sentences:  Young's experience of firing ceramics, together with his familiarity with the region as a local surveyor and his amateur interests in geology enabled him to conceive of a heat-proof, blast-furnace brick, using silica found in large deposits at the head of the Neath Valley.The process of "vitrifying" the walls of a ceramic brick-built furnace had been patented by William Harry, of the Swansea Valley in 1817, but Young's solution was to build the whole furnace from a "silica firebrick," made with a 1% addition of lime, to bind the blue-grey "clay" of the Dinas rock.The idea being that the interior of the blast furnace would vitrify and be vastly more durable and ultimately economical, than a mere veneer of silica within a comparatively fragile ceramic shell.