THE TECHNOLOGIST. [Sept. 1, 1864. 



58 



ON THE MACHINERY FOR THE MANUFACTURE OF PLATE 

 GLASS* 



BY GEOKGE H. DAGLISH, ST. HELEN'S. 



Within the last ten years the production of plate glass in England has 

 been quadrupled, whilst in the same time the price has been diminished 

 fully one-half. The present extent of the manufacture in this country- 

 is about 85,000 square feet per week, whilst about 12,000 square feet 

 per week of foreign plate glass is imported. The foreign glass has ob- 

 tained a preference from its superior lightness of colour, which arises 

 from the greater purity of the materials that it is made of, particularly 

 with regard to the sand, of which the foreign makers have an abundant 

 supply, of great purity and light colour, as seen from the specimens now 

 exhibited of English and foreign sand. 



Under the influence of competition, the English manufacturers have 

 lately commenced an extensive course of experiments with the view of 

 improving the quality of' the plate glass made in this country, and 

 also reducing the cost of manufacture ; and in some instances very 

 decided success has thus far been the result. In order to accomplish 

 these objects, the sand employed at the British Plate Glass Works, at 

 Ravenhead, near St. Helen's, is now imported from France ; and every 

 precaution is adopted to insure as far as possible the chemical purity of 

 the other ingredients of the glass. At these works also two of Mr. 

 Siemens' regenerative gas furnaces have been erected for melting the 

 materials for the plate glass ; and from the absence of smoke and dust 

 in them, and the facilities they afford for regulating the heat, these fur- 

 naces have contributed greatly to the desired results. Under these 

 altered circumstances, the glass now manufactured is fully equal in 

 every respect to the best samples of the French production. 



As time is money, any improvement which tends to expedite the 

 manufacture of glass is of importance. This is strongly exemplified in 

 the process of annealing. After the materials have undergone the pro- 

 cess of melting in the furnace, and are considered in a fit state for casting, 

 the pot containing the melted mass is taken to the casting table, and its 

 contents are poured out on one end of the table in front of a large cast- 

 iron roller ; the material is then spread out over the surface of the table 

 by passing the roller over it, the thickness of the plate of glass being 

 regulated by strips of iron placed along each side of the table, on which 

 the ends of the roller run. As soon as the plate of glass is sufficiently 

 solidified to bear removal, it is introduced into an annealing oven, there 

 to be gradually reduced in temperature or " annealed," until it is fit 

 to be exposed to the atmosphere without risk of fracture. This pro- 

 cess of annealing used formerly to occupy upwards of a fortnight, but 

 from the improved arrangement and construction of the annealing oven 

 it is now completed in four days ; thus three times the quantity of 

 * Read before the Institution of Mechanical Engineers, Birmingham. 



