Lute, a composition of certain viscid or tenacious matters, which becomes solid, when dry; and which, on being applied to the junctures of vessels, closes them 50 effectually as to prevent the admission or egress of air.
Though lute is chiefly used by chemists, it also comprehends any species of cement, applied to vessels, or furnaces, which are exposed to an ardent heat. It is variously prepared of rye-flour and water; quick-lime and the whites pf eggs 5 iron filings, brick dust, and linseed-oil; potters' earth, ri-ver-sand, horse-dung, pulverized glass, or flocks of wool mixed with salt-water, or bullocks' blood. The best lute, however, and which is most easily procured in London, is Windsor-loam : it should be moderately stiff, so that, when moistened with water, it may be pressed into the side, or crevices, of the furnace, etc. As soon as the clay begins to dry, it must be beaten closely down to the sides, and the fissures repeatedly filled up, till the whole be perfectly closed.
The late Dr. Black recommended a simple mixture of sand and clay, as preferable to any other composition. The proportions for resisting the violence of fire are four parts of sand to one of clay but, if the lute be intended for lining or coating furnaces, he directs six parts of sand to be taken to one of clay, in order that the contraction of the latter may be effectually prevented. This compound is to be applied in a manner similar to that above stated, but it must be allowed to dry for a considerable time ; after which a fire may be kindled, and the furnace gradually heated for one or two days. The heat - should then be raised to the highest degree of intensity, by which the luting will acquire the hardness of free-stone, and afterwards be as durable as any other part of the furnace.