View source for Lead glass

{{Short description|Variety of glass in which lead replaces the calcium content}}
{{see also|leaded glass (disambiguation)}}
{{Use dmy dates|date=August 2022}}

[[File:Crystal_glass.jpg|thumb|right|300x300px|[[Cut glass]] wine glass made of lead glass]]

'''Lead glass''', commonly called '''crystal''', is a variety of [[glass]] in which [[lead]] replaces the [[calcium]] content of a typical [[potash]] glass.<ref name="newton">{{cite book|last= Newton|first= Roy G.
|author2=Sandra Davison |title= Conservation of Glass|year = 1989
|series = Butterworth – Heinemann Series in Conservation and Museology| publisher = [[Butterworth-Heinemann|Butterworths]]
| location = London|isbn= 0-408-10623-9}}</ref> Lead glass typically contains 18–40% (by mass) [[lead(II) oxide]] (PbO); modern '''lead crystal''' or '''leaded crystal''',<ref>{{cite web |last=Schwarcz |first=Joe |date=8 March 2019 |title=Alcohol should not be stored in leaded crystal decanters |url=https://www.mcgill.ca/oss/article/it-dangerous-store-alcoholic-beverages-decanters-made-lead-crystal |website=McGill Office for Science and Society |publisher=McGill University |access-date=}}</ref> historically also known as [[flint glass]] for the original [[silica]] source, contains a minimum of 24% PbO.<ref name="hurst-vose" /> Lead glass is desirable for a variety of uses due to its clarity.<ref name=benv>{{Cite book|url=https://books.google.com/books?id=O_5eCAAAQBAJ&pg=PA93|title=Industrial Chemistry: For Advanced Students|last=Benvenuto|first=Mark Anthony|date=2015-02-24|publisher=Walter de Gruyter GmbH & Co KG|isbn=9783110351705|language=en}}</ref>  In marketing terms it is often called '''crystal glass'''.

The term ''lead crystal'' is, technically, not an accurate way to describe lead glass, because glass lacks a [[crystal structure|crystalline structure]] and is instead an [[amorphous solid]]. The use of the term remains popular for historical and commercial reasons but is sometimes changed to simply ''crystal'' because of lead's reputation as a toxic substance. It is retained from the [[Venetian language|Venetian]] word {{lang|vec|cristallo}} to describe the rock crystal ([[quartz]]) imitated by [[Murano]] glassmakers. This naming convention has been maintained to the present day to describe decorative [[holloware]].<ref name=tait/>

Lead crystal [[glassware]] was formerly used to store and serve drinks, but the [[lead poisoning|health risks of lead]] have made this use rare. An alternative material is modern crystal glass, in which [[barium oxide]], [[zinc oxide]], or [[potassium oxide]] are employed instead of lead oxide.

In the [[European Union]], labelling of "crystal" products is regulated by [[Directive (European Union)|Council Directive]] 69/493/EEC, which defines four categories, depending on the chemical composition and properties of the material. Only glass products containing at least 24% lead oxide may be referred to as "lead crystal". Products with less lead oxide, and glass products with other metal oxides used in place of lead oxide, must be labelled "crystalline" or "crystal glass".<ref>{{cite web|url=http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31969L0493:en:NOT|title=Council Directive 69/493/EEC of 15 December 1969 on the approximation of the laws of the Member States relating to crystal glass|date=15 December 1969 }}</ref>

==Properties==
The addition of lead oxide to glass raises its [[refractive index]] and lowers its working temperature and [[viscosity]]. The attractive optical properties of lead glass result from the high content of the [[Heavy metal (chemistry)|heavy metal]] lead. Lead, whose density is more than seven times that of calcium, also raises the density of the glass. The density of soda glass is {{convert|abbr=on|2.4|g/cm3|oz/cuin|lk=in}} or below, while typical lead crystal has a density of around {{cvt|3.1|g/cm3|oz/in3||}} and high-lead glass can be over {{cvt|4.0|g/cm3|oz/in3||}} or even up to {{cvt|5.9|g/cm3|oz/in3||}}.<ref name=newton/>

The brilliance of lead crystal arises from the high [[refractive index]] caused by the lead content. Ordinary glass has a refractive (''n'') of 1.5, while the addition of lead produces a range up to 1.7<ref name=newton/> or 1.8.<ref>[http://physics.info/refraction/ Refraction of media tutorial]. physics.info</ref> This increased refractive index also correlates with increased [[dispersion (optics)|dispersion]], a measure of the degree to which a medium separates light into its component wavelengths, thus producing a spectrum of colors just as a [[prism (optics)|prism]] does. Crystal cutting techniques exploit these properties to create a brilliant, sparkling effect as each cut facet in [[cut glass]] reflects and transmits light through the object. The high refractive index is useful for [[lens (optics)|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 the lens is to be [[achromatic lens|achromatic]].

The addition of lead oxide to potash glass also reduces its [[viscosity]], rendering it more fluid than ordinary soda glass above its softening temperature (about {{convert|abbr=on|600|°C|F|disp=or}}), with a working point of {{convert|abbr=on|800|°C|F}}. The viscosity of glass varies radically with temperature, but that of lead glass is roughly two orders of magnitude lower than that of ordinary soda glasses across working temperature ranges (up to {{convert|abbr=on|1100|°C|F| disp=or}}).<ref>NIST via https://glassproperties.com/viscosity/</ref> From the glassmaker's perspective, this results in two practical effects. First, lead glass may be worked at a lower temperature, facilitating its use in [[enamelling]]; second, clear vessels may be made without trapped air bubbles with 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. Wine glasses made of lead glass are valued for the "ring" made by the [[clinking glasses|clinking of glasses]]. The sound was considered better when a large quantity of lead oxide was present in the glassmaking material, as in the British and Irish wine glasses of the 17th-19th centuries, with their "rich bell-notes of [[F (musical note)|F]] and [[G♯ (musical note)|G sharp]]".{{sfn|Visser|2015|p=220}} Consumers still rely on this property to distinguish lead glass from cheaper glasses. Emil Deeg had published a major study{{sfn|Kurkjian|Kieffer|2001|p=348}} on the ringing of the lead crystal in 1958.{{sfn|Deeg|1958}}
Since the potassium ions are bound more tightly in a lead-silica matrix than in a [[soda–lime glass]], the former absorbs more energy when struck{{dubious|date=January 2020}}. This causes the lead crystal to [[oscillate]], thereby producing its characteristic sound.<ref name=newton/> Lead also increases the solubility of [[tin]], [[copper]], and [[antimony]], leading to its use in colored enamels and [[ceramic glaze|glaze]]s. The low viscosity of lead glass melt is the reason for typically high lead oxide content in the [[glass solder]]s.

[[File:Fluoroscopy room with control space.jpg|thumb|Fluoroscopy room with control space separated by [[lead shielding]] glass]]
The presence of lead is used in glasses absorbing [[gamma radiation]] and [[X-ray]]s, used in [[radiation shielding]] as a form of [[lead shielding]] (e.g. in [[cathode-ray tube]]s, thus lowering the exposure of the viewer to soft X-rays).  In [[particle physics]], the combination of the low [[radiation length]] resulting from the high density and presence of heavy nuclei with the high refractive index which leads to both pronounced [[Cherenkov radiation]] and containment of the Cherenkov light by [[total internal reflection]] makes lead glass one of the prominent tools for [[Calorimeter (particle physics)|photon detection]] by means of [[Particle shower#Electromagnetic showers|electromagnetic showers]].

The high [[ionic radius]] of the Pb<sup>2+</sup> 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 (10<sup>8.5</sup> vs 10<sup>6.5</sup> ohm·cm, [[direct current|DC]] at {{convert|abbr=on|250|°C|F|disp=or}}).<ref>{{cite book|url=https://books.google.com/books?id=ASIYuNCp81YC&q=%22glass+solders%22&pg=PA158 |title=Ceramic and Glass Materials: Structure, Properties and Processing|page=158|author=James F. Shackelford, Robert H. Doremus|publisher=Springer|year=2008|isbn=978-0-387-73361-6}}</ref> Lead-containing glass is frequently used in [[light fixture]]s.

{| class="wikitable"
|-
! Use
! PbO by weight (%)
|-
| Household "crystal" leaded glass || 18–38
|-
| [[Ceramic glaze]]s and [[vitreous enamel]]s || 16–35
|-
| High [[refractive index]] optical glasses || 4–65
|-
| [[Radiation shielding]] || 2–28
|-
| High [[electrical resistance]] || 20–22
|-
| [[Glass solder]]s and sealants || 56–77
|}

==History==
Lead may be introduced into glass either as an ingredient of the primary melt or as an addition to preformed leadless glass or [[frit]]. The lead oxide used in lead glass can be obtained from a variety of sources. In Europe, [[galena]]{{nbsp}}– lead sulfide{{nbsp}}– was widely available, and it could be [[Smelting|smelted]] to produce metallic lead. The lead metal was [[Calcination|calcined]] to form lead oxide by roasting it and scraping off the [[litharge]]. In the [[Middle Ages|medieval period]] lead metal could be obtained through recycling from abandoned Roman sites and plumbing, including 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.<ref name=fiori>{{cite book
|last = Fiori|first = Cesare|author2=Mariangela Vandini
 | title = When Glass Matters: Studies in the History of Science and Art from Graeco-Roman Antiquity to Early Modern Era| chapter = Chemical Composition of Glass and its Raw Materials| editor = Marco Beretta| year = 2004| publisher = Olschki
| location = Florence |isbn= 88-222-5318-3
}}</ref>

Glasses with lead oxide content first appeared in [[Mesopotamia]], the [[History of glass|birthplace of the glass industry]].<ref name="tait">{{cite book|title=Five Thousand Years of Glass|publisher=[[University of Pennsylvania Press]] (orig. [[British Museum|British Museum Press]])|year=2004|isbn=978-0-8122-1888-6|editor=Tait, Hugh}}</ref> The earliest known example is a blue glass fragment from [[Nippur]] dated to 1400 BC containing 3.66% PbO. Glass 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.<ref name=charleston>{{cite journal |doi=10.1111/j.1475-4754.1960.tb00508.x |title=Lead in Glass |year=1960 |last1=Charleston |first1=R. J. |journal=Archaeometry |volume=3 |issue=1 |pages=1–4|bibcode=1960Archa...3....1C }}</ref> 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 dynasty|Han-period China]] (206 BC{{nbsp}}–  220 AD). There, it was 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 first occurs at such a late date in China, it is thought that the technology was brought along [[Silk Road|the Silk Road]] by glassworkers from the Middle East.<ref name=tait/> The fundamental compositional difference between Western silica-[[natron]] glass and the unique Chinese lead glass, however, may indicate an autonomous 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|stained-glass]] painting, and ''bijouterie'', where it was used to imitate [[gemstone|precious stones]]. Several textual sources describing lead glass survive. In the late 11th–early 12th century, ''Schedula Diversarum Artium'' (''List of Sundry Crafts''), the author known as "[[Theophilus Presbyter]]" describes its use as imitation gemstone, and the title of a lost chapter of the work mentions the use of lead in glass. The 12–13th century pseudonymous "Heraclius" details the manufacture of lead enamel and its use for window painting in his ''De coloribus et artibus Romanorum'' (''Of Hues and Crafts of the Romans''). This refers to lead glass as "Jewish glass", perhaps indicating its transmission to Europe.<ref name=charleston/> A manuscript preserved in the [[Biblioteca Marciana]], 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]] of the body.

[[Antonio Neri]] devoted book four of his ''L'Arte Vetraria'' ("The Art of Glass-making", 1612) to lead glass. 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, setting the basis from which England overtook Venice and Bohemia 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 Worshipful Company of Glass Sellers of London, 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.<ref name="hurst-vose">{{cite book|last=Hurst-Vose|first=Ruth|title=Glass|publisher=[[HarperCollins|Collins]]|year=1980|isbn=0-00-211379-1|series=Collins Archaeology|location=London}}</ref> At first, his glasses tended to [[wikt:crizzle|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.<ref name=newton/> He was granted a protective patent in 1673, where production moved from his glasshouse in the [[precinct of the Savoy]], London, to the seclusion of [[Henley-on-Thames]].<ref name=macleod>{{cite journal |doi=10.2307/3105182 |jstor=3105182 |pages=776–803 |last1=MacLeod |first1=Christine |title=Accident or Design? George Ravenscroft's Patent and the Invention of Lead-Crystal Glass |volume=28 |issue=4 |journal=Technology and Culture |year=1987}}</ref> In 1676, having apparently overcome the crizzling problem, Ravenscroft 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 among several firms, where by 1696 twenty-seven of the eighty-eight glasshouses in England, especially at London and Bristol, were producing flint glass containing 30–35% PbO.<ref name=hurst-vose/>

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''.<ref name=hurst-vose/> 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 [[Art glass#Cut glass|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 the tax was finally repealed.<ref name=tait/>

From the 18th century, 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.<ref name=tait/> 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.<ref name=charleston/> 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.<ref name=hurst-vose/> Towards the end of the eighteenth century, lead-crystal glass was being produced in France, Hungary, Germany, and Norway.<ref name=charleston/><ref name="Ajka Kristály">{{cite web |url=http://ajka-crystal.hu/en/aboutus |title=About us – Ajka Kristály |location=Ajka, Hungary |publisher=Ajka Kristály |access-date=16 August 2012 |archive-url=https://web.archive.org/web/20121220080518/http://ajka-crystal.hu/en/aboutus |archive-date=20 December 2012 |url-status=dead }}</ref> By 1800, [[Ireland|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 Inc.|Corning Glassworks]], New York State, developed a new lead glass of high optical clarity. This became the focus of [[Steuben Glass Works]], 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==
The fluxing and refractive properties valued for lead glass also make it attractive as a pottery or [[ceramic glaze]]. 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%.<ref name=tite>{{cite journal |doi=10.1111/j.1475-4754.1998.tb00836.x |title=Lead Glazes in Antiquity—methods of Production and Reasons for Use |year=1998 |last1=Tite |first1=M. S. |last2=Freestone |first2=I. |last3=Mason |first3=R. |last4=Molera |first4=J. |last5=Vendrell-Saz |first5=M. |last6=Wood |first6=N. |journal=Archaeometry |volume=40 |issue=2 |pages=241–60|bibcode=1998Archa..40..241T }}</ref> 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]] (Pb<sub>3</sub>O<sub>4</sub>), [[white lead]] (2PbCO<sub>3</sub>·Pb(OH)<sub>2</sub>), or [[Lead(II) oxide|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.<ref name=tite/> The method used on a particular vessel may be deduced by analysing the interaction layer between the glaze and the ceramic body microscopically.

[[Tin glazing|Tin-opacified glazes]] appear in Iraq in the eighth century AD. Originally containing 1–2% PbO; by the eleventh century high-lead glazes had developed, typically containing 20–40% PbO and 5–12% alkali. These were used throughout Europe and the Near East, especially in [[Iznik pottery|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.<ref name=tite/> Adding lead to the melt allows the formation of [[tin(II) oxide|tin oxide]] more readily than in an alkali glaze: tin oxide 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 [[frit]]ted prior to use, since they are soluble in water, requiring additional labor. 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, caused when the [[thermal expansion|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<sup>−6</sup>/°C, compared to 9 to 10×10<sup>−6</sup>/°C for alkali glazes. Those of earthenware ceramics vary between 3 and 5×10<sup>−6</sup>/°C for non-calcareous bodies and 5 to 7×10<sup>−6</sup>/°C for calcareous clays, or those containing 15–25% CaO.<ref name=tite/> 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 and 1100&nbsp;°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.<ref name=tite/>
Lead glass and glazes have a long and complex history, and continue to play new roles in industry and technology today.

==Lead crystal==
[[File:Crystbeads.jpg|thumb|Lead crystal beads]]
[[Lead(II) oxide|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.<ref name="newton"/> This higher refractive index also raises the correlated [[dispersion (optics)|dispersion]], the degree to which the glass separates light into its colors, as in a [[prism (optics)|prism]]. The increases in refractive index and dispersion significantly increase the amount of reflected light and thus the "fire" in the glass.

In [[Art glass#Cut glass|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.<ref name="newton"/>

Makers of lead crystal objects include:

{| class="wikitable sortable"
|-
!Name
!Polity
!Production began
!Notes
|-
|[[NovaScotian Crystal]]
|[[Canada]]
|1996
|Production discontinued March 2021
|-
|[[Gus Crystal]]
|[[Russia]]
|1756
|Production continued
|-
|[[Baccarat (company)|Baccarat]]
|[[France]]
|1816
|Part of the [[Starwood Capital Group]] since 2005
|-
|[[Saint-Louis (glass manufacturer)|Saint-Louis]]
|[[France]]
|1781
|Part of [[Hermès]] since 1989
|-
|[[Lalique]]
|[[France]]
|1920s
|Part of the [[Art & Fragrance]] since 2011
|-
|[[Daum (studio)|Daum]]
|[[France]]
|1878
|Part of [[Financiere Saint-Germain]] since 2009 after bankruptcy in 2003
|-
|[[Luminarc|Arc International]]
|[[France]]
|1968
|Production of [[Arc International#Cristal d'Arques|Crystal D'Arque]] ended in 2009; restarted in 2010 as lead-free Diamax.
|-
|[[Dartington Crystal]]
|[[England]]
|1967
|Management buy out in 2006.
|-
|[[Cumbria Crystal]]
|[[England]]
|1976
|Last remaining Luxury Cut Crystal producer in the UK.
|-
|[[Royal Brierley]]
|[[England]]
|1776
|Trademark of the [[Dartington Crystal]] since 2006
|-
|[[Waterford Crystal]]
|[[Republic of Ireland]]
|1783
|[[Waterford Wedgwood|WWRD Holdings]] of [[KPS Capital Partners]] after bankruptcy in 2009.
|-
|[[Galway Crystal]]
|[[Republic of Ireland]]
|
|
|-
|[[Tipperary Crystal]]
|[[Republic of Ireland]]
|1987
|Founded by former [[Waterford Crystal]] craftsmen.
|-
|[[Cavan Crystal]]
|[[Republic of Ireland]]
|
|
|-
|[[Tyrone Crystal]]
|[[Northern Ireland]]
|1971
|Factory closed 2010
|-
|[[Dingle Crystal]]
|[[Republic of Ireland]]
|1998
|
|-
|[[Edinburgh Crystal]]
|[[Scotland]]
|1867
|Trademark of the WWRD Holdings after bankruptcy in 2006
|-
|[[Hadeland Glassverk]]
|[[Norway]]
|1765
|Production continued
|-
|[[Kristal Samobor]]
|[[Croatia]]
|1839
|Production continued
|-
|[[Magnor Glassverk]]
|[[Norway]]
|1830
|Production continued
|-
|[[Orrefors glassworks]]
|[[Sweden]]
|1913
|Part of the Swedish glassworks group [[Orrefors Kosta Boda AB]] since 2005
|-
|[[Kosta Boda]]
|[[Sweden]]
|1742
|Part of the Swedish glassworks group [[Orrefors Kosta Boda AB]] since 2005
|-
|[[Holmegaard Glass Factory]]
|[[Denmark]]
|1825
|Production ceased in 2009
|-
|[[Val Saint Lambert]]
|[[Belgium]]
|1826
|Sold to [[Onclin]] winemaker family for $5M in 2008
|-
|[[Mozart Crystal]]
|[[Brazil]]
|2018
|Production continued
|-
|[[Royal Leerdam Crystal]]
|[[Netherlands]]
|1765
|Merged with porcelain factory [[De Koninklijke Porceleyne Fles]] in 2008
|-
|[[Zwiesel Kristallglas]]
|[[Germany]]
|1872
|Management buy out at [[Schott AG]] in 2001. Only crystal manufacturer in Germany
|-
|[[Nachtmann (glass manufacturer)|Nachtmann]]
|[[Germany]]
|1834
|Trademark of the [[Riedel (glass manufacturer)|Riedel wine glass company]] since 2004
|-
|[[Riedel (glass manufacturer)|Riedel wine glass company]]
|[[Austria]]
|1756
|World leading wine glass manufacturer
|-
|[[Swarovski]]
|[[Austria]]
|1895
|Production continued
|-
|[[Ajka crystal]]
|[[Hungary]]<ref name="Fotex Holding">{{cite web
 |url=http://www.fotex.eu/page/companies/ajka 
 |title=FOTEX-group » Ajka Crystal LLC 
 |publisher=Fotex Holding SE Plc 
 |location=Luxembourg, Belgium 
 |access-date=16 August 2012 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20120102020630/http://www.fotex.eu/page/companies/ajka 
 |archive-date= 2 January 2012 
}}</ref>
|1878
|In 1991 opened porcelain studio
|-
|[[Moser (glass company)|Moser]]
|[[Czech Republic]]
|1857
|Production continued
|-
|[[Nižbor glassworks|Rückl]]
|[[Czech Republic]]
|1846
|Production continued
|-
|[[Crystalex]]
|[[Czech Republic]]
|1948
|Production continued
|-
|[[Preciosa (corporation)|Preciosa]]
|[[Czech Republic]]
|1948
|Production continued
|-
|[[Lasvit]]
|[[Czech Republic]]
|2008
|Production continued
|-
|[[Steuben (glass)|Steuben Glass]]
|[[United States]]
|1903
|Sold by [[Corning Incorporated]] to the [[Schottenstein Stores Corp.]] in 2008. In 2008 Schottenstein closed factory
|-
|[[Rogaška]]
|[[Slovenia]]
|1927
|Production continued
|-
|[[Hoya Corporation|Hoya]]
|[[Japan]]
|1945
|Closed in 2009
|-
|[[Mikasa & Company|Mikasa]]
|[[Japan]]
|1970s
|Sold by the [[Arc International]] to [[Lifetime Brands]] in 2008
|-
|[[Liuligongfang]]
|[[Taiwan]]
|1987
|Production continued
|-
|[[Asfour crystal]]
|[[Egypt]]<ref name="ASFOUR Crystal">{{cite web |url=http://www.asfourcrystal.com/about-us |title=ASFOUR crystal » about us |publisher=ASFOUR Crystal international |location=Cairo, Egypt |access-date=9 May 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130501085738/http://www.asfourcrystal.com/about-us |archive-date=1 May 2013 }}</ref>
|1961
|Production continued
|}

==Safety==
Several studies have demonstrated that serving food or drink in glassware containing lead oxide can cause lead to leach into the contents, even when the glassware has not been used for storage.  Due to an inability to "indicate a threshold for the key effects of lead," a 2011 [[World Health Organization]] committee on food additives "concluded that it was not possible to establish a new PTWI (provisional [[tolerable weekly intake]]) that would be considered health protective."<ref>{{Cite web |title=Evaluations of the Joint FAO/WHO Expert Committee on Food Additives (JECFA) |url=https://apps.who.int/food-additives-contaminants-jecfa-database/Home/Chemical/3511 |access-date=2022-07-22 |website=apps.who.int}}</ref><ref name="Leaching1" />

The amount of lead released from lead glass increases with the acidity of the substance being served. Vinegar, for example, has been shown to cause more rapid leaching compared to white wine, as vinegar is more acidic.<ref>{{Cite journal |last=Hight |first=S. C. |date=1996 |title=Lead migration from lead crystal wine glasses |journal=Food Additives and Contaminants |volume=13 |issue=7 |pages=747–765 |doi=10.1080/02652039609374463 |issn=0265-203X |pmid=8885316}}</ref> Citrus juices and other acidic drinks leach lead from crystal as effectively as alcoholic beverages.<ref name="Leaching1">{{cite journal |last1=Guadagnino |first1=E |last2=Gambaro |first2=M |last3=Gramiccioni |first3=L |last4=Denaro |first4=M |last5=Feliciani |first5=R |last6=Baldini |first6=M |last7=Stacchini |first7=P |last8=Giovannangeli |first8=S |last9=Carelli |first9=G |last10=Castellino |first10=N. |last11=Vinci |first11=F. |display-authors=8 |year=2000 |title=Estimation of lead intake from crystalware under conditions of consumer use |journal=Food Additives and Contaminants |volume=17 |issue=3 |pages=205–18 |doi=10.1080/026520300283469 |pmid=10827902 |s2cid=23911153}}</ref><ref name="Leaching2">{{cite journal |last1=Barbee |first1=SJ |last2=Constantine |first2=LA |year=1994 |title=Release of lead from crystal decanters under conditions of normal use |journal=[[Food and Chemical Toxicology]] |volume=32 |issue=3 |pages=285–8 |doi=10.1016/0278-6915(94)90202-X |pmid=8157224}}</ref> Daily usage of lead crystalware (without longer-term storage) was found to add up to 14.5 μg of lead from drinking a 350ml cola beverage.<ref name="Leaching1" />

The amount of lead released into a food or drink increases with the amount of time it stays in the vessel. 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.<ref>{{Cite journal |last1=Appel |first1=B R |last2=Kahlon |first2=J K |last3=Ferguson |first3=J |last4=Quattrone |first4=A J |last5=Book |first5=S A |date=1992 |title=Potential lead exposures from lead crystal decanters. |journal=American Journal of Public Health |volume=82 |issue=12 |pages=1671–1673 |doi=10.2105/ajph.82.12.1671 |issn=0090-0036 |pmc=1694534 |pmid=1456345}}</ref> After two days, lead levels were 89&nbsp;μg/L (micrograms per liter). After four months, lead levels were between 2,000 and 5,000&nbsp;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&nbsp;μg/L.<ref>{{cite journal |doi=10.1016/0140-6736(91)90803-W |title=Lead exposure from lead crystal |year=1991 |last1=Graziano |first1=P |journal=The Lancet |volume=337 |issue=8734 |pages=141–2|pmid=1670790 |s2cid=11508890 |doi-access=free }}</ref>

Lead leaching from the same decanter decreases with repeated uses. This finding is "consistent with ceramic chemistry theory, which predicts that leaching of lead from crystal is self-limiting exponentially as a function of increasing distance from the crystal-liquid interface."<ref name="Leaching2" />

It has been proposed that the historic association of [[gout]] with the upper classes in Europe and America was, in part, caused by the extensive use of lead crystal decanters to store [[fortified wine]]s and [[whisky]].<ref>{{cite book |author=Emsley, John |url=https://archive.org/details/elementsofmurder00emsl |title=Elements of murder |publisher=Oxford University Press |year=2005 |isbn=0-19-280599-1 |url-access=registration}}</ref> Statistical evidence linking gout to [[lead poisoning]] has been published.<ref>{{cite journal |last1=Lin |first1=Ja-Liang |last2=Tan |first2=Dan-Tzu |last3=Ho |first3=Huei-Hong |last4=Yu |first4=Chun-Chen |year=2002 |title=Environmental lead exposure and urate excretion in the general population |journal=The American Journal of Medicine |volume=113 |issue=7 |pages=563–8 |doi=10.1016/S0002-9343(02)01296-2 |pmid=12459402}}</ref>

==See also==
{{Commons category|Crystal glass}}
{{div col|colwidth=22em}}
*[[Steuben (glass)|Steuben Crystal]]
*[[Waterford Crystal]]
*[[Edinburgh Crystal]]
*[[Swarovski]]
*[[Ajka Crystal]]
*[[List of indices of refraction]]
*[[Lead]]
*[[Hot cell]]
*[[Val Saint Lambert]]
{{div col end}}

==References==
{{Reflist}}

==Sources==
* {{cite journal |last1=Deeg |first1=Emil |title=Zusammenhang zwischen Feinbau und mechanisch akustischen Eigenschaften einfacher Silikatgläser|trans-title=Relationship between Fine Structure and Mechanical-Acoustical Properties of Single Silicate Glasses |journal=Glastechnische Berichte | issn=0946-7475 |date=1958 |volume=31 |issue=6 |pages=1-9, 85-93, 124-, 229- |trans-journal=Glass science and technology | language=de | publisher=Deutsche Glastechnische Gesellschaft}}
* {{cite book|last1=Kurkjian|first1=Charles R.|last2=Kieffer|first2=John|title=Handbook of Elastic Properties of Solids, Liquids, and Gases|chapter=Elastic Properties of Glasses|publisher=Elsevier|date=2001|isbn=978-0-12-445760-7|doi=10.1016/b978-012445760-7/50047-2}}
* {{cite book|last=Visser|first=M.|title=The Rituals of Dinner: The Origins, Evolution, Eccentricities, and Meaning of Table Manners|publisher=Open Road Media|year=2015|isbn=978-1-5040-1169-3|url=https://books.google.com/books?id=PQvzCAAAQBAJ&pg=PT220|access-date=2024-11-16| chapter-url=https://books.google.com/books?id=aPmGAwAAQBAJ&pg=RA2-PA5}}

{{Glass science}}

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{{Authority control}}

{{DEFAULTSORT:Lead Glass}}
[[Category:Glass compositions]]
[[Category:Lead(II) compounds]]