The Ten Books on Architecture, 2.4.3

Vitruvius  Parallel editions

‹‹‹ Vitr. 2.4.2 | Table of Contents | Vitr. 2.5.1 ›››

Gwilt translation

3but plaster readily adheres to and dries on walls built with new pit sand, and vaulting may safely spring from them. If sand have been dug a long time, and exposed to the sun, the moon, and the rain, it loses its binding quality, and becomes earthy; neither when used does it bind the rubble stones together so as to prevent them sliding on their beds and falling out: nor is it fit to be used in walls where great weights are to be supported. Though pit sand is excellent for mortar, it is unfit for plastering; for being of a rich quality, when added to the lime and straw, its great strength does not suffer it to dry without cracks. The poorness of the river sand, when tempered with beaters, makes the plastering as hard as cement.

Morgan translation

3But pitsand used in masonry dries quickly, the stucco coating is permanent, and the walls can support vaultings. I am speaking of sand fresh from the sandpits. For if it lies unused too long after being taken out, it is disintegrated by exposure to sun, moon, or hoar frost, and becomes earthy. So when mixed in masonry, it has no binding power on the rubble, which consequently settles and down comes the load which the walls can no longer support. Fresh pitsand, however, in spite of all its excellence in concrete structures, is not equally useful in stucco, the richness of which, when the lime and straw are mixed with such sand, will cause it to crack as it dries on account of the great strength of the mixture. But river sand, though useless in “signinum” on account of its thinness, becomes perfectly solid in stucco when thoroughly worked by means of polishing instruments.