At the UNESCO Convention held between 22 and 29 November in Bali (Indonesia), it will be decided to declare the candidacy of the Lime of Morón as Intangible Cultural Heritage of Humanity. The candidacy is presented by the Spanish Historical Heritage Council under the title "Revitalization of the traditional knowledge of artisanal lime in Morón de la Frontera, Seville, Spain", on the initiative of the Cultural Association Hornos de Cal de Morón, with the endorsement of the Ministry of Culture of the Andalusian Regional Government and the Spanish Ministry of Culture and with the support of artisanal and cultural associative sectors.
The reaction
The reaction that takes place in the limestone firing process is as follows:
C03Ca (Calcium carbonate) + Heat (1000ºC) = CaO (Quicklime) + CO2 (carbon dioxide gas)
Quicklime is not used directly in construction, but is combined with water in an exothermic reaction to produce calcium hydroxide (slaked lime), a generally white product, which may be in powder or paste form if it contains an excess of water. The chemical reaction is as follows:
CaO (quicklime) + H20 (water) = Ca (OH) (slaked lime) + Heat
Slaked lime has been used since time immemorial to paint wall surfaces, in what we call whitewashing and also mixed with different types of aggregates in the preparation of mortars.
The slaked lime, either as paint or as mortar, in contact with the carbon dioxide in the atmosphere turns back into hard stone, exactly like the stone that was originally taken from the quarry. According to the following process it becomes stone again:
Ca (OH) (Slaked lime) + CO2 (carbon dioxide gas) = CO3Ca (calcium carbonate) + H2O (water)
The process starts with calcium carbonate C03Ca and ends in an architectural element of calcium carbonate CO3Ca manipulated in terms of colour, shapes and textures by the creative imagination of man.
