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Lighting the Cupola

Success in cupola-melting depends, to some extent, upon the manner of starting the fire. Carelessness in this particular may result in there being more or less of the fuel in a semi-cold condition lying upon the bottom when the molten iron begins to fall from above. This naturally dulls the iron at the beginning, and may exert a bad effect upon the heat all through. It should be the aim of the cupola-man to have a clear, bright fire upon the bed before the blast is admitted, so that hot fluid metal will show at the first tap. In order to accomplish this, some attention should be paid to the kind of wood used for kindling with, as well as to the manner of distributing it at the bottom of the cupola; short pieces are the best, as they can be arranged with a view to preserving the sand bottom intact; and, whilst it is absolutely necessary to preserve a good free passage for air, yet it is well to prevent, as much as possible, any of the coal or coke from falling to the bottom before it has become thoroughly ignited. If old wood is used, let it be freed from every particle of sand, otherwise a slaggy bottom is the result from the start. Nails, spikes, and other malleable-iron fastenings, usually so plentiful in old foundry chips and lumber, should be carefully extracted before such wood is used for kindling with, as if left in any considerable quantity the nature of the iron is changed for a length of time proportionate to the amount of wrought iron introduced. Dirty kindling-wood and rusty nails have much to answer for at some foundries. Intelligent operation will soon discover just how much wood is needed to thoroughly ignite the coal or coke, so that only enough is used; any addition to this is wilful waste. For igniting coal, more wood will be required than for coke, and a little more time must be allowed for kindling a coal-stock. Whilst it is very important that the bed fuel be thoroughly ignited before the charging begins, it is not by any means a wise method to permit the stock to become white-hot before introducing the first charge of iron; when once it is sure that the fire has spread evenly all through the fuel, and is about to strike through the top, the iron may then be charged. By this means the heat, which in the former case escapes uninterrupted up the stack, is utilized for raising the temperature of the iron charged before it has reached the melting-point, the result being quicker melting and hotter metal. See CUPOLA; HOOD; CHARGING THE COMMON CUPOLA.