TIN-PLATES 



1011 



dip them in the melted tin. About 1747 the plates were, after being cold-rolled, 

 soaked for a week in the lees of bran, which had been allowed to stand in water 

 about ten days, to become, by fermentation sufficiently acid, and then scoured with 

 sand aud water. In 1760 the plates were pickled in dilute hydrochloric acid before 

 annealing, and cleaned with dilute sulphuric acid after being taken out of the bran 

 lees. An improvement of great importance in this process was made about 1745 ; tho 

 inventor seems to have been Mr. Mosely, who carried on tin-plate works in South 

 Staffordshire. This invention was the use of the grease-pot, and in this department 

 little, if any, improvement has since been made. The plan was introduced into 

 South Wales in 1747 by Mr. John Jenkins, and his descendants are still amongst 

 the principal manufacturers in the trade. The process of cleaning and tinning at some 

 of the best works now is as follows : When the sheet iron leaves the plate-mill, and 

 after separating the plates, and sprinkling between each plate a little sawdust, the 

 effect of which is to keep them separate, they are then immersed, or as technically 

 termed ' pickled,' in dilute sulphuric acid, and after this placed in the annealing-pot, 

 and left in the furnace about 24 hours ; on coming out, the plates are passed through 

 the cold rolls ; after passing the cold rolls, the plates seem to have too much the 

 character of steel, and are not sufficiently ductile : to remedy this they are again an- 

 nealed at a low heat, washed in dilute sulphuric acid, to remove any scale of oxide of 

 iron, and scoured with sand and water ; the plates in this state require to be perfectly 

 clean and bright, and may be left for months immersed in pure water without rust or 

 injury ; but a few minutes' exposure to the air rusts them. With great care to have 

 them perfectly clean, they are taken to the stow, fig. 1993, being a section through the 

 line K K of the plan fig. 1994. Taken from right to left, 1 represents the tinman's 

 pan ; 2, the tin-pot ; 3, the washing or dipping pot; 4, the grease-pot ; 5, the cold pot ; 

 6, the list pot. 



1993 

 6543 21 



1994 



The tinman's pan is full of melted grease : in this the plates are immersed, and left 

 there until all aqueous moisture upon them is evaporated, and they are completely 

 covered with the grease ; from this they are taken to the tin-pot, and there plunged 

 into a bath of melted tin, which is covered with grease ; bxit as in this first dipping 

 the alloy is imperfect, and the surface not uniformly covered, the plates are removed 

 to the dipping or wash pot ; this contains a bath of melted tin covered with grease, 

 and is divided into two compartments. In the larger compartment the plates are 

 plunged, and left sufficiently long to make tho alloy complete, and to separate any 

 superfluous tin which may have adhered to the surface ; the workman takes the plate 

 and places it on the table marked B on the plan and wipes it on both sides with a 

 brush of hemp ; then to take away the marks of tho brush, and give a polish to the 

 surface, he dips it in the second compartment of the washing pot. This last always 

 contains the purest tin, and as it becomes alloyed with the iron it is removed on to the 

 first compartment, and after to the tin-pot. The plate is now removed to the grease- 

 pot (No. 4) ; this is filled with melted grease, and requires very skilful management 

 as to the temperature it is to be kept at. The true object is to allow any superfluous 

 tin to run off, and to prevent the alloy on the surface of the iron plate cooling 



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