The Herschel home in Slough became a scramble of "labourers and workmen, smiths and carpenters". A 40-foot telescope tube had to be cast of iron. The tube was large enough to walk through. Mirror blanks were poured from Speculum metal, a mix of copper and tin. They were almost four feet (1.2 m) in diameter and weighed 1,000 pounds (454 kg). When the first disk deformed due to its weight, a second thicker one was made with a higher content of copper. The mirrors had to be hand-polished, a painstaking process. A mirror was repeatedly put into the telescope and removed again to ensure that it was properly formed. When a mirror deformed or tarnished, it had to be removed, repolished and replaced in the apparatus. A huge rotating platform was built to support the telescope, enabling it to be repositioned by assistants as a sweep progressed. A platform near the top of the tube enabled the viewer to look down into the tube and view the resulting image.