lime kiln of Ponciat

The production of lime, obtained by roasting limestone at about 900 °C , was once one of the main industries in the Meuse valley and the adjacent plateaus, where the raw material is found in abundance . Proof of this is the presence, near the surrounding villages, of the remains of ovens, the chaufours or 'tchafors' in Walloon.

We do not know the date of construction of the old lime kilns in Ponciat. They do not appear in Ferraris' (1777) or Vander Maelen's (1850) census. On the other hand, it is estimated that they would have been left in 1863 or 1864 , shortly after the death of Charles-Joseph Libion, native of Strud and undoubtedly one of the last to have worked on this site.

The structure of the furnaces, consisting of solid limestone masonry , forms the framework of boilers lined with refractory bricks . The chaufourniers, whom we called "the tchafornis," filled these kettles with straw, brushwood, and wood halfway up from the loading ports on the upper terrace (the guulards), interspersed with layers of lean coal and limestone . Then the fuel was ignited. When the flames appeared on the surface, the chaufourniers completed loading to two-thirds of the height of the boilers . It was expected that for 1T lime, after extraction of incineration waste, an average of 2T limestone and 200 kg of lean coal would be needed.

Barring accidents , the ovens burned for 8 to 10 months . They were only shut down to make major repairs . Subjected to the fire, the stones of the lower layers were transformed into small limestones that, guided by a funnel structure (the tap) , came to the outlets equipped with a system of grates. These side openings at the bottom of the tank allowed the diggers, called 'disforneus of Tireus al tchaus', to extract the lime using a saddle (a flat shovel consisting of a 3 to 4 m wooden handle and a pallet of about 15 cm. or a tool with curved teeth) before loading it into a wheelbarrow. An unloading path made it possible to unload the lime into dumpers. This work was extremely painful , if only because of the outflow of gas and smoke . Unloading was a very delicate operation and to prevent the baking mass from becoming unbalanced and collapsing, the unloader pulled the lime in small amounts from one opening to the other, so that the contents of the oven were evenly distributed on each side. dropped. While the furnace was being emptied, the boiler maker would refill the furnace from the boiler.

When it leaves the kiln, the lime is in the form of powdered granules, which is called "quicklime" or calcium oxide (CaO). This quicklime is then "slaked" by immersion in water to obtain an inert product, "slaked lime" or calcium hydroxide (Ca(OH)2), which can be used in mortars and plasters.

In particular, a coating based on slaked lime and water was applied to the walls of barns and chicken coops to repel vermin . It was also brushed onto the trunks of fruit trees to control pests. The ash from the stoves was used by farmers as fertilizer for crops.

With the advent of modern cement and fertilizers, lime lost much of its importance and, unable to compete with the big companies, most of the artisanal kilns in the region were abandoned.

These restored ovens were inaugurated in 2015.

Willem Vandenameele