The subsurface drawing
Subsurface drawings are sometimes visible to the naked eye, particularly on thin-material or unfinished paintings. The current detection and documentation of many drawings has now become possible through the use of the infrared technique, in particular of infrared reflectography which, as mentioned, was developed for application on paintings by J. R. J. van Asperen de Boer in the early 1970s.The most substantial body of published information on subsurface drawings is associated with paintings from the Renaissance period . This is because the drawing on the primitive painted panels is more easily detected due to the painting technique: commonly a carbon black drawing on a light gypsum and glue preparation, covered with fine layers of paint (figs. 54-55).
The preliminary sketch
From the 16th Century certain artists began to use a gray under-modelling that obscured the underlying design, the paint layers became more opaque and the color of the preparation began to change . The purpose and function of the subsurface drawing also changed considerably with the introduction of the independent oil sketch , which, having originated in Venice after the mid-Sixteenth Century, became common in the Seventeenth Century. In fact, subsurface drawings have not been found either on paintings by Seventeenth-Century artists, such as Rubens, van Dyck, Caravaggio or Jan van Goyen, nor in Eighteenth-Century ones such as Wattau, nor in Nineteenth-Century works such as those of Ingres . It is presumed that many artists made some kind of preliminary sketch on their canvases even if their detection with current techniques is not always possible and therefore further investigations would be necessary.
The transfer of the drawing
As regards the realization of the preparatory drawing, today we know that in many cases this was done separately in order to be transferred once completed on the support before receiving the paint.
Inestimable heritage of the ancient bottegas (workshops), the drawings accumulated over time or made specifically for a new painting had in any case to be transferred on the support intended for painting, using tracing and enlargement methods so as not to allow errors. This therefore also made it possible to avoid retracing the creative process and consequently guaranteeing fidelity to the master’s model, especially in the case in which the work of aids was used.
Pouncing is another of the most ancient techniques that served to bring back, without variations in scale, a drawing made on paper on a new support. The design was heavily pierced along each single contour with an “agugella”, that is a metal rod with a tip similar to that of a needle.
Placing the perforated sheet on the new support, the holes were beaten with a wide-weave cloth bag containing carbon dust, so that the position of each single hole was imprinted on the support. The drawing could then easily be retraced and strengthened with ink applied with a brush (figs. 56-57). The traces left by the dust were then eliminated by dusting the surface with a bunch of feathers.
Obviously the procedure involved the loss of the model, soiled by coal. This inconvenience could be solved by placing a double sheet of paper when the lines were punctured, in order to obtain a duplicate and keep the original for further use.
Retracing, moreover, has been one of the most popular techniques for transferring a drawing to a new support without any variations in scale. Already used in the Thirteenth-Fourteenth Century workshops, the system is well attested throughout the Renaissance, with methods similar to those that today regulate the use of carbon paper. The technique involved blackening the side of the sheet on which the drawing to be transferred was made more or less homogeneously with coal dust. Then the drawing was placed on the new support and eventually fixed temporarily to prevent it from moving during the operation. At this point, very simply, the contours of the design were traced with a stylus, so that a dark trace could be deposited on the new support in correspondence with the pressure lines. After having traced the engravings delimiting the gilding and the main architectural elements as usual, the painter went over the drawing in charcoal with ink applied with a brush with aqueous binder, or with carbon black in egg tempera.
In the event that the transfer of a drawing were to be accompanied by a change of scale, the painter resorted to squaring the original, in order to break down the composition into single regular portions more easily reproducible.
Having squared the support on a scale higher or lower than the model, the individual portions were then carried over, having specific references or only purely indicative ones according to the width of the determined grid. If, on the other hand, for some reason the original was not to be dirtied with the squaring, a frame with a grid made up of cords could be superimposed on the image.
The deep layers of painting
Equally important for the study of the creative path is the investigation of the deep layers of painting, that is, the layers richer in coloring material. Their examination makes use primarily of X-ray radiographic techniques and stratigraphic analyzes carried out on samples taken from the works in question.
Thanks to the radiographic examination, as the radiologist Ludovico Mucchi acutely points out, the painting is almost divided into two distinct parts: “a deep layer, rich in coloring material” which is the most clearly detectable by X-rays and “a superficial layer, consisting of poorly colored brushstrokes that do not give visible signs or give little evident ones “. The radiographic examination allows us to identify the deepest pictorial part, always painted with clear and confident lines as the most spontaneous and personal part of the process, “the painter has no hesitation or restraints and in making the painting his hand follows a specific and constant creative rhythm: gestures that become a stroke and the stroke that becomes painting “. In the finishing work of the painting, on the other hand, the painter changes his brushstroke more or less consciously conditioned “by the uses of his time by the pictorial current dictated by this or that master and finally also by the will of the client (…), all these considerations explain the large number of paintings made by different hands which, while stylistically similar on the surface, diverge in the deep structure, the one highlighted by the X-ray examination.
But there is also another aspect that underlines the importance of the radiographic characteristics of the deep layer: while the pictorial surface is the one that undergoes the greatest wear over time, and is therefore the one most tampered with by restorers, the deep layer, more protected and consistent, is much more resistant to the insults of time. If the criterion is accepted that the painting, due to wear and tear, remains a film so small as to leave only some radiographic traces, it must be admitted that the multiple restoration interventions can also considerably betray the original work” .
Si veda a proposito: H. W. Van Os, M. Prakken, The florentine Paintings in Holland: 1300-1500, Maarseen, 1974; AA.VV., The Scientific Examination of Early Netherlandsh Paintings: Application to Art History, “Nederlands Kunsthistorisch Jaarboek”, vol. 26, 1975; M. Faries, Underdrawings in the workshop productions of Jan van Scorel. A study with infrared reflectography, “Nederlands Kunsthistorisch Jaarboek”, vol 26, 1975, pp. 89-228; J. R. J. Van Asperen de Boer, An introduction to the scientific examination of painting, “Nederlands Kunsthistorisch Jaarboek”, vol. 26, 1975, pp. 1-40; AA.VV. The early Venetian paintings in Holland. Catalogue of the Exhibition (Florence, 1978), a cura di H. W. van Os, J.R. J. van Asperen de Boer, Maarssen: Gary Schwartz 1978; J. P. Filedt Kok, Underdrawing and other technical aspect in the paintings of Lucas van Leyden, “Nederlands Kunsthistorisch Jaarboek”, vol. 29 1978, pp. 1-184; J. R. J. Van Asperen de Boer, A Scientific Re-examinatio of the Ghent Altarpiece, Oud Holland, 93, 1979, pp. 141-214; A. Smith e M. Wyld, Altdorfer’s Christ taking Leave of His Mother’, “National Gallery Technical Bulletin”, vol. 7, 1983, pp. 50-64; C. Bertelli, A. Gallone, M. Milazzo, M. Olivari, Il disegno nascosto dello Sposalizio, in Raffaello giovane e Città di Castello, Catalogo della mostra (Città di Castello, 1983-1984), Città di Castello, 1983, pp. 95-118; H. W. van Os, J. R. J. van Asperen de Boer (a cura di), La pittura nel XIV e XV secolo. Il contributo dell’analisi tecnica alla storia dell’arte, Comité International d’Histoire de l’Art, Atti del XXIV Congresso Internazionale di Storia dell’Arte (Bologna, 10-18 settembre 1979), Bologna, Clueb 1983; AA.VV., Indagine su Raffaello, in Raffaello a Firenze, Dipinti e disegni delle collezioni fiorentine, Electa 1984, pp. 239-68; M. Chiarini, La Madonna del Granduca: deduzioni tecniche e stilistiche dopo le recenti indagini scientifiche, in Raffaello: Recenti Indagini Scientifiche, a cura di O. Curti, A. Gallone Galassi, Atti del simposio (Milano, 1986), Milano, ICOM – Comitato Nazionale Italiano 1986, pp. 21-29; D. Bertani, E. Buzzegoli, M. Cetica, L. Giorgi, D. Kunzelman, P. Poggi, Andrea del Sarto in riflettografia, in Andrea del Sarto 1486-1530. Dipinti e disegni a Firenze. Catalogo della mostra (Firenze, 1986-1987), Milano, D’Angeli-Haeusler Editore 1986, pp. 341-357; E. Buzzegoli, D. Kunzelman, La nascita di Venere in riflettografia IR, in La Nascita di Venere e l’Annunciazione del Botticelli restaurate, Catalogo della mostra (Firenze 1987), “Gli Uffizi. Studi e Ricerche”, 4, Firenze, Centro Di 1987, pp. 63-71; E. Buzzegoli, D. Kunzelman, L’Annunciazione in riflettografia IR, in La Nascita di Venere e l’Annunciazione del Botticelli restaurate, Catalogo della mostra (Firenze 1987), “Gli Uffizi. Studi e Ricerche” Firenze, Centro Di 1987, pp. 72-73; J. Dunkerton, A. Roy, A. Smith, The Unmasking of Tura’s Allegorical Figure, “National Gallery Technical Bulletin”, vol. 11 1987, pp. 5-35; M. Laurenzi Tabasso, Le indagini scientifiche, in La Pala Ricostruita. L’incoronazione della Vergine e la cimasa vaticana di Giovanni Bellini. Indagini e restauri, Catalogo della mostra, a cura di M. R. Valazzi, (Pesaro, 1988), Venezia, Marsilo 1988, pp. 127-143; A. Aldrovandi, Le indagini diagnostiche, in AA.VV., Fra Bartolomeo la Pietà di Pitti restaurata, Firenze, Centro Di 1988, pp. 57-64; D. Scrase, Cosimo Tura, The Crucifixion with the Virgin and St John, The Hamilton Kerr Institute, vol. 1, 1988, pp. 69-71; AA.VV. La tecnica pittorica del Botticelli: un’analisi comparata, in L’Incoronazione della Vergine del Botticelli: restauro e ricerche, Catalogo della mostra (Firenze, 1990), a cura di M. Ciatti, Firenze, Edifir Edizioni 1990, pp. 85-108; L. L. Rissotto, Tecnica e metodo di esecuzione pittorica, in La Danae e la pioggia d’oro. Un capolavoro di Antonio Allegri detto il Correggio restaurato, a cura di M. G. Bernardini, Roma, Multigrafica Editrice 1991, pp. 41-44; M. Ciatti, A. Tortorelli, Il dipinto: tecnica pittorica e restauro, in Raffaello a Pitti. ‘La Madonna del baldacchino’ storia e restauro, a cura di M. Chiarini, M. Ciatti, S. Padovani, Catalogo della mostra (Firenze, 1991), Firenze: Centro Di 1991, pp. 79-82; P. Spezzani, Le riflettografie, in Il polittico Averoldi, a cura di E. Ragni Lucchesi, G. Agosti, Catalogo della mostra (Brescia, 1991), Brescia, Grafo edizioni 1991, pp. 169-171; P. Spezzani, Le radiografie e le riflettografie, in AA.VV. Carpaccio, Bellini, Tura, Antonello e altri restauri quattrocenteschi della Pinacoteca del Museo Correr, a cura di A. Dorigato, Catalogo della mostra (Venezia, 1993), Milano, Electa 1993, pp. 216-217; A. Massing, N. Christie, The pseudo-Bramantino’s Deposition of Christ, The Hamilton Kerr Institute, vol. 2, 1994, pp. 50-60; Paolo Spezzani, Breve nota sulle riflettoscopie in infrarosso della Pala di San Giobbe di Giovanni Bellini, in Quaderni della Soprintendenza ai Beni Artistici e Storici di Venezia,1994, pp. 27-28; J. Wadum, Vermeer illuminated: conservation, restoration, and research. A report on the restoration of the View of Delf and The girl with a pearl earring by Johannes Vermeer, Mauritshuis, Wormer, The Hague 1994; A. Aldrovandi, O. Ciappi, Indagini radiografiche e riflettografiche a confronto, 1510-1515. “Concerto”, Firenze, Galleria Palatina di Palazzo Pitti, in Tiziano. Amor Sacro e Amor Profano, Catalogo della mostra (Roma, 1995), Electa 1995, pp. 361-362; AA.VV., La tecnica di Fra’ Bartolomeo: studi e ricerche, L’età di Savonarola, in Fra Bartolomeo e la Scuola di San Marco, Catalogo della mostra (Firenze, 1996) a cura di S. Padovani, Firenze, Venezia, Marsilio 1996, pp. 293-313; F. Falletti, Il restauro della Madonna di Piazza: nuove immagini per un vecchio problema, in I Medici, il Verrocchio e Pistoia. Storia e restauro di due capolavori nella Cattedrale di San Zeno, a cura F. Falletti, Livorno, Sillabe 1996, pp. 75-83; M. E. Avagnina, La tecnica pittorica di Pisanello attraverso le fonti e l’analisi delle opere veronesi, in Pisanello, Catalogo della mostra (Verona, 1996) a cura di P. Marini, Milano, Electa 1996, pp. 465-476; B. Casavecchia, La tecnica di Carlo Crivelli, in “Kermes”, X, n. 30, Nardini 1997, pp. 12-20; AA.VV., Il colore ritrovato, Bellini a Venezia, a cura di R. Goffen e G. Nepi Scirè, Milano, Electa 2000
AA.VV., Preparazione e finitura delle opere pittoriche, a cura di C. Maltese, Mursia 1993
Nelle opere di particolare complessità il riporto del disegno preparatorio sul supporto definitivo poteva infatti essere ulteriormente mediato dalla realizzazione del bozzetto, un dipinto di dimensioni inferiori a quelle che si dovevano ottenere, che serviva a valutare in maniera sintetica la composizione e l’uso del colore.
Citazione tratta dallo studio di L. Mucchi, A Bertuzzi, Nella profondità dei dipinti, La radiografia nell’indagine pittorica, Milano, Electa 1983, p.163.