Pud′dling.
1. (Metallurgy.) a. The lining of the hearth or boshes of a furnace in which metal is melted. The material of the puddle was formerly, for some uses, of clay and charcoal worked into a plastic condition. The term puddling has arisen from the fact that the hearth was originally made by a puddling of clay upon the bricks or masonry of the furnace. The clay is now superseded by a fixing of ore, cinder, and scrap, which is banked up around the boshes to protect them from the heat. It is known as fettling in some parts of England. See fixing. b. The process of converting cast into wrought iron by boiling and stirring in connection with the decarbonizing action of the atmosphere which passes through the furnace. Contact between the metal and solid fuel is thereby avoided. The process was invented and brought into extensive use by Henry Cort, and patented in 1784. Cort also invented the puddle-rolls, by which the bloom resulting from a preliminary forging of the loop is drawn out into bars, instead of being extended under the hammer; this Cort patented in 1783. In each case Cort does not seem to have been the first inventor, though he was the most successful and meritorious. He was ruined by the chicanery of partners and government officials, and died poor. Several acts of Parliament, and government grants of small amount, were made to his descendants, even as late as 1856. The puddle-rolls patented by Cort in 1783 are described in Payne's patent, 1728. The process of puddling iron in a reverberating furnace, stirring, gathering the loop, hammering, and rolling, is described in the specification of the Brothers Cranage, 1766, and the furnace in Onion's patent, 1783. The pig-iron, broken into pieces and mixed with a certain proportion of hammer-slag, is put into the furnace, and in the course of 35 or 40 minutes is melted. During this time it has to be constantly stirred with the rabble; the pieces, as they soften, being broken finer, until at last the mass melts and passes to the boiling stage. At this point the severer part of the puddler's work commences. The rabble must be quickly and violently moved throughout the whole charge to promote ebullition. After a while the metal gets thick or pasty, and offers greater resistance to the tool, which is worked from side to side of the furnace, to separate the tough mass into portions. This stage is called coming to nature, and is that in which the pig, deprived for the most part of its silicon and carbon, passes to a purer form, as wrought-iron, requiring only compression to expel the slag and consolidate its particles, and rolling or hammering into merchantable shape, to fit it for use or market. Preparatory to these last-indicated operations, the balls, into which the puddler has separated the pasty mass, are taken out and subjected to the hammer or squeezer, which condenses them into blooms that pass to the rolling-mill. The whole time occupied in the puddling is about an hour and a half. See Pud-Dling-furnace.
2. (Hydraulic Engineering.) Working plastic clay behind sheet-piling, in a coffer-dam, a wall in a dike, the lining for a canal, or in other situation, to resist the penetration of water; generally as supplementary to a main structure and forming a retentive stratum or clothing therefor.
