PART THREE History of the Structural Conservation of Panel Paintings 188 Critical History of Panel Painting Restoration in Italy Andrea Rothe panel conservation techniques are directly related to a long history of panel construction that dates to Mantiquity and flourished from the Middle Ages to the Renaissance (see Uzielli, “Historical Overview,” herein). The ingenuity and intuition of the woodworkers of the past compensated for their lack of scientific understanding of this complex and widely diverse material. Central Italy, in particular, produced a large quantity of paintings on panel. Many of them—such as the Cimabue Crucifix in the Church of Santa Croce in Florence—were constructed to the highest standards of craftsmanship. The early woodworkers often used techniques or methods similar to those applied by modern-day restorers in treating panels—techniques such as movable crossbars (Figs. 1, 2) and coats of gesso, paint, or red lead to seal the backs of panels (Fig. 3). These sealants were probably applied as humidity barriers and protection against wood-boring insects, and panels treated in this manner have often survived better than untreated panels. The large number of panel paintings in Italian churches and muse- ums created the need for appropriate conservation work, particularly in modern times. The state-run centers of Florence and Rome have become the largest and most advanced in Italy and have generated a group of highly qualified experts in this field. The volume of panel work that has been executed in Florence far surpasses that of any other conservation center in the world. Figure 1, right Fra Angelico, Annunciation, ca. 1440. Reverse. Tempera and gold leaf on panel, 95 x 158 cm. Convent of Montecarlo, San Giovanni Valdarno. The original metal pin inserted from the front of the panel, along with the hook that latches onto it, is shown. Figure 2, far right Fra Angelico, Annunciation, reverse. This detail of the original crossbar shows the metal hook inserted into it and the metal wedge that holds it in place (see Fig. 1 for the hook- and-pin mechanism). This mechanism ensures free lateral movement of the panel. C H P P R I 189 More conservative methods have replaced the radical ones of the past. Up to the late 1950s, it was common practice in Italy to transfer onto a new support those panel paintings that had severe woodworm damage, flaking paint, or warping. Such interventions date to Napoleonic times, when many of the paintings that had been plundered from Italian churches and collections were transferred onto new supports because of severe flaking problems, caused particularly by the stress suffered during the long trip to Paris. One such example is Raphael’s Saint Cecilia (now in the Pinacoteca in Bologna), which was taken to Paris in 1798 and sub- sequently transferred from panel to canvas. Because of this drastic inter- vention and the additional effects of aging, it has adopted the surface characteristics of a canvas painting. Fortunately, as methods of wood con- servation became more effective and less radical, transfers have become nearly obsolete. Splits in the wood and failure of original joins are caused by vari- ous factors, such as rigid restraints, defects in the original construction, and excessive fluctuations of humidity and temperature. Until the dawn of synthetic adhesives such as polyvinyl acetate (PVA) emulsions and epoxies, panels were rejoined with animal glue and casein. Panels that had com- pletely separated were planed on both sides of the split to level the surface for a butt join, but this was often achieved with a considerable loss of Figure 3 original color. In other cases—such as the large panel by Fra Filippo Lippi, Riminese, Crucifixion, f ourteenth century. The Coronation of the Virgin in the Uffizi—the splits were rejoined, but no Reverse. Tempera on panel. Galleria care was taken to realign the planks, and the paint layer was simply planed Nazionale delle Marche, Urbino. Back of the down and repainted. The insertion of dovetails straddling splits was com- panel showing a gesso ground covered with a red tempera layer (possibly red lead) and an mon until the late 1950s. The V-shaped wedges, which are still used today, ornate decoration. are mentioned in a book by Secco-Suardo, although he recommends adding the dovetails as a precaution (Secco-Suardo 1866:68–70). The use of dovetails to repair split panels dates to at least the sixteenth century. They can, for instance, be made of walnut, such as in the original construction of the back of the panel for Lorenzo Lotto’s Martinengo Altarpiece in San Bartolomeo in Bergamo, dated 1516 (Brambilla Barcilon 1978:60–63). There are original dovetails found in the front of some paintings, such as Luca Signorelli’s Adoration of the Shepherds (Fig. 4). Cross-grain wedgelike Figure 4 Luca Signorelli, Adoration of the Shepherds, 1496. Oil (?) on panel, 215 ϫ 170.2 cm. National Gallery, London. Detail. The dove- tail set into the front of the panel is original. 190 Rothe Figure 5 Domenico Puligo, Virgin and Child with Saints, ca. 1522. Reverse. Oil (?) on panel, 195 ϫ 289 cm. Cathedral, Laterina, Italy. Repairs, dated 1634 on the crossbar, with applications of flax fibers and gesso over the cracks, which have also been reinforced with wedgelike insertions placed into carved-out channels. insertions are present on a panel, Domenico Puligo’s Virgin and Child with Saints, from the cathedral in Laterina, with the inscription “RESTA[urat]a 1634” on the crossbar (Fig. 5). On some occasions one finds dovetails set into the front, a method that destroys the paint layer locally, as in the organ shutters by Amico Aspertini, The Miracle of the Workman, in San Petronio in Bologna (Fig. 6). Figure 6 Amico Aspertini, The Miracle of the Workman (organ shutter), 1531. Oil or mixed technique (?) on panel, 500 ϫ 202 cm. San Petronio, Bologna. Old repairs were made with dove- tails set into the front of the panel. C H P P R I 191 Figure 7 Parri di Spinello, Madonna della misericordia, 1437. Reverse. Tempera on panel, 199 ϫ 174 cm. Museo Statale di Arte Medievale e Moderna, Arezzo. Exposed by the removal of a fake fir backing, inserts of fir with animal glue can be seen; they were inserted into lost areas of the severely worm-eaten original poplar panel. In other cases, such as the dated restoration from 1634, futile attempts were made to reinforce the splits by gluing strips of wood and hemp fibers over them. On some panel backs, however, one can find hemp fibers in very good condition that date from the time the panel was made. In two cases that were probably nineteenth-century interventions, severely worm-eaten and hollowed-out panels were filled with many different pieces of wood and abundant animal glue. These had caused extreme con- tractions and cleavage effects on the front, as on the painting by Parri di Spinello, Madonna della misericordia, from the Museo Medievale Moderno in Arezzo (Figs. 7, 8). Figure 8 Parri di Spinello, Madonna della misericordia. This close-up of the ground and paint layer shows extreme distortions caused by the contraction of the glue on the back and by the imperfect fit of the fir insets shown in Figure 7. 192 Rothe Figure 9, above In nineteenth-century Italy, as in the rest of Europe, more in- Giulio Romano, T he Birth of Bacchus, ca. 1533. depth interventions treating warpage problems became common practice. Oil on panel, 127.3 ϫ 79 cm. The J. Paul Getty The brutality with which deformed panels were straightened generates Museum, Los Angeles. Splits and surface respect for the malleable and resilient nature of wood. Panels were planed deformations, creating what is often called the fi “washboard” effect, have been caused by a down to a fraction of their original thicknesses and often humidi ed to nineteenth-century thinning of the panel and relax the warp.Then, invariably, a heavy cradle would be applied. Often application of a heavy cradle. the thinning process and application of the rigid cradle later caused severe deformations of the surface (Figs. 9, 10). Some of the methods described Figure 10, above right by Secco-Suardo include the application of hot cinders and sand, as well as Giulio Romano, The Birth of Bacchus, reverse. the addition of hot bricks, if necessary, to prolong the process. If the pan- The cradle was applied to the back when the els were severely deformed, he recommended cutting longitudinal grooves panel was thinned. Rigid and heavy, it has contributed to the splits and deformations on at intervals of 1–2 cm before applying the above-mentioned hot cinders. the front (Fig. 9). After the panel had been straightened, strips of wood were glued into the grooves (Secco-Suardo 1866:55–65). Unfortunately, cutting grooves to straighten panels is still practiced today by some restorers and accounts for the dreaded “washboard” effect. For partially deformed panels, Secco-Suardo also mentioned a method developed by a certain Déon, a Frenchman. In this method, tapered longitudinal V-shaped channels are sawn into the panel at inter- vals of 1–2 cm; V-shaped wooden strips are wedged into these with the aid of animal glue and humidity. Next the panel is placed face down on a bench and clamped tight with crossbars and wedges for an extended period (Secco-Suardo 1866:75–88). Unfortunately, all of these drastic inter- ventions can lead to the formation of a new series of cracks and splits. Today the disastrous effects of most of these radical interventions are apparent, and the general tendency is to leave distortions alone so as not to cause other problems (Stout et al.