Schedule C.1.2. A code of professional practice for the conservation of the façade of ordinary buildings in the historical towns. The experience of Ortygia

Typology of the intervention	C Preparation of the masonries C.1 Defence salty migrations C.1.2 Temporary plaster
Purpose of the work	The masonry shows the plaster very deteriorated or absent, marked, in one or more parts; deterioration due: to the located loss of plants; to the rising damp; to the absence of a suitable protection to the summit of the masonries. Under these conditions the masonry has been shown saturated of soluble salts. It needs, before providing to any intervention, to extract soluble salts.
Formality of the intervention	Before effecting the laying of the temporary plasters is necessary to perform: interventions on structures; generic work of preparation of the masonry for the following laying of plasters; the accurate cleaning of the masonry with water and sorghum brushes. In the so prepared masonry is spread a layer of plaster, with limited thickness, manufacturing a generic mortar. After an enough period to allow the setting of the mortar (varying in relation to the environmental conditions) the temporary plaster is eliminated and, only in the parts that are more polluted, the treatment is repeated. In the zones where the phenomenon of the salty migration had to occurred again, it should better act to a further extraction through "clay packs" (C.1.3).
Specifications on the materials	The temporariness of the intervention doesn't require a detail care in the preparation of the plaster, that can be constituted by a layer, of limited thickness, obtainable with a ordinary lime mortar. The medium/coarse- grained aggregates, deprived of dusts, of salts and of other polluting substances, must be clean.
Warning	Between the mortar and the wall (made damp from the cleaning and from the ordinary mortar on this applied) an osmotic phenomenon occurs; in presence of two different salty concentration solutions (the wall and the mortar) the transfer of salts is activated in direction of the small concentration solution (the temporary plaster). In the extreme case of a ordinary mortar (because of a polluted aggregate) with a salty concentration greater than that present in the masonry, stretching the plaster, exists the risk to introduce salts rather than to extract them.

Summarizing files for a critical reflection on the effects of the workmanships

C.1.2 - elements of judgment
Effects	Description
action	salts' extraction
control of action	impossible
check of action	possible
time of intervention	long
collateral effects	absent
Elements of analysis	Description
maintenance of informative content	not remarkable
potential reversibility	reversible
compatibility with the support	good
easy application	good
possibility of maintenance	non remarkable
duration of the effects	immediate effect
cost	low

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