FOUNDING; FOUNDRY. 



FOUNDING ; FOUNDRY. 



114 



demand for various object* in meUl was now to greatly increased that 

 it wu evident, first {rum the consumption of timber for the foundries, 

 and next from the destruction of foreaU in consequence of the agricul- 

 tural impruveiuenU which were taking place in various parts of the 

 country, that this provision must soon prove insufficient to meet the 

 wants of the trade. It was then that the attempt was made to bring 

 coal into use; and it is curious at this time to know how much 

 difficulty, first from ignorance of its real value in the operations of 

 metallurgy, and then from prejudice against such an innovation upon 

 the old habit of burning wood only (to which must also be added the 

 interference with the interests of wood monopolists), was thrown in 

 the way of its introduction. One of the earliest and most zealous 

 advocates for its use, Dudley, had all his works destroyed, and was 

 nearly ruined by the violence of his opponents; but at length the 

 employment of coal was fully established ; and from that time the 

 rapid advance of the iron and other metal works of this country may 

 be dated. 



We have stated the chief reason for having recourse to the coal- 

 mines fur fuel to have been the apprehension that the supply of wood 

 fuel would fail. It is important to bear in mind, however, that, but 

 for this well-grounded fear, wood or charcoal would always have been 

 preferred for many of the operations of ^metallurgy ; from its being less 

 objectionable, as regards its chemical composition, than coal. The iron 

 that is smelted in Sweden by wood fuel is considered a superior article, 

 and is much sought after ; and the smelters in this country find it 

 necessary to char or coke the pit and sea-coal which they use, in order 

 to adapt it to the purposes required. [CoKK.] We shall now glance 

 rapidly at some of the operations in the reduction of the ores of the 

 four metals which are produced and worked in the greatest abundance 

 in this country iron, tin, copper, and lead : referring the reader to the 

 articles under the names of those metals for further details. 



Iron L" obtained from a very abundant ore in this country, namely, 

 the common ironstone of our coal-measures. For the reduction of the 

 ore to a metallic state it is necessary to add a certain quantity of lime, 

 which acts as a flux ; and it is worthy of remark that, while the ore 

 itself from which the metal is produced, and the coal for smelting it, 

 are found together, the limestone by which its reduction in facilitated 

 usually abounds in the lower regions of the carboniferous strata. 

 Sometimes, as in the great coal basin of South Wales, a bed of mill- 

 stone grit capable of enduring the fire, and used in constructing the 

 furnaces, is also found in connection or alternating with the iron ore 

 and limestone. The first operation the ore undergoes is roasting. This 

 is done in various ways, both in this and in other countries. Some- 

 times it is conducted in kilns, sometimes on the ground in the 

 open air. The first method is by heaping the iron ore on a mass of 

 ignited coal. In the other, a thick layer of ironstone, broken in pieces, 

 is placed upon a bed of coal, wood, or charcoal (on the continent 

 wood or charcoal is always used), 6 or 8 inches thick, and covering an 

 area of several yards ; upon this another layer of fuel is placed, and 

 then another pile of ore, which diminishes both in area and thickness 

 towards the top. The whole is then covered with small coal or char- 

 coal dust till it reaches some feet above the ground. The lower 

 stratum of fuel is then lighted, and by degrees ignites the whole mass. 

 In the course of a few days the ironstone becomes cool, and the 

 sulphur, arsenic, water, and inflammable matter being driven off, it is 

 fit for smelting. It is then placed in a furnace, with fuel and lime- 

 stone in determined proportions. At Dudley, in Staffordshire, for 

 2J tons of roasted ore, which affords a ton of cast metal, 19 cwt. of 

 transition limestone are employed as flux. In the course of a few 

 hours the whole runs down, and the iron is 'melted, and in that state 

 U allowed to flow into furrows made in sand, where it forms what is 

 termed pig-iron ; or it is poured into moulds where it forms the various 

 articles of cast-iron ware. There are various sorts of cast-iron, but 

 it is usually divided into three classes relatively to its colour and 

 qualities, which are in this country called numbers one, two, three; 

 sometimes more descriptive names are given to the different qualities, 

 as tmooth-faced, gray, white, forge pigi, ballait-iron, Ac., Ac. Cast-iron 

 is converted into 6ar-iron by smelting it by means of charcoal, when 

 it is welded and hammered ; of this there are also varieties, of which 

 the toughest, called <uA-iron, is used in forming fowling-piece barrels. 

 It a made by inclosing old horse-shoe nails tightly in a broad iron 

 ring, generally made of Swedish iron ; a welding heat is then applied, 

 and the whole mass is hammered till by degrees the nails and ring 

 become completely united : it is then drawn into bars, which make an 

 iron of peculiar closeness, toughness, and malleability. These matters 

 are further treated under IRON MANUFACTCBE. 



The best ore of tin is found in Cornwall It is commonly blasted by 

 gunpowder, and is procured in pieces of considerable size, which are 

 tamped to powder by beams shod with iron : it is then well washed 

 till the earthy particles are carried off, and the tin is fit for the smelt- 

 ing house. After being roasted in a reverberatory furnace, and again 

 washed, it i a second time subjected to the furnace, being now mixed 

 with imall coal, and in some cases, with a small quantity of lime. The 

 melted tin thus produced is at last placed in a small furnace and 

 exposed to a very gentle heat, when the purest portion melU first 

 and is drawn off. This is called common grain tin ; and the inferior, 

 which still contain* a small proportion of copper and anenic, i 

 then cast into pigs called Mock f I'M. The finest grain tin is procured 



from the stream works of Cornwall. Good stream tin affords from 

 65 to 75 per cent, of the best jnn'ii. For the details of operation, 

 seeTlx. 



The reduction of copper ore is made by several consecutive pro- 



nea. The first is by calcining it, and when the ore is sufficiently 

 ruattol to oxidate the iron which it contains, it is melted. The 

 melted metal u after a time suffered to flow into a pit filled with 

 water, by which it becomes granulated. It then undergoes further 

 heating, and what U called technically its day (or scoria) is taken off, 

 and it is again allowed to run off into water. After other nearly 

 similar processes the copper is cast in sand, when it becomes solid, and 

 in this state is called blitlfrcd copper. It is now fit for what U termed 

 the refinery, and undergoes an operation called refining or toughening. 

 This is an operation of delicacy, requiring great skill and care in the 

 workmen. The refining is conducted in a furnace similar to tin- 

 melting furnace ; the object U to thoroughly purify the metal from 

 any portions of oxygen, which is performed by adding charcoal to the 

 copper while it is in fusion, and stirring it occasionally till it in judged 

 to be pure. The chemical relations of this process are noticed under 

 COPPER. When tin is united with copper, it forms the compound 

 called bronze. [BRONZE.] 



The greater part of the lead met with in England is procured from 

 a substance called galena,, in which it is found combined with sulphur. 

 There are, however, other ores of lead. The galena, being freed i>\ 

 hammering it and by the hand from whatever impurities can be 

 separated from it by those means, is broken up into small piece- 

 after repeated washings is placed in a reverberatory furnace; but only 

 sufficiently heated to drive off certain ingredients without melting tin- 

 lead itself. The roasting being finished, charcoal is added till the 

 reduction is completed. The lead, after the tlag has been removed 

 from it, is suffered to run out of the furnace into a pan, and being first 

 skimmed is ladled out into moulds and left to cool. There are various 

 methods adopted in different places and under different circumstances 

 for procuring the metal from the ores : these will be found succinrtly 

 noticed under LEAD. 



The furnaces that are used in founding are chiefly of two kinn 

 though strictly speaking both are air furnaces, yet they are distin- 

 guished as air or irhxl furnaces and blast furnaces. The first :< 

 a draught through a chimney ; whereas in the other the air is forced 

 into the body of the furnace by means of bellows. The forms and 

 relative proportions of the different parts of the furnace, and par- 

 ticularly the size, elevation, and direction of the chimnics, ami the 

 dimensions and space of the flues when these are required, are of 

 great importance; the volume and intensity of heat and consequent 

 certainty of the operations depending in a great measure on the know- 

 ledge and science displayed in adapting the parts to each other. The 

 chief points of difference between wind, blast, and reverb* 

 furnaces are described under FURNACE. 



Founding is practised either by melting or casting any quantity of 

 metal in the solid, or with a core (by means of which the metal is 

 preserved of a determined thickness or substance), or in plain casting. 

 Before any object can be cast in metal it is necessary that a model of 

 it be prepared. The models may be made of various substances ; clay 

 or wax, or sand with clay, are those usually employed, but they may 

 also be of wood, stone, or any other material Upon those models 

 moulds must be made ; these are commonly composed of plaster of 

 Paris mixed with brickdust, sometimes sand, or sand with a mixture 

 of cow-hair. For moulds for iron and brass work a yellowish sharp 

 sand is preferred, which is prepared by mixing it with water and then 

 rolling it on a flat board till it is well kneaded and fit for use. This 

 process is called, in technical language, letting. If the model ix 

 cylindrical, or of a form that admits of such a process, it is moulded 

 or cast in two pieces ; these two parts are then carefully joined toge- 

 ther, and the edges or seams trimmed. This doubling is an easy and 

 cheap mode of execution, and only requires care to be successful For 

 the smaller class of works, instead of melting and running the metal 

 at once from a large furnace, earthen crucibles are used, into which 

 the metal is thrown in small pieces : the crucible is placed in a strong 

 heat in a close stove, and as the metal is melted and sinks more is 

 added till the vessel is fulL It is then lifted out by means of iron 

 instruments adapted to the purpose, and the metal is poured from it 

 into the moulds, in which channels or ducts for receiving it have been 

 previously made. There is one great advantage in using crucibles ; 

 namely, that the metal may be carried in them to any part of the 

 foundry, whereas in general it is essential to have the moulds and the 

 furnace close together. It is obvious however that melting metal in 

 crucibles can only be practised where the casting is on a comparatively 

 small scale. 



In noticing the different ways of casting, mention has been made of 

 one in which a core is used, and which may require some explanation. 

 The core, as its name denotes, is a part or portion situated within the 

 body of the cast ; and its purpose in founding is to form a centre to 

 the work by which the thickness or substance of the metal may be 

 regulated. In coring, the mould must first be made complete ; into 

 this, clay or wax, or any other fit substance or material, is then 

 squeezed or pressed in a layer of uniform thickness; in large works it is 

 usually from half an inch to an inch thick. This layer represents the 

 metal. The mould, if in parts, is then to be put together, the above- 



