Brief history of the flat glass patent e Sixty years of the float process Marcio Luis Ferreira Nascimento a, b a Vitreous Materials Lab, Institute of Humanities, Arts and Sciences, Federal University of Bahia, Rua Barão de Jeremoabo s/n, Idioms Center Pavilion (PAF IV), Ondina University Campus, 40170-115 Salvador, Bahia, Brazil b PROTEC/PEI e Postgraduate Program in Industrial Engineering, Department of Chemical Engineering, Polytechnic School, Federal University of Bahia, Rua Aristides Novis 2, Federação, 40210-630 Salvador, Bahia, Brazil article info Article history: Available online 4 July 2014 Keywords: Glass Flat Float Patent History Technology Pilkington abstract This paper deals with one of the single most important innovations made in Great Britain since World War II. It is certainly one of the greatest process inventions of the twentieth century. The float process is one of the most widely used methods for flat glass manufacturing as it ensures security, high quality and productivity. From a historical point this innovation was the beginning of a revolutionary change in the mass production of flat glass for the building and automotive sectors. More specifically this innovation eliminates the traditional operations of rolling, grinding and polishing the glass surface while creating a high quality and inexpensive flat glass product. The first patent was applied for on December 10th, 1953 by Pilkington and Bickerstaff. This paper presents a brief discussion from the 1960s in a historical perspective about this amazing discovery and the main patents related to it. More than 23,900 patents using the term “flat glass” have been filed around the world, according to the European Patent Office databases. These numbers just continue to grow as do total sales worldwide. Looking for titles using flat glass, we found 2,409 patents filed. Curiously, for the same period 1,131 patents were published with float glass in the title and just 3,995 with the term in the title or abstract. So, statistically, there are more published patents using the term ‘flat’ than ‘float’ glass process. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction From the stained glass windows of medieval churches to the Renaissance monopoly of Venetian mirror makers, flat glass has brought us protection from our environment, while also reflecting its beauty. As pointed out by Bricknell, “the prime quality of glass is that it ‘seems’ invisible. The less you are conscious of the glass itself (rather than its color or coating), in a window, a car windscreen or a mirror, the more valuable it is” [1]. Through the ages there have been two basic methods of forming flat glass: the window glass and the plate glass processes [2]. For centuries flat glass has been produced by blowing or by casting. In fact, the very first flat glass process was patented in March 22nd, 1848 by the English engineer Henry Bessemer (1813e1898) under number 12,101. Fig. 1 presents the manufacturing of Bessemer’s process [3]. He was the first to attempt a continuous ribbon of flat glass by forming the ribbon between rollers, but it was not commercially successful. He also made some improvements to such a process which was published on the 17th February 1848 [4]. Float glass was later patented in the United States by two Americans: William E. Heal in 1902 e US patent 710,357 [5], and again in 1925 by Halbert Hitchcock e US patent 1,564,240 [6]. In the early 1900’s, Emile Fourcault (1862e1919) [7,8] in Belgium and independently Irving Colburn (1861e 1917) [9] in the USA invented the technique of producing a continuous ribbon of glass which still involved the glass being drawn through cooled rollers to produce a ‘fire-finished’ product. Briefly, in the Fourcault process [8] the glass was drawn vertically in a ribbon from a bath of molten glass. The final glass surface was achieved by letting the glass surface cool down on its own without contact while still soft. However, some distortions, irregularities and inhomogeneities suitable to this particular process would appear, mainly as the result of small dif- ferences in viscosity due to chemical or even thermal variations. The main goal of glass i.e. to be flawless, perfectly flat, totally uni- form, and free from any distortion or contamination was not reached by these old processes. Up to the early 1950s before the advent of the float process, perfect results were rare and very expensive. Pilkington reported glass wastage amounting to 20% of total production at the time [2]. Sir Alastair Pilkington was born Lionel Alexander Bethune Pil- kington (1920e1995) in Calcutta, India, where his father was employed at the time. According to the New York Times (NYT) E-mail address: mlfn@ufba.br. URL: http://www.lamav.ufba.br, http://www.protec.ufba.br Contents lists available at ScienceDirect World Patent Information journal homepage: www.elsevier.com/locate/worpatin http://dx.doi.org/10.1016/j.wpi.2014.04.006 0172-2190/Ó 2014 Elsevier Ltd. All rights reserved. World Patent Information 38 (2014) 50e56