Editing Float glass (section)

== History ==
[[File:windowfloatnofloat.jpg|thumb|Old [[window]] containing a single sheet of float glass in the upper left section, [[Jena]], [[Germany]]. The remaining sections are possibly not float glass as indicated by the distorted reflections of a tree.]]
Until the 16th century, window glass or other [[flat glass]] was generally cut from large discs (or rondels) of [[crown glass (window)|crown glass]]. Larger sheets of glass were made by [[glassblowing|blowing]] large [[Cylinder blown sheet|cylinders]] which were cut open and flattened, then cut into panes. Most window glass in the early 19th century was made using the [[cylinder method]]. The 'cylinders' were {{convert|6|to|8|ft|cm}} long and {{convert|10|to|14|in|cm}} in diameter, limiting the width that panes of glass could be cut, and resulting in windows divided by transoms into rectangular panels.

The first advances in automating glass manufacturing were patented in 1848 by [[Henry Bessemer]].<ref>Bessemer, Henry ; British patent no. 12,101 (issued: Sept. 22, 1848).</ref> His system produced a continuous ribbon of flat glass by forming the ribbon between rollers. This was an expensive process, as the surfaces of the glass needed polishing. If the glass could be set on a perfectly smooth, flat body, like the surface of an open pan of calm liquid, this would reduce costs considerably. Attempts were made, including by Bessemer, to form flat glass on a bath of molten tin—one of the few liquids denser than glass that would be calm at the high temperatures needed to make glass—most notably in the US. Several patents were granted,<ref>{{cite web | url=https://books.google.com/books?id=F6skAQAAMAAJ&q=glass+molten+tin+bessemer | title=The Glass Industry | date=1984 }}</ref><ref>William E. Heal, [http://pdfpiw.uspto.gov/.piw?Docid=00710357&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect2%3DPTO1%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D%2Fnetahtml%2FPTO%2Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526d%3DPALL%2526S1%3D0710357.PN.%2526OS%3DPN%2F710357%2526RS%3DPN%2F710357&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page "Manufacture of window and plate glass,"] {{Webarchive|url=https://web.archive.org/web/20170817210619/http://pdfpiw.uspto.gov/.piw?Docid=00710357&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect2%3DPTO1%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D%2Fnetahtml%2FPTO%2Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526d%3DPALL%2526S1%3D0710357.PN.%2526OS%3DPN%2F710357%2526RS%3DPN%2F710357&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page |date=2017-08-17 }} U.S. patent no. 710,357 (filed:  January 25, 1902; issued: September 30, 1902)</ref><ref>Halbert K. Hitchcock, [http://pdfpiw.uspto.gov/.piw?Docid=00789911&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect2%3DPTO1%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D%2Fnetahtml%2FPTO%2Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526d%3DPALL%2526S1%3D0789911.PN.%2526OS%3DPN%2F789911%2526RS%3DPN%2F789911&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page "Apparatus for manufacturing glass sheets or plates,"] {{Webarchive|url=https://web.archive.org/web/20170817210619/http://pdfpiw.uspto.gov/.piw?Docid=00710357&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect2%3DPTO1%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D%2Fnetahtml%2FPTO%2Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526d%3DPALL%2526S1%3D0710357.PN.%2526OS%3DPN%2F710357%2526RS%3DPN%2F710357&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page |date=2017-08-17 }} U.S. patent no. 789,911 (filed:  July 30, 1902; issued:  May 16, 1905).</ref> but this process was unworkable at the time.

Before the development of float glass, larger sheets of plate glass were made by casting a large puddle of glass on an [[iron]] surface, and then polishing both sides, a costly process. From the early 1920s, a continuous ribbon of plate glass was passed through a lengthy series of inline grinders and polishers, reducing glass losses and cost.<ref>{{Cite web |title=The Double Steal - the Right and Wrong Way to Steal Trade Secrets |url=https://socxfbi.org/SFSA/SFSA/CaseStories/The-Double-Steal---the-Right-and-Wrong-Way-to-Steal-Trade-Secrets.aspx |access-date=2023-04-29 |website=socxfbi.org |language=en}}</ref>

Glass of lower quality, drawn glass, was made by drawing upwards from a pool of molten glass a thin sheet, held at the edges by rollers. As it cooled the rising sheet stiffened and could then be cut. The two surfaces were of lower quality i.e. not as smooth or uniform as those of float glass. This process continued in use for many years after the development of float glass.

Between 1953 and 1957, at the Cowley Hill Works St Helens, Lancashire, Sir [[Alastair Pilkington]] and Kenneth Bickerstaff of the UK's Pilkington Brothers developed the first successful commercial application for forming a continuous ribbon of glass using a molten [[tin]] bath on which the molten glass flows unhindered under the influence of gravity.<ref>{{cite journal | doi = 10.1098/rspa.1969.0212 | title = Review Lecture. The Float Glass Process | first = L. A. B. | last = Pilkington | journal = Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences | volume = 314 | issue = 1516 | pages =  1–25 | jstor =  2416528 | year = 1969 | publisher = The Royal Society| bibcode = 1969RSPSA.314....1P | s2cid = 109981215 }}</ref> The success of this process lay in the careful balance of the volume of glass fed onto the bath, where it was flattened by its own weight.<ref name=floatpatent>[https://patents.google.com/patent/US2911759 US patent 2911759 &ndash; Manufacture of flat glass]</ref> Full scale profitable sales of float glass were first achieved in 1960, and in the 1960s the process was licensed throughout the world, replacing previous production methods.<ref>{{cite journal |last1=Nascimento |first1=Marcio Luis Ferreira |title=Brief history of the flat glass patent – Sixty years of the float process |journal=World Patent Information |date=September 2014 |volume=38 |pages=50–56 |doi=10.1016/j.wpi.2014.04.006 |bibcode=2014WPatI..38...50N |url=https://lamav.ufba.br/pdf/WPI38.pdf}}</ref>