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The next operation to be performed is the removal of 

 every particle of oxide or other impurity from the surface 

 of the plates. For this purpose each is bent to an angle 

 of about GO , so as to bring it into the form of an inverted 

 \ or n,.and then steeped^ for a few minutes in a leaden 

 trough containing a weak solution of muriatic acid. Four 

 pounds of acid to three gallons of water makes a mixture 

 of the proper strength, and sufficient for eighteen hundred 

 plates. After being immersed for four or five minutes in 

 this cleansing liquid, the plates are taken out, arranged on 

 the floor in rows, and then removed, by means of an iron 

 rod, to a reverberator}' furnace or oven, in which they are 

 submitted to a red heat. The reason for bending the 

 plates now becomes obvious, because if they were flat, the 

 two sides could not be equally exposed to the flame by 

 which the furnace is heated ; whereas by bending them, and 

 placing them upon their edges, the flame is allowed to 

 play upon both sides. The heat to which the plates are 

 exposed, combined with their previous washing in the acid, 

 causes them to throw off a scale of rust or oxide, whence 

 this operation is termed scaling. If well performed, it 

 gives to the iron a mottled blue and white surface, some- 

 what resembling marbled paper. The plates are then 

 flattened by beating them upon a cast-iron block, and sub- 

 mitted to a second or cold rolling, which removes any 

 warpinir acquired in the previous processes, gives a high 

 degree of smoothness to their surfaces, and imparts elas- 

 ticity to the iron. The rollers, or rolls, employed in this 

 operation are formed of cast-iron, rendered very hard by 

 casting in thick cold iron boxes or moulds, and their sur- 

 faces are carefully polished. Parkes states that rollers of 

 about thirty inches diameter are much better than those of 

 smaller dimensions for this purpose : the length of the rolls 

 .ally seventeen or eighteen inches. After the cold 

 rolling the plates are immersed singly, in a vertical posi- 

 tion, in an acidulous preparation called the ///>*, consisting 

 of water in which bran has been steeped for nine or ten 

 days, until it has fermented and become slightly acid. In 

 this the plates are kept for ten or twelve hours, and occa- 

 sionally turned, to insure an equal exposure of every part 

 of their surface ; and from the lye-trough they are trans- 

 ferred to a leaden vessel containing diluted sulphuric acid, 

 the strength of which is varied according to the judgment 

 of the workman. This trough is divided into compart- 

 ments, which will contain a box of plates each; and both 

 it and the 1;. -trough are slightly heated by flues, to assist 

 the actin of the acid menstrua. Parkes states that a tem- 

 perature of 90" or 100' Fahrenheit is sufficient for this ope- 

 ration, which is called pickling, and which requires some 

 nicety, to prevent the plates from being strained or blis- 

 tered by remaining too long in the acid. They are usually 

 agitated in the weak sulphuric acid for about an hour, 

 until they become bright and free from black spots. They 

 aie then removed into pure water, in which they are 

 scoured with hemp and sand, to remove any remaining 

 oxide; and in this bath of pure water the plates remain 

 until wanted for tinning, because, even if left for months, 

 they will remain perfectly free from rvist. 



As the sole object of these operations is to cleanse the 

 iron plates from rust and dirt, it is evident that the details 

 may be varied considerably ; but it is not necessary to 

 notice particularly any deviations from the usual process. 

 The tinning of the plates is effected in a range of cast- 

 iron pots heated by flues, and forming together an appa- 

 ratus called the stow. The plates are removed one by one 

 from the last-mentioned bath of pure water, and dried by 

 rubbing with bran, after which they are immersed singly 

 iii a pot filled with melted tallow or grease, in which they 

 are left for about an hour. The grease preserves the sur- 

 face from oxidation, and appears also to increase the affi- 

 nity of the iron for tin ; and for this purpose burnt grease, 

 Or any kind of c-mpyreuinaiic fat, is found preferable to 

 pure fresh tallow. From the grease-pot the plates are re- 

 1, wi'h the grease which adheres to their surfaces, 

 into the metallic bath, which contains a mixture of block 

 and grain tin, covered with a quantity of grease sufficient 

 four inches deep. Parkes states that the 

 mixture of block and grain tin usually contains about 

 i of each ; but he conceived that manui'ac- 

 iil tind it advantageous to use grain-tin alone ; 

 sim-t'. although it would be rather more expensive, its 

 .uid fluidity would occasion it to adhere to 

 tut: inm in a thinner film. The tin-bath or pot is heated 

 I'.C., No. - 



to such a degree as almost to inflame the fatty mixture 

 upon the surface of the tin; and its dimensions are such 

 that it will receive two or three hundred plates standing 

 upright on their edges. The precise size is immaterial, so 

 that the number of plates put in is such as to prevent any 

 from falling down ; but it is convenient to make it large 

 enough to hold a box and a half of plates, or about three 

 hundred and forty. When the plates have remained in 

 the tin-bath a sufficient time (usually about an hour and 

 a half, but more for thick plates), they are lifted out with 

 tongs, and placed upon an iron grating, to allow the super- 

 fluous tin to drain off; but as there still remains upon 

 them much more than the proper quantity of tin, they are 

 afterwards subjected to a process called washing, which 

 consists in dipping them into a pot containing a quantity 

 of pure grain-tin in a melted state, then rubbing them 

 with a peculiar kind of brush made of hemp, plunging 

 them again for a moment into the melted tin in the wash- 

 pot, and then into a pot filled with clean melted tallow, or 

 lard free from salt, which contains pins, to prevent the 

 plates from touching each other. The heat of this second 

 tin-bath melts and detaches the superfluous and coarser 

 portions of the tin from the plates, and the drossy impu- 

 rities rise to the surface ; while the other portions unite 

 with the grain-tin, and so deteriorate its quality, that, alter 

 washing sixty or seventy boxes, it becomes necessary to 

 remove about three cwt. of tin from the wash-pot, antf to 

 supply its place by a block of pure grain-tin. The impure 

 tin thus removed from the wash-pot is put into the bath 

 in which the plates receive their first tinning. As it is 

 desirable, in the final dipping of the plate, to preserve it 

 from contact with the dross or scum which collects upon 

 the surface of the bath, a partition is inserted in the wash- 

 pot, to keep one compartment free of scum. The last dip 

 serves to eradicate the marks of the brush, and to replenish 

 the coat of tin wherever it may have been rubbed too thin ; 

 and the subsequent immersion of the plates in the grease- 

 pot causes any superfluous metal to run off. The heat of 

 the tallow-bath, and the period of immersion in it, must 

 be regulated with care. Thick plates require the tallow 

 to be cooler than for thin ones, because they retain mo ( re 

 heat in themselves ; and if a thick plate were placed in a 

 bath of proper temperature for thin plates, it would come 

 out of a yellow instead of a silvery-white colour ; while, 

 on the contrary, a bath intended for thick plates would be 

 too cool to eft'ect the tequired purpose upon thin sheets. 

 Too short a period of immersion has a similar eft'ect, and. 

 leaves too much tin upon the surface, and that in a wavy 

 irregular film ; while if left too long in the grease-pot, the 

 tin would run off to such a degree as to render another 

 dipping necessary. So soon as the workman employed in 

 washing has placed five plates in the grease-pot, a boy lifts 

 the first from it into a draining-pan with a grated bottom ; 

 and when the man has placed the sixth in'the tallow, the 

 boy removes the second. Notwithstanding the apparently 

 complicated character of the operations just described, 

 they are performed so rapidly, that an expert wash-man 

 will wash and brush twenty-five boxes, or five thousand 

 six hundred and twenty-five plates, in twelve hours. 



Owing to the vertical position of the plates during the 

 preceding operations, a selvage of tin accumulates along 

 their lower edge, which is removed by the process called 

 lixtiiig. This is performed by taking the plates one by 

 one, as soon as they are cool enough to handle, and dipping- 

 their lower edges into a pot called the list-pot, or listing- 

 pot, which contains enough melted tin to form a layer a 

 quarter of an inch thick. The selvage of tin being thus 

 melted, is shaken off by a smart blow with a stick, leaving 

 only a faint stripe, which may be discerned upon all 

 finished tin-plates. After listing, the plates are cleaned 

 from grease by rubbing them, while yet warm, with dry 

 bran ; after which they are packed in boxes of wood or 

 sheet-iron. 



The tinning of the inner surfaces of cooking utensils and 

 otln'T vessels of capacity is performed by scouring the sur- 

 face until it is perfectly bright and clean ; then heating- 

 the vessel, pouring in some melted tin and rolling it 

 about, and rubbing the tin all over the surface with a 

 piece of cloth or a handful of tow : powdered rosin is 

 used, as in soldering, to prevent the formation of oxide, 

 which would impair the mutual affinity of the metals. 

 Pure grain-tin should be used for this purpose, but it is 

 frequently adulterated with lead. By this means vessels. 



Vol.. XXIV. 3 Q 



