The need for artillery required a Foundry with a furnace equipped for casting and two factories where saltpetre and gunpowder were prepared.The furnace of Lucca, when in operation, had much in common with the image handed down in the 1589 fresco by Ludovico Buti which is preserved in the Uffizi Armoury.

The scene shows the working phases: in the centre the stoker stoking the fire, on the left the smelter guides the casting of the bronze that flows into a clay channel to go into the casting pit. In the foreground, on some stands, there are two clay moulds ready to receive the casting. In the background, two workers are finishing the pieces that had already come out of the casting.

The glow of the flames rising from the kiln give the scene a strong suggestive charge
that must have greatly impressed those who witnessed it.