Charcoal: Charcoal is a solid fuel and the very best fuel for heating purposes. It is free from the impurities mentioned here. It is made by burning hard wood in a closed oven or kiln. This kiln in turn burns the wood into lumps of charcoal. The cost makes the only real objection to the use of charcoal as fuel.
PIG IRON
Iron ore is an oxide of iron containing from 35 per cent. to 65 per cent. iron. The rest is oxygen, phosphorus, sulphur, silica, and other impurities. Iron ore is charged into a blast furnace, mixed with limestone as a flux, and melted down, with coke as fuel. The metal which results from this melting is known as commercial pig iron.
WROUGHT IRON
Wrought iron is made from pig iron. The pig iron is remelted in a so-called puddling furnace by charging about half a ton at one time into the furnace. While in a molten state it is stirred up with large iron hooks by the puddler. It is kept boiling so as to expose every part of the iron bath to the action of the flame in order to burn out the carbon. The other impurities will separate from the iron and run out of the furnace as slag.
The temperature in the puddling furnace is high enough to melt pig iron but not high enough to keep wrought iron in a liquid state. So, as soon as the small particles of iron become purified the partially congealed portion forms a spongy mass, in which small globules of iron ore are in a semi-plastic state. These are gathered up by the puddler and his helper and are formed into a ball on the bottom of the furnace by means of long rabble bars used for this purpose. The ball is about 150 to 200 pounds in weight. These lumps of iron are taken to a large hammer or squeezer.
There they are shaped into long blooms to fit the rolls. They are taken right from the squeezer to the rolling mill and rolled out into bars 4 ins. or 5 ins. wide and 3⁄4 in. thick. These bars are called muck bars owing to their spongy-like appearance and the large quantity of cinders which they contain. The muck bars are now cut into lengths of 3 ft. and 4 ft. and are piled on top of each other in blocks of 200 lbs. The blocks are put into a heating furnace and heated to a welding heat. While at this heat they are put through the rolls, thus welding the whole mass together, at the same time reducing the pile to sizes required by the market. When cold these are cut into lengths for use. This is the iron used in most blacksmiths' shops.