by popular television presenter Adam Hart-Davis
The Bristol Plumber who dreamed of a way of making lead-shot
William Watts was a tradesman-plumber who lived on Redcliff Hill in Bristol. One night in 1782, on his way home from the pub “having had much ale”, he suddenly felt like taking a little rest by St. Mary Redcliff Church, and went to sleep. As he lay there, he dreamed that his wife was pouring molten lead on him from the church tower, and that as it fell it turned into beautiful round balls. He woke to find that it was only the rain pouring onto his face. However, he was so excited by the idea of the lead balls that he woke his wife to tell her about it, and the next day they tried an experiment together.
They took a rusty old frying pan, climbed up the narrow spiral staircase onto the roof of St. Mary’s, and melted some lead. Presumably they lit a fire to do this, but the roof is covered with lead, so perhaps he had already been up there to repair it. They poured the molten lead through the holes in the bottom of the old frying pan. Sure enough, they found that when they got down that it had landed on the ground as lead-shot.
Shot had previously been made by moulding, which was slow and inefficient. Clearly to mould small spheres is extremely difficult, and as a result all lead-shot was irregular in shape and rather expensive. Watts got a patent on 10th December 1782 for “Making small shot solid throughout, perfectly Globular in form, and without Dimples, Scratches, and other imperfections which other shot theretofore manufactured usually had on their surface”.
Regular as Shot Work
Watts built a 30-foot tower on top of his house, after removing part of the roof, cut a big hole in his bedroom floor and another in his drawing room floor, and dug a pit 35 feet below his cellar. This gave him a total drop of about 90 feet.
When a thin stream of any liquid is poured (e.g., water from a tap) the stream stretches under the influence of gravity, and then breaks up into droplets, which rapidly become perfectly spherical because of surface tension. The important thing about lead-shot is that it should freeze solid before it hits the ground. This takes between two and three seconds, according to the size of the shot. In two seconds it falls about sixty feet (20m), and in three seconds about140 feet (45m). So, Watts’s tower allowed him to make shot up to about 2mm in diameter; for lager shot, modern towers use a drop of around 140 feet. As soon as he had modified his house, Watts began pouring lead-shot, and made a lot of money.
He was given the Freedom of the City of Bristol, and was summoned to Windsor Castle to show his shot to King George III. The King is reputed to have said “I wish all my soldiers were as regular as your shot!” He presented Watts with three plates and a punch bowl of Kien Lung china. A couple of years later Watts decided to change tack, and sold his shot business for £10,000 – a small fortune in those days. Unfortunately he invested his money in trying to build houses just below where the suspension bridge now stands on Windsor Terrace – now known locally as Watts’ Folly. The ground was so treacherous, and the economic situation so precarious because of the Napoleonic wars, that Watts used all his money before the foundations were complete, and went bankrupt in 1794.
However, his idea lives on. Watts’s shot tower was the first in the world, and shot was made there until 1968, by which time the tower was most unsafe – apart from anything else it was leaning more than a foot – and the council pulled it down to widen the road. The company then was Sheldon Bush & Patent Shot Company, who built a new tower in Cheese Lane in 1969, although it is no longer in use.
The process of pouring shot has scarcely changed in 200 years. Today, shot pourers take a steel frying pan, drill holes in the bottom, and pour lead at 375°C. Watts was lucky, his lead came from the Mendip Hills and contains a significant percentage of arsenic, which increases the surface tension, and helps the drops to form. Today, the lead needs additives, but essentially Lead-shot is still made by the method dreamed up by Bristol plumber William Watts in 1782!
To find out more about Adam visit:
Watts's Tower in Cheese Lane
St. Mary Redcliff