Editing Glass (section)

==== Lead glass ====
{{Main|Lead glass}}{{See also|Lead poisoning}}
The addition of [[lead(II) oxide]] into silicate glass lowers the melting point and [[viscosity]] of the melt.<ref>{{Cite book |url=https://books.google.com/books?id=ZeF_QLW6-xsC&pg=PA125 |title=Introduction to Glass Science and Technology |last=Shelby |first=J.E. |year=2017 |page=125 |publisher=Royal Society of Chemistry |isbn=978-0-85404-639-3}}</ref> The high density of lead glass (silica + lead oxide (PbO) + potassium oxide (K<sub>2</sub>O) + soda (Na<sub>2</sub>O) + zinc oxide (ZnO) + alumina) results in a high electron density, and hence high refractive index, making the look of glassware more brilliant and causing noticeably more [[specular reflection]] and increased [[Dispersion (optics)|optical dispersion]].<ref name="Chawla93" /><ref name="Schwartz-2002">{{Cite book |url=https://books.google.com/books?id=0ETMBQAAQBAJ&pg=PA352 |title=Encyclopedia of Materials, Parts and Finishes |edition=Second |last=Schwartz |first=Mel |year=2002 |page =352 |publisher=CRC Press |isbn=978-1-4200-1716-8}}</ref> Lead glass has a high elasticity, making the glassware more workable and giving rise to a clear "ring" sound when struck. However, lead glass cannot withstand high temperatures well.<ref name="Seafriends-1994" /> Lead oxide also facilitates the solubility of other metal oxides and is used in coloured glass. The viscosity decrease of lead glass melt is very significant (roughly 100 times in comparison with soda glass); this allows easier removal of bubbles and working at lower temperatures, hence its frequent use as an additive in [[vitreous enamel]]s and [[glass solder]]s. The high [[ionic radius]] of the Pb<sup>2+</sup> ion renders it highly immobile 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>&nbsp;Ω⋅cm, [[direct current|DC]] at 250&nbsp;°C).<ref>{{Cite book|url=https://books.google.com/books?id=ASIYuNCp81YC&pg=PA158|title=Ceramic and Glass Materials: Structure, Properties and Processing|last1=Shackelford|first1=James F.|last2=Doremus|first2=Robert H.|date=2008-04-12|publisher=Springer Science & Business Media|isbn=978-0-387-73362-3 |page=158}}</ref>