1016 



TIN-PLATES 



is nearly cold. These sheets are next annealed, and were formerly bent separately by 

 hand, into a saddle, forming two sides of a triangle, thus A, and placed in a reverber- 

 atory furnace, so that the flame should play amongst them, and heat them to redness; 

 they were then plunged into a bath of muriatic acid, or sulphuric acid and water, for 

 a few minutes, taken out, and drained on the floor, and again heated in a furnace ; 

 after which, a scale of oxide of iron separates from the plate during the work of 

 bending them again straight, on a cast-iron block. 



The plates should be now free from rust or scale, and are then passed cold through 

 the chilled rolls : this last process is most important, as the ductility and the strength 

 and colour of the tin-plate depend upon this ; at this point bad iron will crack or 

 split, and any want of quality in the iron, or skill in the manufacture, will be shown. 



A great improvement in the process of annealing was made in 1829 by Mr. Thomas 

 Morgan : the plates were piled on a stand, and covered with a cast-iron box, now 

 termed an ' annealing pot ; ' in this they were exposed to a dull red heat in a reverber- 

 atory furnace for 24 hours. This annealing pot with its stand is represented by 

 Jiff. 2007, in plan and vertical section. 



2007 



A very important invention in the manufacture of iron for tin-plates, was made by 

 Mr. William Daniell in 1845. About 2^ cwts. of refined metal is placed in the char- 

 coal-finery ; this is taken out in one lump, put under the hammer and ' nobbled,' then 

 passed at once through the balling rolls, and reduced to a bar 6 inches square and 

 about 2 feet 6 inches long. This bar is either cut or sawed off 1 in pieces 6 inches long, 

 and these rolled endways to give a bar about 6 inches wide, 2-J- inches thick, and 12 

 inches long, and in this state the inventor calls it ' a billet.' This is heated in a 

 small balling furnace and rolled down to a bar one-quarter inch thick and eleven 

 inches wide, and will be about six feet long. This is taken at once to the tin-plate 

 mill, and the process saves great expense in fuel and machinery. 



By the old method of annealing, a box of tin-plates required about 13 Ibs. of tin. 

 This is now done with about 9 Ibs. for charcoal and 8 Ibs. for coke plates. 



In referring to tin-plates the standard for quotation is always taken as 1 C. 

 (Common, No. 1.) This is a box containing 225 plates, which should weigh exactly 

 112 Ibs. 



The following are-the Marks, Weights, and Measurement of the Tin Plates now in 

 common use : 



