Puddling Steel Mill, Siemens-Martin Steel Mill @museum.de

This is where the second part of our exhibition begins. Here, we trace the sequence of technological processes at the Thale ironworks: from the starting products – the input – to the finished bathtub or enamel cup.

First of all, you had to produce the steel. But though Thale had a furnace for smelting iron ore, there was never a blast furnace for steel production. That’s because producing steel requires a great many raw materials, and those weren’t available in Thale or the surrounding area. So for many decades, Thale was purely a sheet metal works.

It wasn’t until 1874 that Thale started to produce steel by means of what’s known as the puddling process, which turns pig iron into malleable iron suitable for forging. What was unusual in Thale – apart from the late introduction of the process – is that the mill used mainly scrap rather than pig iron. That was mainly due to the raw materials situation. The scrap accumulated anyway here at the works in the form of sheet metal waste, or it was bought in.

If you turn around, you can see a model of the puddling furnace to the left of the doorway. The puddler would have stood at the open work door and stir the liquefied input to reduce the carbon content. Since that increased the melting point, stirring became harder and harder for the puddler.

The temperature at the open work door would have been between a thousand and eleven hundred degrees Celsius, and toxic fumes would also have leaked out. No one could stand being in that kind of environment for long. After 20 minutes, the puddler had to be relieved. Most of them died young.

When a puddler dies, the saying goes, he becomes a stoker at the fires of hell. And he’s better off there.

For a quarter of a century – from 1874 to just short of the turn of the century – forgeable steel was produced in Thale using this process. At that point, there were concerns that the plant would no longer be able to keep pace with new technological developments, or indeed produce quality sheet metal for enamelware.

So they invested in Siemens-Martin technology, also known as the acid open hearth process. This involves pre-heating the air and gas, enabling the furnace to reach the melting point of iron. Using this much more productive process, the specified carbon content could easily be achieved and better grades of steel produced.

The Siemens-Martin process was the main method of steel production at Thale from 1900 to 1984.