CHAPTER VI. (XIII.)
How works in White Stucco are executed, and of the manner of preparing the Wall underneath for them, and how the work is carried out.
ยง 72. Modelled and stamped Plaster Work.
The ancients, when they wished to make vaults or panels or doors or windows or other ornaments of white stucco, were in the habit of building a skeleton of walling either of baked bricks or of tufa, that is, a stone that is soft and easy to cut. Making use of these, they built up the bones underneath, giving them the form of mouldings or figures or whatever they wished to make, cutting them out of the bricks or stones, which were afterwards put together with mortar.
Then with stucco, which in our fourth chapter (of Architecture) we described as crushed marble mixed with lime from travertine, they begin to cover the aforesaid skeleton with the first daub of rough stucco, that is coarse and granulated, to be covered over with finer when the first stucco has set and is firm, but not thoroughly dry. The reason for this is that to work the mass of the material above a damp bed makes it unite better, therefore they keep wetting the stucco at the place where the upper coating is laid on so as to render it more easy to work.
To make (enriched) mouldings or modelled leafage it is necessary to have shapes of wood carved in intaglio with those same forms that you wish to render in relief. The worker takes stucco that is not actually hard nor really soft, but in a way tenacious, and puts it on the work in the quantity needed for the detail intended to be formed. He then places over it the said hollowed mould which is powdered with marble dust, striking it with a hammer so that the blows fall equally, and this leaves the stucco imprinted; he then proceeds to clean and finish it so that the work becomes true and even. But if he desire the work to have bolder relief in projection, in the spot where this is to come he fixes iron supports or nails or other armatures of a similar kind which hold the stucco suspended in the air, and by these means the stucco sets firmly, as one sees in the ancient edifices where the stucco and the iron supports are found still preserved to the present day.[[182]] Moreover, when the artificer wishes to produce a composition in bas-relief on a flat wall, he first inserts numerous nails in the wall, here projecting less, there more, according as the figures are to be arranged, and between these he crowds in little bits of brick or tufa, in order that the ends or heads of these may hold the coarse stucco of the first rough cast, which he afterwards goes on refining delicately and patiently till it consolidates. While it is hardening he works diligently, retouching it continually with moistened paint-brushes in such a manner as may bring it to perfection, just as if it were of wax or clay. By means of this same arrangement of nails and of ironwork made on purpose, larger and smaller according to need, vaults and partition walls and old buildings are decorated with stucco, as one sees all over Italy at the present day to be the habit of many masters who have given themselves to this practice. Nor is one to suspect work so done of being perishable; on the contrary it lasts for ever, and hardens so well as time goes on, that it becomes like marble.