Fresco - The Aggregates

Inert aggregates are added to the lime putty to give the mortar strength and stability. Lime putty by itself would shrink too much and would crack. Sand, marble dust, or particles of crushed brick or unglazed tile can serve as aggregates, slightly coarser materials being used in the lower coats of mortar and the finer aggregates in the top layers. The sand should be sharp, free of clay, loam, gypsum, or mica. Aggregate materials should settle to the bottom of a jar of water without leaving the water cloudy. If they are not clean, they must be washed on a screen with a hose and spread out again to dry. They should be stored in clean burlap sacks for if they are piled on the ground, they may pick up impurities which might later cause efflorescence. Marble dust or marble meal, if obtained from a sculptor, should be checked with a magnet for particles of tool steel which could rust in the fresco. The sand or other aggregate must be dry when it is combined with the lime putty since a coating of water on a grain of sand would prevent the lime from sticking closely to it.

[Kay, Reed. The Painters Guide to Studio Methods and Materials. Englewood Cliffs, NJ: Prentice-Hall, Inc., 1983. p. 174]

NOTEBOOK | Links

Copyright

The contents of this site, including all images and text, are for personal, educational, non-commercial use only. The contents of this site may not be reproduced in any form without proper reference to Text, Author, Publisher, and Date of Publication [and page #s when suitable].