Proportionate Enlargement
[§ 48, Transference of the full-sized Model to the Marble Block, ante, p. 151.]
‘To enlarge the figure proportionately in the marble.’ Vasari has said, ante, p. 150, that the model is to be the full size of the marble so that there would be no question of enlargement but only of accurately copying the form of the model in the new material. For this mechanical aids are invoked, the latest and most elaborate of which is the ‘pointing machine’ now in common use. The appliances in Vasari’s time were much simpler. Cellini, in his Trattato sopra la Scultura, describes the mechanical arrangements he made for enlarging a model to the size of a proposed colossal effigy, and the principle is the same whether there is to be enlargement or exact reproduction.
The model, and a block roughly trimmed by rule of thumb to the size and shape required, but of course somewhat larger than will ultimately be needed, are placed side by side on tables of exactly the same form and dimensions. About the model is set up a sort of framework simple or elaborate, according to the character of the piece, and a framework precisely similar in all respects is disposed about the block. A measurement is then taken from one or more points on the framework to a point on the model, and from a point or points similarly situated on the other framework, and in the same relative direction, a similar measurement is led towards the block. As this is ex hypothesi a little larger than the model, the full measurement cannot be taken until some of the superfluous marble has been removed by suitable tools. When this is done a point can be established on the block exactly corresponding to the point already fixed on the model. This process can be repeated as often as is necessary until all the important or salient points on the model have been successively established on the marble block, which will ultimately have approached so nearly to the exact similitude of the model, that the artist can finish it by the eye.
The nature of what has been termed the framework, from which all the measurements are taken, may vary. Cellini, on the occasion referred to, surrounded his model with a sort of skeleton of a cubical box, from the sides and corners of which he measured. In the Encyclopédie of Diderot and d’Alembert, of the middle of the eighteenth century, similar square frames, like those used as stretchers for canvases, are suspended horizontally over model and block, and plumb lines are hung from the corners, so that skeleton cubes are established, which would answer the same purpose as Cellini’s box. See Plate X, A. The arrangement contemplated by Vasari was somewhat simpler. He does not establish a complete hollow cube about his model and his block, but is apparently satisfied with erecting perpendiculars beside each, from which the measures would be led. The carpenter’s square (squadra) he has in mind consists of two straight legs joined together at right angles. If one leg be laid horizontally along the table the one at right angles to it will be vertical, and from this the measurements are taken. In the treatise on Sculpture by Leon Battista Alberti there is an elaborate description of a device he invented for the purpose in view, and one of his editors has illustrated this by a drawing reproduced here in Plate X, B. The device explains itself, and any number of similar contrivances could be employed.