Results of study of collection of 300 samples of plasters and mortars verified that micropetrographic analysis of sandy fraction of mortars and plasters, together with the assessment of the stage of matrix re-crystallization, can in almost 95% cases confirm or exclude the assumed age of the particular construction phases.

Mixture ratio of lime and sand recommended by Šujanová (1981) for identification of Romanesque, Gothic and Renaissance mortars and plasters was not verified.

The research has been supported by Czech Grant Agency projects No.: 103/99/0941 and 103/00/0607.