Hard Water Scale and Incrustations

Rain and groundwater naturally dissolve atmospheric carbon dioxide and, while doing so, they turn into aqueous solutions of carbonic acid, a weak acid  

In the ground and when in contact with rocks, the acid solution reacts with limestone, and the result is a solution of calcium bicarbonate  

If the water then evaporates, the dry calcium bicarbonate decomposes, recreating calcium carbonate, which precipitates and forms hard deposits and incrustations while carbon dioxide and water are released into the atmosphere  

Efflorescence, The solvent properties of water also causes efflorescence, a phenomenon whereby soluble or slightly soluble substances migrate from the interior of porous solids to the surface, where they precipitate. Efflorescence is an important factor in the decay and disintegration of many rocks, and of human-made porous materials such as ceramics, and even of some types of glass. On archaeological objects, efflorescence generally occurs mostly as a white, powdery, but somehmes consolidated accretion on the surface of the objects. Calcite, a form of calcium carbonate, is one of the most common substances to effloresce on archaeological ceramics. 

Efflorescence usually takes place when groundwater penetrates within porous solids, where it leaches (dissolves) soluble salts from the solids. When the water with the leached solids eventually evaporates, the soluhon migrates toward the surface if the water continues to evaporate, the dissolved salts are redeposited, forming small crystals just below and on the surface of the objects. The forces generated by the crystallization of the efflorescent salts below the surface (in the bulk of the solid), as well as 

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