Earthen mortars in Cremona:characterization and firs hypothesis of dating

The buildings of the Middle Age or of the Modern Era in Cremona, even if they show a great complexity are characterized by the almost exclusive use of clay mortars , often also for the plasters, and even for the brick vaults, until the second half of the nineteenth century. There are other similar cases in Lombardy, but here it is clear that it is not a poor substitute of the lime mortar, but a conscious choice: lime, especially in peacetime, was easily available. The estimates and descriptions - especially in nineteenth-century , when they became more thorough, showing respect to the lime mortar a very negligible saving, since this clay - plastic, as to the sources said - requires a long and accurate handling. The confirmations of the hypothesis of the rare but attentive recent literature (Bonazzi Fieni, 1995, Fieni 1998). The availability of additional samples within the stratigraphic units of which it is possible to set an absolute dating and a better understanding of the processes suggest additional analytical tests on clay minerals present: the questions are numerous, e.g. the presence of lime and its function, the origin and role of the sands, the subsequent supply points near the town, the possible difference from bricks clay. It is necessary to determine whether the variation of time or the type of position corresponds to vary the specific characteristics of the mortar. The frost blocks the building site that uses lime mortars, the clay would allow more time. The properties of certain clay minerals to adsorb water may be useful in many respects in a climate where the relative humidity is high. The empirical knowledge would allow the exploitation of a country resource. Also in analytical methodologies to answer these questions also require special attention.