19th century iron and glass architecture: Common construction details of cylinder and crown glass on iron sash bars plate and the iron sash bar. By means of an extensive literature study, this paper gives an overview of the mechanical properties and the construction details of 19th century iron and glass architecture. Before the 18th century, wood, stone and brick were the common building materials. The invention of the puddle furnace in 1783 by Henri Cort made it technically possible to produce wrought iron. In 1817, John Claudius Loudon invented the iron glazing bar. The iron load-bearing frame together with the iron glazing bars made it possible to use glass as a cladding material. Architects and engineers aimed for the most slender iron structures to guide the light through the glazed roofs of typical 19th century building typologies: railway stations, galleries and glasshouses (e.g. the Palm House at Bicton Gardens, Figure 1). Fig. 1: Palm House, Bicton Gardens (UK, 1843) 1 In this study on the common construction details of the connection between cylinder and crown glass on iron sash bars, the invention of the iron glazing bar by John Claudius Loudon is taken as a starting point. The development of industrial processes to produce glass in the beginning of the 20th century was taken as the end point. Nowadays, many of these glass covered structures from the 19th and beginning of the 20th century ask for renovation. The objective of this research is to get a better understanding of the original connection details of the glass 1 Koppelkamm 1981
1. Origin of the iron sash-bar In the international literature about the origin of the 19th century iron and glass building techniques, one reference is nearly always mentioned, namely the Englishmen John Claudius Loudon. He invented the iron sash ousted. Together with the development of steam heating systems, this has lead to a boost in building glasshouses. A very elegant and still existing example of Loudon s framework system is the Palm House in Bicton Gardens at Budleigh Salterton in Devon, UK (Figure 1). bar and published his findings first 2 in The year of construction is not precisely Remarks on the construction of hothouses in known but lies between 1818 and 1843 5. 1817 3 and further more in Sketches of curvilinear hothouses in 1818 4. The iron sash bar has some advantages compared to the previous used wooden sash bars. The main advantages are the small dimensions of the section due to the high strength of the iron and the possibility to bend the sash bar without losing its strength. John Claudius Loudon, as a landscape gardener, focused on the application of his glazing bar in glasshouses. Glasshouses Nowadays, a lot of these buildings need a renovation. When renovating, the question rises whether these constructions need to be strengthened because the slender iron frame mostly does not meet the present-day building codes. The glass can contribute to the overall stiffness of the structure, but then it is important to first understand the used glass in the 19th century and the connection between the glass panes and the iron frame. evolved from the 16th until the 19th century from movable to permanent and from wooden or brick to iron structures. In the end, the wooden sash bars were nearly completely 2 Kohlmaier 1986, 141 3 Loudon 1817 4 Loudon 1818 5 Koppelkamm 1981, 55 and Hix 2005, 30 and Kohlmaier 1986, 104
2. 19th century Belgian course books The building techniques in the 19th century can be studied by analysing the knowledge transfer between professors and students at the Different parameters characterizing the glass and the connection details are recorded (Table 1) from this literature (1847-1919) and will be analysed in the next part of this paper. universities and the technical schools. Van de Vijver lists the structural engineering and construction courses which were given in Belgium from 1780 until 1930 6. His article served as a base for tracking down the most important course books from the 19th century. Another important source consists of the technical handbooks written by architects, engineers, chemists etc. The course books imply this knowledge by cross-references. 3. 19th century glass The two glass types widely spread in the 19th century are crown and cylinder glass. Crown glass is produced by blowing a sphere and turning it around fast so that the ball becomes a plate due to the centrifugal forces. In the second process, a cylinder is blown by the glass blower, which is then cut longitudinally and finally flattened on a table. The result is called cylinder glass. These production The analysed books can be divided in three categories: course books, directly based on processes underwent only little improvements during the considered period. More interesting given courses 7, technical handbooks 8 and was the development of the industrial technical handbooks written by professors and teachers 9 which are the most extensive class and are situated in between the previous two. 6 Van de Vijver 2003 7 Demanet 1847, Demanet 1850, Demanet 1861, Demanet 1862, De Vos 1879, Dechamps 1908 8 Barberot 1888, Moerman 1874 9 Oslet 1888, Combaz 1895, Combaz 1905a, Combaz 1905b, Cloquet 1898, Vierendeel 1902, Francken 1910, Nachtergal 1912, Nachtergal 1919 production of the ingredient soda in 1861 10, leading to more pure and clear glass. The dimensions of a glass plate were limited by the force of the glass blower. Only with a third process, where melted glass was cast on a table, it was possible to produce larger plates. 10 Solvay website, 2009
The glass industry invented accessories to blow bigger glass plates, but the striking improvement only came in the 20th century with the mechanical production processes. In 1900, John Lubbers started the first mechanical blowing and drawing process, in 1905 Emile Fourcault invented a mechanical process of drawing glass directly from the melting pot and in 1919 the first continuous process of casting glass was developed by Max Bicheroux 11. investigated period, but are even in 1919 limited to 1m50 by 1m00 12. In the 19th century, glass was sold by its weight per square meter, which can be roughly translated to the thickness. The glass is classified into three classes: verre simple, verre demi-double and verre double according to the thickness of the glass plate. Since the thickness was mentioned in almost every book it was considered as an important parameter. The definition of these classes varies during the investigated period. The class verre simple 4. Glass as a building material Screening the literature for material characteristics did not lead to the information we need at present when calculating a structure. But the books did provide details about production processes, dimensions, classification and thickness. The investigated literature states that cylinder glass was common used in 19th century in Belgium 7, 8 and 9. The maximum dimensions for crown and cylinder glass increase during the decreases from 2.25 mm thickness in 1847 13 to 1-1.25 mm in 1919 12. The verre demi-double decreases from 3-4 mm in 1888 14 to 2 2.5 mm in 1919 12. However, the thickness of the verre double stays constant over time, namely 3-4 mm (Table 1). An explanation of this evolution might be that, despite they had the technical skills to produce thinner plates, the verre double needed to comply with minimum strength necessary to resist snow loads, hail impacts, etc when used in roof coverings. 11 McGrath 1961 12 Nachtergal 1919 13 Demanet 1847 14 Barberot 1888
7, 8 and 9 Table 1: Thickness of glass plates mentioned in Belgian literature 1847-1919 5. Connection details The investigated literature does not provide detailed information about the glass properties, but the connection details between iron and glass are widely covered. The longitudinal connection (the connection between two glass plates) and the transverse connection (the connection between an iron glazing bar and a Fig. 2: Transverse and longitudinal connection of a glass roof glass plate) are considered successively (Figure 2).
There are three construction methods to realize the longitudinal connection. In some books, a system -similar to a slate covering- with a zinc hook is described. The upper glass plate is connected to the lower glass plate via a zinc hook, to keep it in position (Figure 3 top). The second system prevents the upper glass plate from sliding down by positioning a pin at the end of the glass plate through the web of the The gap between the two glass plates can be filled with putty or it can stay open. The two systems are mentioned scattered in the course books and technical handbooks, without any pattern or evolution in time. A third possibility is to only count on the transverse connection to hold the glass panes in position, but the literature does not give more details about that alternative. glazing bar (Figure 3 bottom). Figure 3: Zinc hook (top) or putty and a locking pin (bottom) for the longitudinal connection Figure 4: Simple T-section (top), T-section with gutters (middle) and profile system with rubber strips (bottom)
The construction detail of the transverse connection can be divided in two main categories: connections with or without putty. For the connections without putty, special not lifted from the sash bar by wind (which is called the solidarity of the glass panes with the sash bar). The simple T-section is mentioned in the course books and technical handbooks section systems were developed (Figure 4 bottom), called patent glazing. A covering section is screwed on an iron base section. The starting from 1888 14 gutters from 1898 15. and the T-section with contact between the glass and the iron is avoided by using rubber or cotton strips. These strips ensure the water tightness of the connection. The application of these patent glazing systems was rather limited in Belgium and will not be further discussed in this paper. 6. The built structures The course books and technical handbooks describe the knowledge that is transferred to students, architects, engineers, etc. To check whether the used building techniques correspond to literature, important Belgian iron and glass roofs were analysed, listed The transverse connection with putty is characterized by the iron sash bar and the connection with the glass panes. The glass panes can be put on a simple T-section or on a more sophisticated version with gutters (Figure 4 top and middle). The gutters were added to drain away the condensation which originates on the inside of the iron glazing below: Saint-Hubertus galleries, Brussels, by arch. J.-P. Cluysenaar in 1847 (arcade type) Victoria Regia House, Brussels, by arch. A. Balat in 1857 (conservatory type) Winter Garden of the Royal Glasshouses, Laeken, by arch. A. Balat in 1874 (conservatory type) bars. A locking pin could be put through the web of the glazing bar to be sure the glass is 15 Cloquet 1898
Congo House of the Royal Glasshouses, Laeken, by arch. A. Balat in 1886 (conservatory type) Banquet House of the Royal Glasshouses, Laeken, by arch. A. Balat in 1893 (event room type) Maquet House of the Royal Glasshouses, Laeken, by arch. H. Maquet in 1902 (conservatory type) In all these buildings, the simple or decorative T-sections are applied. Neither the locking pins through the web of the glazing bars nor the zinc hooks in the longitudinal connection can be found. The application of the described building techniques in the course books and technical handbooks is thus limited to the simplest techniques: a section where it is easy to put a glass plate on and seal it with putty. Theatre House of the Royal Glasshouses, Laeken, by arch. Ch. Girault in 1905 (event room type) Figure 5: Applied connections at the Saint-Hubertus galleries (1847, Brussels, Cluysenaar) left: overview; middle: transverse and longitudinal connection details; right: renovation campaign and old glass cover (A.2R.C website, 2008)
In this paper, we describe one particular case. The Saint-Hubertus galleries in the centre of Brussels were built in 1847 by architect J.-P. Cluysenaar. A recent renovation campaign was carried out by A.2R.C. architects 16. The original glazing bar was composed of a flat iron bar and two angle sections (Figure 5 middle top). The glass was placed on the hook sections and sealed with putty. In the longitudinal direction (Figure 5 middle bottom), no additional measures were taken to hold the glass plate in position. The overlap between the two glass plates stayed open. double was mainly used for glass roofs. These glass plates had a thickness of 3 to 4 mm and this definition of verre double stayed the same during the investigated period (1847-1919). Different forms of iron sash bars were described in the course books and technical hand books from the 19th century, but they didn t find use in the built structures. When examining executed iron and glass roofs, it is clear that mainly the most elementary building techniques were used in practice. Most structures were built with iron sash bars designed as simple T-sections carrying glass plates with a thickness of 3 to 4 mm. 7. Conclusion In 1817, John Claudius Loudon invented the iron glazing bar. From that date on, the iron and glass architecture became widely spread. 8. Acknowledgements This research is funded by the Institute for the Promotion of Innovation by Science and Technology in Flanders (IWT-Vlaanderen). In the 19th century, glass plates were classified not by their strength but by their weight per square meters or their equivalent thickness. The different classes were named verre simple, verre demi-double and verre double. The verre 16 A.2R.C 1996
9. References A.2R.C, 17/03/2008. Galeries royales Saint- Hubert. www.a2rc.be/a2rc.html. A.2R.C, 1996. Restauratiedossier Sint- Hubertus galerijen. unpublished documents at Dienst Monumenten en Landschappen van het Brussels Hoofdstedelijk Gewest. Barberot, E., 1888. Traité pratique de serrurerie. Liège et Paris, Librairie polytechnique Baudry et Cie. Cloquet, L., 1898. Traité d'architecture, Vol 2. Liège et Paris, Baudry et Cie. Combaz, P., 1895. La construction, Vol 1-2. Bruxelles, E. Lyon-Claesen. Combaz, P., 1905a. La construction, Vol 3-6. Bruxelles, J.-G. Pieper. Combaz, P., 1905b. La construction, Vol 3-7. Bruxelles J.-G. Pieper. De Vos, N., 1879. Cours de construction, Vol 2. Bruxelles, Imprimerie Adolphe Mertens. Dechamps, H., 1908. Les principes de la construction des charpentes métalliques. Liège et Paris, Baudry et Cie. Demanet, A., 1847. Cours de construction. Bruxelles, Wahlen. Demanet, A., 1850. Cours de construction. Bruxelles, Delevigne et Callewaert. Demanet, A., 1861. Cours de construction. Paris, E. Lacroix. Demanet, A., 1862. Cours de construction, Vol 2. Paris, E. Lacroix. Francken, D., 1910. La construction civile. Anvers, A. De Koninckx. Hix, J., 2005. The glasshouse. London, Phaidon Press. Kohlmaier, G., and Von Sartory, B., 1991. Houses of glass: a nineteenth-century building type. Cambridge, MIT. Koppelkamm, S., 1981. Glasshouses and wintergardens of the nineteenth century. London, Granada. Loudon, J.C., 1817. Remarks on the construction of hothouses. London, Taylor. Loudon, J.C., 1818. Sketches of curvilinear hothouses, London. McGrath, R., 1961. Glass in architecture and decoration. London, The architectural press.
Moerman, C., 1874. Traité des constructions civiles. Bruxelles, Mertens. Nachtergal, A., 1912. Charpentes métalliques, Vol 1. Morlanwelz, Adam. Nachtergal, A., 1919. Agenda du bâtiment. Bruxelles, A. Bieleveld. Oslet, G., 1888. Traité de charpente en fer, Vol 4. Paris, Fanchon et Artus. Solvay, 28/12/2009. History Ernest Solvay. www.solvay.com/about/history/ernestsolvay/0,,10502-2-0,00.htm. Van de Vijver, D., 2003. From Nieuport to Magnel: an institutional history of building science in Belgium, 1780-1930 in First International Congress on Construction History. (Madrid) Instituto Juan de Herrera, pp. 2055-2063. Vierendeel, A., 1902. La construction architecturale en fonte, fer et acier. Louvain, A. Uystpruyst.