

mosaics A mosaic is a pattern or image made of small regular or irregular pieces of colored stone, glass or ceramic, held in place by plaster/mortar, and covering a surface. Mosaics are often used as floor and wall decoration, and were particularly pop ...

and various decorative purposes. Purpurin is somewhat harder than normal glass but can be easily cut and polished. Its red color is permanently lost upon smelting. The material bears some resemblance to goldstone.

Historical references and archeology

Purpurin artifacts are frequently found during archeological excavations of more affluent Roman settlements, often along with actual

Roman glass Roman glass objects have been recovered across the Roman empire, 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 g ...

;

Pompeii Pompeii (, ) was an ancient city located in what is now the ''comune'' of Pompei near Naples in the Campania region of Italy. Pompeii, along with Herculaneum and many villas in the surrounding area (e.g. at Boscoreale, Stabiae), was buried ...

is a prime example.

Pliny the Elder Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...

reports in his '' Historia naturalis'': "Obsidian is made by artificial coloring and used for dishware, and also a completely red and opaque glass called haematinum." The art of making this type of glass seems to have originated in India; glass beads of a similar material have been found in the Indus valley and were dated to the late 2nd millennium BCE.

Rediscovering the technology

The process for "haematinum" (i.e., "blood-red ware") has not been related in any preserved documents from antiquity, and the details of its composition and production remained a mystery until the mid-19th century. Although the German chemist

Martin Heinrich Klaproth Martin Heinrich Klaproth (1 December 1743 – 1 January 1817) was a German chemist. He trained and worked for much of his life as an apothecary, moving in later life to the university. His shop became the second-largest apothecary in Berlin, and ...

had found copper when he analyzed red glass from the

Villa Jovis Villa Jovis ("Villa of Jupiter") is a Roman palace on Capri, southern Italy, built by emperor Tiberius and completed in AD 27. Tiberius ruled mainly from there until his death in AD 37. Villa Jovis is the largest of the twelve Tiberian villas ...

, he mistakenly believed the fabled haematinon was not glass, but rather recast slag from copper smelting. In 1844, Schubarth made a strong case for it being copper-colorated glass, which was later proven to be correct. King

Ludwig I of Bavaria en, Louis Charles Augustus , image = Joseph Karl Stieler - King Ludwig I in his Coronation Robes - WGA21796.jpg , caption = Portrait by Joseph Stieler, 1825 , succession=King of Bavaria , reign = , coronation ...

, who intended to build a reconstruction of a Pompeian villa for educational purposes, assigned

Max Joseph von Pettenkofer Max Joseph Pettenkofer, ennobled in 1883 as Max Joseph von Pettenkofer (3 December 1818 – 10 February 1901) was a Bavarian chemist and hygienist. He is known for his work in practical hygiene, as an apostle of good water, fresh air and proper s ...

to the task of rediscovering the method of manufacturing the antique "blood glass", and indeed the young chemist reported success in 1853.Pettenkofer, M. Ueber einen antiken rothen Glasfluss (Haematinon) und über Aventurin-Glas. Abhandlungen der naturw.-techn. Commission der k. b. Akad. der Wissensch. I. Bd. München, literar.-artist. Anstalt, 1856. His process called for fusing easily smelting standard alkali-lead glass with

copper(II) oxide Copper(II) oxide or cupric oxide is an inorganic compound with the formula CuO. A black solid, it is one of the two stable oxides of copper, the other being Cu2O or copper(I) oxide (cuprous oxide). As a mineral, it is known as tenorite. It i ...

and

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...

in the presence of small amounts of

magnesium oxide Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions ...

and carbon, followed by very slow cooling of the resultant brown mass, which would then take on a deep red color from precipitating microparticles of reduced metallic copper. Subsequently,

Emanuel Kayser Friedrich Heinrich Emanuel Kayser (March 26, 1845November 29, 1927) was a German geologist and palaeontologist, born in Königsberg. He was educated at the universities of Halle, Heidelberg and Berlin, where in 1871 he qualified as a lecturer in ...

realized the brownish tint was attributable to co-precipitated metallic

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

, and that this can be avoided by using

borax Borax is a salt (ionic compound), a hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a basic solution. It is commonly available in powder or granular form, ...

instead of lead glass or lead oxide. His recipe consisted of 60 parts silicon oxide in the form of pure

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

sand, 10 parts calcined borax, 10 parts copper oxide, and 3 parts magnetite.

References

* Meyers Konversations-Lexikon. 4th ed., Leipzig and Vienna 1888; Vol. 8, p. 36 * Brockhaus' Konversations-Lexikon. 14th ed., Leipzig, Berlin and Vienna 1894; Vol. 8, p. 697 * Lueger, O.: Lexikon der gesamten Technik und ihrer Hilfswissenschaften, Stuttgart and Leipzig 1906; Vol. 4, p. 707.

External links

* Replication of the manufacturing technology (April 2002), with illustrations
Roman Glassmakers Newsletter No. 3
Stained glass Ancient Roman glassware History of glass