The Derby Museum version is of a blacksmith's shop where three men work to manufacture an iron or steel component.

Beneath the image of the ingot and hidden by layers of both yellow and white investigators found a small piece of gold leaf that Wright had placed there two centuries before.

[3] Later versions which involve a forge rather than a blacksmith's more traditional way of working are now in the Hermitage Museum in St Petersburg and in The Tate in London.

[4] In 1772, Wright created a 44 by 52-inch variation on this theme called The Iron Forge which was sold to Lord Palmerston for 200 pounds.

An Iron Forge develops the idea of blacksmith's shop which is a craft that has changed little on hundreds of years.

[6] The 1771 painting was bought by the ArtFund and Derby Museum and Art Gallery in 1979 for approximately 69,000 pounds from the Greg family who had owned it since 1875.