The installation of the “scrubbing” equipment seemed to improve things at first, but the experiments involving condenser technology were inconclusive. In the early 1860s, the company decided that the effort to clean up the smoke from the factories was too expensive, and it was halted. The pollution problems had not gone away in the meantime, but the company took the position that the money it had spent attempting to clean them up was a sufficient response.

Around the beginning of the 20^th century, various kinds of filters for the recapture of particulate matter came into general use. They operated using the same principles as condensation technology, although the logic was different. The filters were supposed to allow the smoke to escape while recapturing the metals (lead, cadmium and arsenic) which now had a market value when recovered. Vieille-Montagne wanted to recapture them in order to make money. The zinc factories were now seen as production operations for other non-ferrous metals. The zinc industry was transformed into the non-ferrous metals industry. Every time the recapture technology was improved, and the amount of non-ferrous metal recaptured was increased, the pollution associated with zinc production was also decreased, so at one point the company had a direct interest in improving the anti-pollution technology.

Closing Saint-Léonard

As the 19^th century drew to a close, the zinc industry gradually left behind the area of Saint-Léonard and sought other locations in the area of the Albert Canal. New factories were constructed in the Belgian Province of Limburg, the Campine region and the Province of Antwerp. Two reasons explained this migration away from the Province of Liège. On one hand, the mine at La Calamine had proven to be exhausted as early as 1885. Zinc in mineral form now had to be transported to the factory, so it was advantageous for the factories relocated closer to the port of Antwerp, where the mineral could be offloaded. Moreover, for an industry that was far from having resolved its pollution problems, the plain of Campine presented several advantages: it had little value as farmland, there were few people living in the area and it was close to the Albert Canal. A number of high-pollution industries built factories there as of the end of the 19th century.

The industrial site at Saint-Léonard was closed by Vieille-Montagne in the 1880s. Its fate had been decided long ago; the decision to close the plant had been made ten years earlier, as a result of several factors. The conflict with the local population and the authorities had limited the industry’s ability to grow as its owners wished. There were too many private issues involved in Saint-Léonard. Numerous regulations now governed the operation of the factory and prevented it from being run properly (from the viewpoint of the owners). In such a context, investment in Vielle-Montagne began to dry up in the late 1860s, so that Saint-Léonard was in fact the worst performer in its industrial group. The factory was receiving the worst ore and the worst coal; its ovens were never repaired, and when workers quit or retired, they were not replaced. During a period of economic depression, the plant at Saint-Léonard had no utility.

The closing of Saint-Léonard was not the end of the zinc industry in Belgium or in the Province of Liège. In 1930, about a dozen factories were still operating in the Province. After the Second World War, only Flône and Angleur remained. Today Angleur is the last remnant of the once-booming zinc industry of Liège. The factory belongs to the Umicore group and produces zinc powder.