At five in the afternoon on the twenty-third day, the first full-scale high-pressure inflation test began in the cooperage yard. The twelve-foot flexible reed sleeve had been clamped between two cast-iron test flanges mounted on heavy ash baulks, connected to a double-acting hand force pump manned by four muscular draymen.
To simulate the real conditions of the Sluice Crown vault, the pump drew warm river water from the boiler discharge line at thirty-four degrees. The draymen worked the long pump levers with slow. Then, rhythmic strokes, the water rushed into the dry sleeve with a hollow, bubbling gurgle.
Pella knelt on the wet flat stone slabs, holding her brass measuring tongs over the central outer rim. Under the pressure, the dry reed canvas stiffened instantly. The split reed ribbons swelled as they absorbed the moisture, locking together in their herringbone weave. Meanwhile, the hot pine pitch seeped through the fibers, sealing every needle hole with a shiny, black glaze.
‘Pressure reading twenty pounds,’ Eren Tal called out, tapping the dial of Ada’s Bourdon gauge. ‘Pipe rim seals are bone dry. Not a drop weeping from the bolt holes.’
‘Take it to thirty-five!’ Pella instructed. The draymen heaved on the levers. The sleeve swelled to its full twenty-four-inch width. It hummed with a low, vibrant shaking as the water circulated inside like blood through a huge artery.
