Lead glass
Encyclopedia
Lead glass is a variety of glass
in which lead
replaces the calcium
content of a typical potash
glass. Lead glass contains typically 18–40 weight% lead(II) oxide
(PbO), while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO. Lead glass is desirable owing to its decorative properties.
Technically, the term crystal is not applied to glass, as glass, by definition, lacks a crystalline structure
. The use of the term lead crystal remains popular for historical and commercial reasons, and originally stems from the invention in 1674 by Englishman George Ravenscroft 1632-1683, that by adding lead oxide in quantities of between 10 and 30% the appearance of the glass improved and it was easier to melt using sea-coal as a furnace fuel, and had a longer "working period", and the Venetian
use of the word cristallo to describe the rock crystal
imitated by Murano
glassmakers. This naming convention has been maintained to the present day to describe decorative hollow-ware.
and lowers its working temperature and viscosity
. The attractive optical properties of lead glass result from the high content of the heavy metal lead. The high atomic number
of lead also raises the density of the material, since lead has a very high atomic weight
of 207.2, versus 40.08 for calcium. The density of soda glass is 2.4 g/cm3 or below, while typical lead crystal has a density of around 3.1 g/cm3 and high-lead glass can be over 4.0 g/cm3 or even up to 5.9 g/cm3.
The brilliance of lead crystal relies on the high refractive index
caused by the lead content. Ordinary glass has a refractive index of n = 1.5, while the addition of lead produces a range up to 1.7. This heightened refractive index also correlates with increased dispersion
, which measures the degree to which a medium separates light into its component spectra
, as in a prism
. Crystal cutting techniques exploit these properties to create a brilliant, sparkling effect as each cut facet reflects and transmits light through the object. The high refractive index is useful for lens
making, since a given focal length
can be achieved with a thinner lens. However, the dispersion must be corrected by other components of the lens system if it is to be achromatic
.
The addition of lead oxide to potash glass also reduces its viscosity
, rendering it more fluid than ordinary soda glass above softening temperature (about 600 °C), with a working point of 800 °C. The viscosity of glass varies radically with temperature, but that of lead glass is roughly 100 times less than that of ordinary soda glasses across working temperature ranges (up to 1100 °C). From the glassmaker’s perspective, this results in two practical developments. First, lead glass may be worked at a lower temperature, leading to its use in enamelling, and second, clear vessels may be made free from trapped air bubbles with considerably less difficulty than with ordinary glasses, allowing the manufacture of perfectly clear, flawless objects. When tapped, lead crystal makes a ringing sound, unlike ordinary glasses. Consumers still rely on this property to distinguish it from cheaper glasses. Since the potassium ions are bound more tightly in a lead-silica matrix than in a soda-lime glass
, the glass when struck absorbs less energy. This causes the glass to oscillate, thereby producing its characteristic sound. Lead also increases the solubility of tin
, copper
, and antimony
, leading to its use in colored enamels and glaze
s. The low viscosity of lead glass melt is the reason for typically high lead oxide content in the glass solders.
The presence of lead is used in glasses absorbing gamma radiation and X-ray
s, used in radiation shielding (e.g. in cathode ray tube
s, where lowering the exposure of the viewer to soft X-rays is of concern).
The high ionic radius
of the Pb2+ ion renders it highly immobile in the matrix and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda-lime glass (108.5 vs 106.5 Ohm·cm, DC
at 250 °C). Lead-containing glass is therefore frequently used in light fixture
s.
. The lead oxide used in lead glass could be obtained from a variety of sources. In Europe, galena
, lead sulfide, was widely available, which could be smelted
to produce metallic lead. The lead metal would be calcined
to form lead oxide by roasting it and scraping off the litharge
. In the medieval period
lead metal could be obtained through recycling from abandoned Roman sites and plumbing, even from church roofs. Metallic lead was demanded in quantity for silver cupellation
, and the resulting litharge could be used directly by glassmakers. Lead was also used for ceramic lead glazes. This material interdependence suggests a close working relationship between potters, glassmakers, and metalworkers.
Glasses with lead oxide content first appeared in Mesopotamia
, the birthplace of the glass industry. The earliest known example is a blue glass fragment from Nippur
dated to 1400 BC containing 3.66% PbO, and is mentioned in clay tablets from the reign of Assurbanipal (668–631 BC), and a recipe for lead glaze appears in a Babylonian tablet of 1700 BC. A red sealing-wax cake found in the Burnt Palace at Nimrud
, from the early 6th century BC, contains 10% PbO. These low values suggest that lead oxide may not have been consciously added, and was certainly not used as the primary fluxing agent in ancient glasses.
Lead glass also occurs in Han
-period China (206 BC – 220 AD). Here it was used in cast to imitate jade, both for ritual objects such as big and small figures, as well as jewellery and a limited range of vessels. Since glass occurs at such a late date in China, it is thought that the technology was brought along the Silk Road
by glassworkers from the Middle East. The fundamental compositional difference between Western silica-natron
glass and the unique Chinese lead glass, however, may indicate a quite different development.
In medieval and early modern Europe
lead glass was used as a base in coloured glasses, specifically in mosaic tessera
e, enamels, stained-glass
painting, and bijouterie, where it was used to imitate precious stones
. Several textual sources describing lead glass survive. In his Schedula Diversarum Artium (List Sundry Crafts' ), Theophilus
describes its use as imitation gemstone, and the title of a lost chapter mentions the use of lead in glass. The 12–13th century Heraclius
details the manufacture of lead enamel and its use for window painting in his De Coloribus et artibus Romanorum (Of for Huereds and Crafts Romans' ). This refers to lead glass as “Jewish glass”, perhaps indicating its transmission to Europe. A manuscript preserved at San Marco
, Venice, describes the use of lead oxide in enamels and includes recipes for calcining lead to form the oxide. Lead glass was ideally suited for enamelling vessels and windows owing to its lower working temperature than the forest glass body.
Antonio Neri
devoted his entire book four of his L’Arte Vetraria to lead glass, first published in 1612. In this first systematic treatise on glass, he again refers to the use of lead glass in enamels, glassware, and for the imitation of precious stones. Christopher Merrett
translated this into English in 1662 (The Art of Glass), paving the way for the production of English lead crystal glass by George Ravenscroft.
George Ravenscroft
(1618–1681) was the first to produce clear lead crystal glassware on an industrial scale. The son of a merchant with close ties to Venice, Ravenscroft had the cultural and financial resources necessary to revolutionise the glass trade, allowing England to overtake Venice as the centre of the glass industry in the eighteenth and nineteenth centuries. With the aid of Venetian glassmakers, especially da Costa, and under the auspices of the Glass Sellers Guild, Ravenscroft sought to find an alternative to Venetian cristallo. His use of flint as the silica source has led to the term flint glass
to describe these crystal glasses, despite his later switch to sand. At first, his glasses tended to crizzle, developing a network of small cracks destroying its transparency, which was eventually overcome by replacing some of the potash flux with lead oxide to the melt, up to 30%. Crizzling results from the destruction of the glass network by an excess of alkali, and may be caused by excess humidity as well as inherent defects in glass composition. He was granted a protective patent in 1673, where production and refinement moved from his glasshouse on the Savoy to the seclusion of Henley-on-Thames
, and in 1676, having apparently overcome the crizzling problem, was granted the use of a raven’s head seal as a guaranty of quality. In 1681, the year of his death, the patent expired and operations quickly developed amongst several firms, where by 1696 twenty-seven of the eighty-eight glasshouses in England were producing flint glass containing 30–35% PbO, especially at London and Bristol.
At this period, glass was sold by weight, and the typical forms were rather heavy and solid with minimal decoration. Such was its success on the international market, however, that in 1746 the British Government imposed a lucrative tax by weight. Rather than drastically reduce the lead content of their glass, manufacturers responded by creating highly-decorated, smaller, more-delicate forms, often with hollow stems, known to collectors today as Excise glasses. In 1780, the Government granted Ireland free trade in glass without taxation. English labour and capital then shifted to Dublin and Belfast, and new glassworks specialising in cut glass were installed in Cork and Waterford
. In 1825, the tax was renewed, and gradually the industry declined until the mid-nineteenth century, when they were finally repealed.
From this period, English lead glass became popular throughout Europe, and was ideally suited to the new taste for wheel-cut glass decoration perfected on the Continent owing to its relatively soft properties. In Holland, local engraving masters such as David Wolff and Frans Greenwood stippled imported English glassware, a style that remained popular through the eighteenth century. Such was its popularity in Holland that the first Continental production of lead-crystal glass began there, probably as the result of imported English workers. Imitating lead-crystal à la façon d’Angleterre presented technical difficulties, as the best results were obtained with covered pots in a coal-fired furnace, a particularly English process requiring specialised cone-furnaces. Towards the end of the eighteenth century, lead-crystal glass was being produced in France, Germany, and Norway. By 1800, Anglo-Irish
lead crystal had overtaken lime-potash glasses on the Continent, and traditional glassmaking centres in Bohemia began to focus on colored glasses rather than compete directly against it.
The development of lead glass continued through the twentieth century, when in 1932 scientists at the Corning Glassworks, New York, developed a new lead glass of high optical clarity. This became the focus of Steuben glassworks, a division of Corning, which produced decorative vases, bowls, and glasses in Art Deco
style. Lead-crystal continues to be used in industrial and decorative applications.
. Lead glazes first appear in first century BC to first century AD Roman wares, and occur nearly simultaneously in China. They were very high in lead, 45–60% PbO, with a very low alkali content, less than 2%. From the Roman period, they remained popular through the Byzantine and Islamic periods in the Near East
, on pottery vessels and tiles throughout medieval Europe, and up to the present day. In China, similar glazes were used from the twelfth century for colored enamels on stoneware, and on porcelain from the fourteenth century.
These could be applied in three different ways. Lead could be added directly to a ceramic body in the form of a lead compound in suspension, either from galena
(PbS), red lead
(Pb3O4), white lead
(2PbCO3·Pb(OH)2), or lead oxide
(PbO). The second method involves mixing the lead compound with silica, which is then placed in suspension and applied directly. The third method involves fritting the lead compound with silica, powdering the mixture, and suspending and applying it. The method used on a particular vessel may be deduced by analysing the interaction layer between the glaze and the ceramic body microscopically.
Tin-opacified glazes appear in Iraq in the eighth century AD. Originally containing 1–2% PbO, by the eleventh century high-lead glaze had developed, typically containing 20–40% PbO and 5–12% alkali. These were used throughout Europe and the Near East, especially in Iznik ware
, and continue to be used today. Glazes with even-higher lead content occur in Spanish and Italian maiolica, with up to 55% PbO and as low as 3% alkali. Adding lead to the melt allows the formation of tin oxide
more readily than in an alkali glaze, which precipitates into crystals in the glaze as it cools, creating its opacity.
The use of lead glaze has several advantages over alkali glazes in addition to their greater optical refractivity. Lead compounds in suspension may be added directly to the ceramic body. Alkali glazes must first be mixed with silica and fritted prior to use, since they are soluble in water, requiring additional work input. A successful glaze must not crawl, or peel away from the pottery surface upon cooling, leaving areas of unglazed ceramic. Lead reduces this risk by reducing the surface tension
of the glaze. It must not craze, forming a network of cracks, nor peel. This is caused when the thermal contraction
of the glaze and the ceramic body do not match properly. Ideally, the glaze contraction should be 5–15% less than the body contraction, as glazes are stronger under compression than under tension. A high-lead glaze has a linear expansion coefficient of between 5 and 7×10−6/°C, compared to 9 to 10×10−6/°C for alkali glazes. Those of earthenware ceramics vary between 3 and 5×10−6/°C for non-calcareous bodies and 5 to 7×10−6/°C for calcareous clays, or those containing 15–25% CaO. Therefore the thermal contraction of lead glaze matches that of the ceramic more closely than an alkali glaze, rendering it less prone to crazing. A glaze should also have a low enough viscosity to prevent the formation of pinholes as trapped gasses escape during firing, typically between 900–1100 °C, but not so low as to run off. The relatively-low viscosity of lead glaze mitigates this issue. It may also have been cheaper to produce than alkali glazes.
Lead glass and glazes have a long and complex history, and continue to play new roles in industry and technology today.
Lead oxide
added to the molten glass gives lead crystal a much higher index of refraction than normal glass, and consequently much greater "sparkle" by increasing specular reflection
and the range of angles of total internal reflection
. Ordinary glass has a refractive index of n = 1.5; the addition of lead produces an index of refraction of up to 1.7. This heightened refractive index also raises the correlating index of dispersion
, which measures the degree to which a medium separates light into its component spectra, as in a prism
. This increase in refractive index from 1.5 to 1.7 significantly increases the amount of light reflected (by a factor of 1.68 for light reflecting in the normal direction; see Fresnel equations
).
In cut glass, which has been hand- or machine-cut with facets, the presence of lead also makes the glass softer and easier to cut. Crystal can consist of up to 35% lead, at which point it has the most sparkle.
Makers of lead crystal objects include
with the upper classes in Europe and America was, in part, caused by their extensive use of lead crystal decanters to store fortified wine
s and whisky
. Lin et al. have statistical evidence linking gout to lead poisoning
.
Items made of lead glass may leach lead into the food and beverages contained. In a study performed at North Carolina State University
, the amount of lead migration was measured for Port wine
stored in lead crystal decanter
s.
After two days, lead levels were 89 µg/L (micrograms per liter). After four months, lead levels were between 2,000 and 5,000 µg/L.
White wine doubled its lead content within an hour of storage and tripled it within four hours. Some brandy stored in lead crystal for over five years had lead levels around 20,000 µg/L. To put this into perspective, the U.S. Environmental Protection Agency's lead standard for drinking water is 15 µg/L = 15 parts per billion.
Citrus juices and other acidic drinks leach lead from crystal as effectively as alcoholic beverages. When lead-glass beverage containers are used in the ordinary usual way they do not pose a health risk. Under conditions of repeated use of the decanter, the lead leaching steeply decreases with increasing use. This finding is "consistent with ceramic chemistry theory, which predicts that leaching of Pb from crystal is self-limiting exponentially as a function of increasing distance from the crystal-liquid interface." Lead leaching still occurs, but the quantity that leaches into a glass of wine or other beverage let stand for a few hours is much smaller than the quantity of lead consumed daily in ordinary diet. An ordinary diet contains about 70 µg of lead per day.
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...
in which lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
replaces the calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
content of a typical potash
Potash
Potash is the common name for various mined and manufactured salts that contain potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains, and this was the major historical source for it before the industrial era...
glass. Lead glass contains typically 18–40 weight% lead(II) oxide
Lead(II) oxide
Lead oxide is the inorganic compound with the formula PbO. Lead oxide occurs in two polymorphs, red, having a tetragonal crystal structure and yellow, having an orthorhombic crystal structure...
(PbO), while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO. Lead glass is desirable owing to its decorative properties.
Technically, the term crystal is not applied to glass, as glass, by definition, lacks a crystalline structure
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
. The use of the term lead crystal remains popular for historical and commercial reasons, and originally stems from the invention in 1674 by Englishman George Ravenscroft 1632-1683, that by adding lead oxide in quantities of between 10 and 30% the appearance of the glass improved and it was easier to melt using sea-coal as a furnace fuel, and had a longer "working period", and the Venetian
Venetian language
Venetian or Venetan is a Romance language spoken as a native language by over two million people, mostly in the Veneto region of Italy, where of five million inhabitants almost all can understand it. It is sometimes spoken and often well understood outside Veneto, in Trentino, Friuli, Venezia...
use of the word cristallo to describe the rock crystal
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
imitated by Murano
Murano
Murano is a series of islands linked by bridges in the Venetian Lagoon, northern Italy. It lies about 1.5 km north of Venice and measures about across with a population of just over 5,000 . It is famous for its glass making, particularly lampworking...
glassmakers. This naming convention has been maintained to the present day to describe decorative hollow-ware.
Properties
The addition of lead oxide to glass raises its refractive indexRefractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
and lowers its working temperature and viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
. The attractive optical properties of lead glass result from the high content of the heavy metal lead. The high atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
of lead also raises the density of the material, since lead has a very high atomic weight
Atomic mass
The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....
of 207.2, versus 40.08 for calcium. The density of soda glass is 2.4 g/cm3 or below, while typical lead crystal has a density of around 3.1 g/cm3 and high-lead glass can be over 4.0 g/cm3 or even up to 5.9 g/cm3.
The brilliance of lead crystal relies on the high refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
caused by the lead content. Ordinary glass has a refractive index of n = 1.5, while the addition of lead produces a range up to 1.7. This heightened refractive index also correlates with increased dispersion
Dispersion (optics)
In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency, or alternatively when the group velocity depends on the frequency.Media having such a property are termed dispersive media...
, which measures the degree to which a medium separates light into its component spectra
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
, as in a prism
Prism (optics)
In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use...
. Crystal cutting techniques exploit these properties to create a brilliant, sparkling effect as each cut facet reflects and transmits light through the object. The high refractive index is useful for lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
making, since a given focal length
Focal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
can be achieved with a thinner lens. However, the dispersion must be corrected by other components of the lens system if it is to be achromatic
Achromatic lens
An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths into focus in the same plane....
.
The addition of lead oxide to potash glass also reduces its viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
, rendering it more fluid than ordinary soda glass above softening temperature (about 600 °C), with a working point of 800 °C. The viscosity of glass varies radically with temperature, but that of lead glass is roughly 100 times less than that of ordinary soda glasses across working temperature ranges (up to 1100 °C). From the glassmaker’s perspective, this results in two practical developments. First, lead glass may be worked at a lower temperature, leading to its use in enamelling, and second, clear vessels may be made free from trapped air bubbles with considerably less difficulty than with ordinary glasses, allowing the manufacture of perfectly clear, flawless objects. When tapped, lead crystal makes a ringing sound, unlike ordinary glasses. Consumers still rely on this property to distinguish it from cheaper glasses. Since the potassium ions are bound more tightly in a lead-silica matrix than in a soda-lime glass
Soda-lime glass
Soda-lime glass, also called soda-lime-silica glass, is the most prevalent type of glass, used for windowpanes, and glass containers for beverages, food, and some commodity items...
, the glass when struck absorbs less energy. This causes the glass to oscillate, thereby producing its characteristic sound. Lead also increases the solubility of 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...
, copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
, and antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
, leading to its use in colored enamels and glaze
Ceramic glaze
Glaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.-Use:...
s. The low viscosity of lead glass melt is the reason for typically high lead oxide content in the glass solders.
The presence of lead is used in glasses absorbing gamma radiation and X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s, used in radiation shielding (e.g. in cathode ray tube
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
s, where lowering the exposure of the viewer to soft X-rays is of concern).
The high ionic radius
Ionic radius
Ionic radius, rion, is the radius of an atom's ion. Although neither atoms nor ions have sharp boundaries, it is important to treat them as if they are hard spheres with radii such that the sum of ionic radii of the cation and anion gives the distance between the ions in a crystal lattice...
of the Pb2+ ion renders it highly immobile in the matrix and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda-lime glass (108.5 vs 106.5 Ohm·cm, DC
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
at 250 °C). Lead-containing glass is therefore frequently used in light fixture
Light fixture
A light fixture, light fitting, or luminaire is an electrical device used to create artificial light and/or illumination, by use of an electric lamp...
s.
| use | PbO (wt.%) |
|---|---|
| Household "crystal" leaded glass | 18–38 |
| Ceramic glaze Ceramic glaze Glaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.-Use:... s and vitreous enamel Vitreous enamel Vitreous enamel, also porcelain enamel in U.S. English, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C... s |
16–35 |
| High refractive index Refractive index In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium.... optical glasses |
4–65 |
| Radiation shielding | 2–28 |
| High electrical resistance Electrical resistance The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical... |
20–22 |
| Glass solders and sealants | 56–77 |
History
Lead may be introduced into glass either as an ingredient of the primary melt or added to preformed leadless glass or fritFrit
Frit is a ceramic composition that has been fused in a special fusing oven, quenched to form a glass, and granulated. Frits form an important part of the batches used in compounding enamels and ceramic glazes; the purpose of this pre-fusion is to render any soluble and/or toxic components insoluble...
. The lead oxide used in lead glass could be obtained from a variety of sources. In Europe, galena
Galena
Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...
, lead sulfide, was widely available, which could be smelted
Smelting
Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores...
to produce metallic lead. The lead metal would be calcined
Calcination
Calcination is a thermal treatment process applied to ores and other solid materials to bring about a thermal decomposition, phase transition, or removal of a volatile fraction. The calcination process normally takes place at temperatures below the melting point of the product materials...
to form lead oxide by roasting it and scraping off the litharge
Litharge
Litharge is one of the natural mineral forms of lead oxide, PbO. Litharge is a secondary mineral which forms from the oxidation of galena ores. It forms as coatings and encrustations with internal tetragonal crystal structure. It is dimorphous with the orthorhombic form massicot...
. In the medieval period
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...
lead metal could be obtained through recycling from abandoned Roman sites and plumbing, even from church roofs. Metallic lead was demanded in quantity for silver cupellation
Cupellation
Cupellation is a metallurgical process in which ores or alloyed metals are treated under high temperatures and carefully controlled operations in order to separate noble metals, like gold and silver, from base metals like lead, copper, zinc, arsenic, antimony or bismuth, that might be present in...
, and the resulting litharge could be used directly by glassmakers. Lead was also used for ceramic lead glazes. This material interdependence suggests a close working relationship between potters, glassmakers, and metalworkers.
Glasses with lead oxide content first appeared in Mesopotamia
Mesopotamia
Mesopotamia is a toponym for the area of the Tigris–Euphrates river system, largely corresponding to modern-day Iraq, northeastern Syria, southeastern Turkey and southwestern Iran.Widely considered to be the cradle of civilization, Bronze Age Mesopotamia included Sumer and the...
, the birthplace of the glass industry. The earliest known example is a blue glass fragment from Nippur
Nippur
Nippur was one of the most ancient of all the Sumerian cities. It was the special seat of the worship of the Sumerian god Enlil, the "Lord Wind," ruler of the cosmos subject to An alone...
dated to 1400 BC containing 3.66% PbO, and is mentioned in clay tablets from the reign of Assurbanipal (668–631 BC), and a recipe for lead glaze appears in a Babylonian tablet of 1700 BC. A red sealing-wax cake found in the Burnt Palace at Nimrud
Nimrud
Nimrud is an ancient Assyrian city located south of Nineveh on the river Tigris in modern Ninawa Governorate Iraq. In ancient times the city was called Kalḫu. The Arabs called the city Nimrud after the Biblical Nimrod, a legendary hunting hero .The city covered an area of around . Ruins of the city...
, from the early 6th century BC, contains 10% PbO. These low values suggest that lead oxide may not have been consciously added, and was certainly not used as the primary fluxing agent in ancient glasses.
Lead glass also occurs in Han
Han Dynasty
The Han Dynasty was the second imperial dynasty of China, preceded by the Qin Dynasty and succeeded by the Three Kingdoms . It was founded by the rebel leader Liu Bang, known posthumously as Emperor Gaozu of Han. It was briefly interrupted by the Xin Dynasty of the former regent Wang Mang...
-period China (206 BC – 220 AD). Here it was used in cast to imitate jade, both for ritual objects such as big and small figures, as well as jewellery and a limited range of vessels. Since glass occurs at such a late date in China, it is thought that the technology was brought along the Silk Road
Silk Road
The Silk Road or Silk Route refers to a historical network of interlinking trade routes across the Afro-Eurasian landmass that connected East, South, and Western Asia with the Mediterranean and European world, as well as parts of North and East Africa...
by glassworkers from the Middle East. The fundamental compositional difference between Western silica-natron
Natron
Natron is a naturally occurring mixture of sodium carbonate decahydrate and about 17% sodium bicarbonate along with small quantities of household salt and sodium sulfate. Natron is white to colourless when pure, varying to gray or yellow with impurities...
glass and the unique Chinese lead glass, however, may indicate a quite different development.
In medieval and early modern Europe
Early modern Europe
Early modern Europe is the term used by historians to refer to a period in the history of Europe which spanned the centuries between the end of the Middle Ages and the beginning of the Industrial Revolution, roughly the late 15th century to the late 18th century...
lead glass was used as a base in coloured glasses, specifically in mosaic tessera
Tessera
A tessera is an individual tile in a mosaic, usually formed in the shape of a cube. It is also known as an abaciscus, abaculus, or, in Persian کاشي معرق. In antiquity, mosaics were formed from naturally colored pebbles, but by 200 BC purpose-made tesserae were being used...
e, enamels, stained-glass
Stained glass
The term stained glass can refer to coloured glass as a material or to works produced from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant buildings...
painting, and bijouterie, where it was used to imitate precious stones
Gemstone
A gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...
. Several textual sources describing lead glass survive. In his Schedula Diversarum Artium (List Sundry Crafts
Theophilus Presbyter
Theophilus Presbyter is the pseudonymous author or compiler ofa Latin text containing detailed descriptions of various medieval arts, a text commonly known as the Schedula diversarum artium or De diversis artibus , probably first compiled between 1100 and 1120...
describes its use as imitation gemstone, and the title of a lost chapter mentions the use of lead in glass. The 12–13th century Heraclius
Heraclius
Heraclius was Byzantine Emperor from 610 to 641.He was responsible for introducing Greek as the empire's official language. His rise to power began in 608, when he and his father, Heraclius the Elder, the exarch of Africa, successfully led a revolt against the unpopular usurper Phocas.Heraclius'...
details the manufacture of lead enamel and its use for window painting in his De Coloribus et artibus Romanorum (Of for Huereds and Crafts Romans
San Marco
San Marco is one of the six sestieri of Venice, lying in the heart of the city. San Marco also includes the island of San Giorgio Maggiore...
, Venice, describes the use of lead oxide in enamels and includes recipes for calcining lead to form the oxide. Lead glass was ideally suited for enamelling vessels and windows owing to its lower working temperature than the forest glass body.
Antonio Neri
Antonio Neri
Antonio Neri was a Florentine priest who published L’Arte Vetraria or The Art of Glass in 1612. His father was a physician, and he was an herbalist, alchemist, and glassmaker. Neri traveled extensively in Italy and Holland.-References:...
devoted his entire book four of his L’Arte Vetraria to lead glass, first published in 1612. In this first systematic treatise on glass, he again refers to the use of lead glass in enamels, glassware, and for the imitation of precious stones. Christopher Merrett
Christopher Merrett
Christopher Merret FRS was an English physician and scientist. He was the first to document the deliberate addition of sugar for the production of sparkling wine, and produced the first list of British birds.-Life:Merret was born in Winchcombe, Gloucestershire on 16 February; Hunter gives the...
translated this into English in 1662 (The Art of Glass), paving the way for the production of English lead crystal glass by George Ravenscroft.
George Ravenscroft
George Ravenscroft
George Ravenscroft was an English businessman in the import/export and glass making trades. He is primarily known for his work in developing clear lead crystal glass in England.-Personal life:...
(1618–1681) was the first to produce clear lead crystal glassware on an industrial scale. The son of a merchant with close ties to Venice, Ravenscroft had the cultural and financial resources necessary to revolutionise the glass trade, allowing England to overtake Venice as the centre of the glass industry in the eighteenth and nineteenth centuries. With the aid of Venetian glassmakers, especially da Costa, and under the auspices of the Glass Sellers Guild, Ravenscroft sought to find an alternative to Venetian cristallo. His use of flint as the silica source has led to the term flint glass
Flint glass
Flint glass is optical glass that has relatively high refractive index and low Abbe number. Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less. The currently known flint glasses have refractive indices ranging between 1.45 and 2.00...
to describe these crystal glasses, despite his later switch to sand. At first, his glasses tended to crizzle, developing a network of small cracks destroying its transparency, which was eventually overcome by replacing some of the potash flux with lead oxide to the melt, up to 30%. Crizzling results from the destruction of the glass network by an excess of alkali, and may be caused by excess humidity as well as inherent defects in glass composition. He was granted a protective patent in 1673, where production and refinement moved from his glasshouse on the Savoy to the seclusion of Henley-on-Thames
Henley-on-Thames
Henley-on-Thames is a town and civil parish on the River Thames in South Oxfordshire, England, about 10 miles downstream and north-east from Reading, 10 miles upstream and west from Maidenhead...
, and in 1676, having apparently overcome the crizzling problem, was granted the use of a raven’s head seal as a guaranty of quality. In 1681, the year of his death, the patent expired and operations quickly developed amongst several firms, where by 1696 twenty-seven of the eighty-eight glasshouses in England were producing flint glass containing 30–35% PbO, especially at London and Bristol.
At this period, glass was sold by weight, and the typical forms were rather heavy and solid with minimal decoration. Such was its success on the international market, however, that in 1746 the British Government imposed a lucrative tax by weight. Rather than drastically reduce the lead content of their glass, manufacturers responded by creating highly-decorated, smaller, more-delicate forms, often with hollow stems, known to collectors today as Excise glasses. In 1780, the Government granted Ireland free trade in glass without taxation. English labour and capital then shifted to Dublin and Belfast, and new glassworks specialising in cut glass were installed in Cork and Waterford
Waterford
Waterford is a city in the South-East Region of Ireland. It is the oldest city in the country and fifth largest by population. Waterford City Council is the local government authority for the city and its immediate hinterland...
. In 1825, the tax was renewed, and gradually the industry declined until the mid-nineteenth century, when they were finally repealed.
From this period, English lead glass became popular throughout Europe, and was ideally suited to the new taste for wheel-cut glass decoration perfected on the Continent owing to its relatively soft properties. In Holland, local engraving masters such as David Wolff and Frans Greenwood stippled imported English glassware, a style that remained popular through the eighteenth century. Such was its popularity in Holland that the first Continental production of lead-crystal glass began there, probably as the result of imported English workers. Imitating lead-crystal à la façon d’Angleterre presented technical difficulties, as the best results were obtained with covered pots in a coal-fired furnace, a particularly English process requiring specialised cone-furnaces. Towards the end of the eighteenth century, lead-crystal glass was being produced in France, Germany, and Norway. By 1800, Anglo-Irish
Anglo-Irish
Anglo-Irish was a term used primarily in the 19th and early 20th centuries to identify a privileged social class in Ireland, whose members were the descendants and successors of the Protestant Ascendancy, mostly belonging to the Church of Ireland, which was the established church of Ireland until...
lead crystal had overtaken lime-potash glasses on the Continent, and traditional glassmaking centres in Bohemia began to focus on colored glasses rather than compete directly against it.
The development of lead glass continued through the twentieth century, when in 1932 scientists at the Corning Glassworks, New York, developed a new lead glass of high optical clarity. This became the focus of Steuben glassworks, a division of Corning, which produced decorative vases, bowls, and glasses in Art Deco
Art Deco
Art deco , or deco, is an eclectic artistic and design style that began in Paris in the 1920s and flourished internationally throughout the 1930s, into the World War II era. The style influenced all areas of design, including architecture and interior design, industrial design, fashion and...
style. Lead-crystal continues to be used in industrial and decorative applications.
Lead glazes
The fluxing and refractive properties valued for lead glass also make it attractive as a pottery or ceramic glazeCeramic glaze
Glaze is a layer or coating of a vitreous substance which has been fired to fuse to a ceramic object to color, decorate, strengthen or waterproof it.-Use:...
. Lead glazes first appear in first century BC to first century AD Roman wares, and occur nearly simultaneously in China. They were very high in lead, 45–60% PbO, with a very low alkali content, less than 2%. From the Roman period, they remained popular through the Byzantine and Islamic periods in the Near East
Near East
The Near East is a geographical term that covers different countries for geographers, archeologists, and historians, on the one hand, and for political scientists, economists, and journalists, on the other...
, on pottery vessels and tiles throughout medieval Europe, and up to the present day. In China, similar glazes were used from the twelfth century for colored enamels on stoneware, and on porcelain from the fourteenth century.
These could be applied in three different ways. Lead could be added directly to a ceramic body in the form of a lead compound in suspension, either from galena
Galena
Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...
(PbS), red lead
Red lead
Lead tetroxide, also called minium, red lead or triplumbic tetroxide, is a bright red or orange crystalline or amorphous pigment. Chemically, red lead is lead tetroxide, Pb3O4, or 2PbO·PbO2....
(Pb3O4), white lead
White lead
White lead is the chemical compound 2·Pb2. It was formerly used as an ingredient for lead paint and a cosmetic called Venetian Ceruse, because its opaque quality made it a good pigment. However, it tended to cause lead poisoning, and its use has been banned in most countries.White lead has been...
(2PbCO3·Pb(OH)2), or lead oxide
Lead(II) oxide
Lead oxide is the inorganic compound with the formula PbO. Lead oxide occurs in two polymorphs, red, having a tetragonal crystal structure and yellow, having an orthorhombic crystal structure...
(PbO). The second method involves mixing the lead compound with silica, which is then placed in suspension and applied directly. The third method involves fritting the lead compound with silica, powdering the mixture, and suspending and applying it. The method used on a particular vessel may be deduced by analysing the interaction layer between the glaze and the ceramic body microscopically.
Tin-opacified glazes appear in Iraq in the eighth century AD. Originally containing 1–2% PbO, by the eleventh century high-lead glaze had developed, typically containing 20–40% PbO and 5–12% alkali. These were used throughout Europe and the Near East, especially in Iznik ware
Iznik pottery
İznik pottery, named after the town in western Anatolia where it was made, is highly decorated ceramics that was produced between the late 15th and 17th centuries....
, and continue to be used today. Glazes with even-higher lead content occur in Spanish and Italian maiolica, with up to 55% PbO and as low as 3% alkali. Adding lead to the melt allows the formation of tin oxide
Tin(II) oxide
Tin oxide is a compound of tin and oxygen where tin has the oxidation state of +2. There are two forms, a stable blue-black form and a metastable red form.-Preparation and reactions:...
more readily than in an alkali glaze, which precipitates into crystals in the glaze as it cools, creating its opacity.
The use of lead glaze has several advantages over alkali glazes in addition to their greater optical refractivity. Lead compounds in suspension may be added directly to the ceramic body. Alkali glazes must first be mixed with silica and fritted prior to use, since they are soluble in water, requiring additional work input. A successful glaze must not crawl, or peel away from the pottery surface upon cooling, leaving areas of unglazed ceramic. Lead reduces this risk by reducing the surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
of the glaze. It must not craze, forming a network of cracks, nor peel. This is caused when the thermal contraction
Thermal expansion
Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are rare; this effect is...
of the glaze and the ceramic body do not match properly. Ideally, the glaze contraction should be 5–15% less than the body contraction, as glazes are stronger under compression than under tension. A high-lead glaze has a linear expansion coefficient of between 5 and 7×10−6/°C, compared to 9 to 10×10−6/°C for alkali glazes. Those of earthenware ceramics vary between 3 and 5×10−6/°C for non-calcareous bodies and 5 to 7×10−6/°C for calcareous clays, or those containing 15–25% CaO. Therefore the thermal contraction of lead glaze matches that of the ceramic more closely than an alkali glaze, rendering it less prone to crazing. A glaze should also have a low enough viscosity to prevent the formation of pinholes as trapped gasses escape during firing, typically between 900–1100 °C, but not so low as to run off. The relatively-low viscosity of lead glaze mitigates this issue. It may also have been cheaper to produce than alkali glazes.
Lead glass and glazes have a long and complex history, and continue to play new roles in industry and technology today.
Lead crystal
Lead(II) oxide
Lead oxide is the inorganic compound with the formula PbO. Lead oxide occurs in two polymorphs, red, having a tetragonal crystal structure and yellow, having an orthorhombic crystal structure...
added to the molten glass gives lead crystal a much higher index of refraction than normal glass, and consequently much greater "sparkle" by increasing specular reflection
Specular reflection
Specular reflection is the mirror-like reflection of light from a surface, in which light from a single incoming direction is reflected into a single outgoing direction...
and the range of angles of total internal reflection
Total internal reflection
Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is...
. Ordinary glass has a refractive index of n = 1.5; the addition of lead produces an index of refraction of up to 1.7. This heightened refractive index also raises the correlating index of dispersion
Dispersion (optics)
In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency, or alternatively when the group velocity depends on the frequency.Media having such a property are termed dispersive media...
, which measures the degree to which a medium separates light into its component spectra, as in a prism
Prism (optics)
In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use...
. This increase in refractive index from 1.5 to 1.7 significantly increases the amount of light reflected (by a factor of 1.68 for light reflecting in the normal direction; see Fresnel equations
Fresnel equations
The Fresnel equations , deduced by Augustin-Jean Fresnel , describe the behaviour of light when moving between media of differing refractive indices...
).
In cut glass, which has been hand- or machine-cut with facets, the presence of lead also makes the glass softer and easier to cut. Crystal can consist of up to 35% lead, at which point it has the most sparkle.
Makers of lead crystal objects include
| Name | Polity |
|---|---|
| Baccarat Baccarat (company) Baccarat Crystal is a manufacturer of fine crystal glassware located in Baccarat, France. The company owns two museums: the Musée Baccarat in Baccarat, Meurthe-et-Moselle and the Galerie-Musée Baccarat, on the Place des États-Unis in Paris... |
France France The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France... |
| Arc International | France France The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France... |
| Royal Leerdam Crystal Royal Leerdam Crystal Royal Leerdam Crystal, also known as Royal Leerdam, is the designing and glass blowing department of Dutch glassware producing factory, Glasfabriek Leerdam. The company was founded in 1765 as a manufacturer of bottles in the Dutch city of Leerdam.... |
Netherlands Netherlands The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders... |
| Steuben Glass | United States United States The United States of America is a federal constitutional republic comprising fifty states and a federal district... |
| Waterford Crystal Waterford Crystal Waterford Crystal is a trademark brand of crystal glassware, previously produced in Waterford, Ireland, though the factory there was shut down after the receivership of Waterford Wedgwood plc in early 2009... |
Ireland Ireland Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth... |
| Mikasa | Japan Japan Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south... |
| NovaScotian Crystal | Canada Canada Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean... |
| Liuligongfang | Taiwan Taiwan Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following... |
| Swarovski Swarovski Swarovski is the brand name for a range of precisely-cut crystal and related luxury products produced by Swarovski AG of Wattens, Austria... |
Austria Austria Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the... |
| Preciosa Preciosa (corporation) Preciosa is the luxury brand name for the range of precision-cut lead crystal glass and related products produced by Preciosa a.s. of Jablonec nad Nisou, Czech Republic.-History of Preciosa Company:... |
Czech Republic Czech Republic The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest.... |
Safety
It has been proposed that the historic association of goutGout
Gout is a medical condition usually characterized by recurrent attacks of acute inflammatory arthritis—a red, tender, hot, swollen joint. The metatarsal-phalangeal joint at the base of the big toe is the most commonly affected . However, it may also present as tophi, kidney stones, or urate...
with the upper classes in Europe and America was, in part, caused by their extensive use of lead crystal decanters to store fortified wine
Fortified wine
Fortified wine is wine to which a distilled beverage has been added. Fortified wine is distinguished from spirits made from wine in that spirits are produced by means of distillation, while fortified wine is simply wine that has had a spirit added to it...
s and whisky
Whisky
Whisky or whiskey is a type of distilled alcoholic beverage made from fermented grain mash. Different grains are used for different varieties, including barley, malted barley, rye, malted rye, wheat, and corn...
. Lin et al. have statistical evidence linking gout to lead poisoning
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...
.
Items made of lead glass may leach lead into the food and beverages contained. In a study performed at North Carolina State University
North Carolina State University
North Carolina State University at Raleigh is a public, coeducational, extensive research university located in Raleigh, North Carolina, United States. Commonly known as NC State, the university is part of the University of North Carolina system and is a land, sea, and space grant institution...
, the amount of lead migration was measured for Port wine
Port wine
Port wine is a Portuguese fortified wine produced exclusively in the Douro Valley in the northern provinces of Portugal. It is typically a sweet, red wine, often served as a dessert wine, and comes in dry, semi-dry, and white varieties...
stored in lead crystal 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.
After two days, lead levels were 89 µg/L (micrograms per liter). After four months, lead levels were between 2,000 and 5,000 µg/L.
White wine doubled its lead content within an hour of storage and tripled it within four hours. Some brandy stored in lead crystal for over five years had lead levels around 20,000 µg/L. To put this into perspective, the U.S. Environmental Protection Agency's lead standard for drinking water is 15 µg/L = 15 parts per billion.
Citrus juices and other acidic drinks leach lead from crystal as effectively as alcoholic beverages. When lead-glass beverage containers are used in the ordinary usual way they do not pose a health risk. Under conditions of repeated use of the decanter, the lead leaching steeply decreases with increasing use. This finding is "consistent with ceramic chemistry theory, which predicts that leaching of Pb from crystal is self-limiting exponentially as a function of increasing distance from the crystal-liquid interface." Lead leaching still occurs, but the quantity that leaches into a glass of wine or other beverage let stand for a few hours is much smaller than the quantity of lead consumed daily in ordinary diet. An ordinary diet contains about 70 µg of lead per day.
See also
- Steuben Crystal
- Waterford CrystalWaterford CrystalWaterford Crystal is a trademark brand of crystal glassware, previously produced in Waterford, Ireland, though the factory there was shut down after the receivership of Waterford Wedgwood plc in early 2009...
- Edinburgh CrystalEdinburgh CrystalEdinburgh Crystal was a cut glass crystal manufactured in Scotland between 1867 and 2006, and was also the name of the manufacturing company. In addition to drinking glasses, Edinburgh Crystal have made decanters, bowls, baskets, and bells, in several ranges...
- SwarovskiSwarovskiSwarovski is the brand name for a range of precisely-cut crystal and related luxury products produced by Swarovski AG of Wattens, Austria...
- NovaScotian Crystal
- List of indices of refraction
- LeadLeadLead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
- Hot cellHot cellShielded nuclear radiation containment chambers are commonly referred to as hot cells. The word "hot" refers to radioactivity.Hot cells are used in both the nuclear-energy and the nuclear-medicines industries....
- Val Saint LambertVal Saint LambertVal Saint Lambert is a Belgian crystal glassware manufacturer, founded in 1826. Val St Lambert is the official glassware supplier to H.M. King Albert II of Belgium.-History:...