42 Annual Meeting-Joint Session: Paintings and Wooden Artifacts, May 31st, "Modern Materials and Practice in Gilding Conservation", Hubert Baija

Hubert Baija, Senior Conservator of Frames and Gilding, has been responsible for overseeing the conservation of the frame collection at the Rijksmuseum Amsterdam since 1990. Numbering over 7000 frames that are now accessioned and inventoried as works of art in their own right, Baija has had the opportunity to treat frames of different styles and condition issues. During his presentation, he discussed three treatments. He emphasized the need for close study and observation of the original materials, understanding the appearance and intended effect created by the frames in their original lighting situations, and choosing reversible materials in a creative way. He noted that a treatment need not be overly involved to successfully reintegrate the gilding.
His first case study was the treatment of a Louis XVI oval frame (1777-89) that was original to the portrait it framed. The discussion addressed the past practice of covering worn gilding with bronze paint, that later had been retoned with a dark glue/pigment layer to match the discolored bronze. These layers significantly altered the intended appearance of the frame, by negating the play of dark, light, and reflectance across the complex surface. Baija demonstrated that by removing the glue and bronze paint layers (using simple solvent mixtures), only a minimal amount of inpainting was necessary to reintegrate the gilded surface. While the improvement to the frame was impressive, the appearance of the painting when displayed in the frame was also significantly improved by the intervention.
Baija’s second example demonstrated his skill as an artisan, his keen observation, and his determined investigation of a little know technique that had previously been overlooked. He stylistically identified a pair of auricular frames carved from lindenwood to c.1660-1665. Both frames had significant worm damage, had lost smaller portions of carved decoration, and were overpainted and overgilded. Only small areas of the original gilding remained intact–between 5 and 30%.
The original gilding was done using a type of mordant gilding that is not known from historical texts and has not been identified before. Using SEM-EDX imaging of cross sections, the technique was characterized: the bare wood was prepared for gilding using a thick glue layer (1 mm Th), followed by a pigmented emulsion layer, to which the gilding was applied.
Noting that the tradition of gilding in the Netherlands had been lost since the 1580s, and that more traditional (and stable) gilding techniques would not be reintroduced to the Netherlands until later in the 17th century by French Huguenots, Baija surmised that this unusual technique was in use—only in the Netherlands–for a relatively short period of time. After his initial characterization of the technique on these frames, he has since identified other examples on Dutch frames and furniture that are stylistically dated to 1650-1680. Because the technique was inherently unstable given the response of the thick glue layer to changes in humidity, many pieces gilded using this technique have subsequently been overgilded.
After cleaning the frames of non-original layers, the carved losses to the wood were reconstructed using paper mâché /methyl cellulose mixture, mixed with water. The material can be handled like clay to buildup the appropriate forms. The paper mâché shrinks slightly, allowing for application of Modostuc finishing layer. Because an isolating layer of Paraloid B-72 had been applied to the original wood surface, the paper mâché fill remains easily reversible. Shallower losses were also filled with Modostuc.
Most creative was Baija’s approach to inpainting to create the illusion of distressed gilding. Noting that the original thick glue layer would only be very slowly soluble in water, gouache was chosen to provide a brown base tone over areas of lost gilding and structural reconstruction. Islands of worn gilding were recreated using mica pigments mixed with Schminke watercolors, masterfully creating the illusion of a worn gilded surface. Final toning was done using ethanol soluble dyes in Mowilith 20. Toning could also be done using Gamblin Conservation Colors, PVA, etc. Coincidently, the dating of the frames was confirmed and the paintings and frames temporarily reunited, when an early 20thC. photograph of the frames paired with their original paintings was identified. The paintings are signed and dated 1661.
In his final example, Baija described an approach to reintegrating an area of loss in the gilding on a panel painting by Lorenzo Monaco, Stigmata of St Francis, c.1420. The area of damage was on a stepped join that was filled using Modostuc and prepared for gilding with acrylic bole from the Kolner system. Baija emphasized the importance of selecting a gold that was the correct color, but lighter in tone than the final appearance needed. He noted that any toning layers/coatings would take away from the intended appearance of the gilding—imitation of solid gold. By simply inscribing the cracks in the newly gilded loss, using horizontal lines to disrupt the vertical disruption of the loss, the gilding was effectively knocked back to the correct tone. Minor glazes to create the effect of dirt in the cracks were then applied.
Each of these treatments demonstrated issues that are common to conservation of gilded objects. Gilded surfaces are often overgilded or painted with bronze paint to recreate the impression of gold. Alternatively, gilded surfaces tend to be toned dark, either to reintegrate corroded bronze paint or to tone back gold that may seem too garish or is disrupted in other ways.
Baija’s approach is one that brings back the appreciation of frames as works of art, rather than as just accessories to paintings. It emphasizes the need to understand the original and aged appearance of the gilding, and to recover what is left of the original. His approach is one that acknowledges the frames—like objects and paintings–should be treated in reversible ways, using conservation materials distinguishable from the original materials. It thereby breaks from the traditional approach of regilding frames using traditional materials and techniques. He encourages the exploration of new materials, the use of reversible layering systems, and acknowledging the patina of time and use. An overall theme of the talk was one of reintegrating the gilding only to the level of the best-preserved area of original gilding.
For those interested in furthering their understanding of gilding and approaches to gilding restoration, Baija teaches two workshops at the Campbell Center in Mt Carroll, Illinois. “Traditional Gilding” and “Gilding Restoration” combine lecture and practical work in the studio. I attended both workshops over the last two summers, and as a result have improved my treatment approach for gilded frames. I highly recommend them.

39th Annual Meeting, ASG Morning Session, June 2nd, Student Papers, “Non-Destructive Investigation of Concealed Gilding in Architecture” by Angela Curmi, Columbia University

As an objects conservator, I tend to overlook the decorative walls of a historic house, focusing instead on the surrounding 3D aspects.  Angela’s talk really made me stop and think about the walls, as not only a significant work in themselves, but also as a record for changes in style and taste.  However the problem becomes, how do you look at certain aspects of previous wall decoration without removing the layers of historic paint?  Furthermore, how do you look at the overall motif of an entire room, without removing paint from the entire room?  Angela’s thesis from her studies at Columbia University focused on non-destructive methods of detecting gilding under layers of paint.


For her research, Angela created mock-ups of gilding motifs using gold, silver, and aluminum leaf under 3-5 layers of various paints (enough to provide visual coverage) and relied on infrared reflectography, infrared thermography, and eddy currents to see if gilding could be detected non-destructively.  The pigments of the paints can interfere with the ability to image so Angela chose historic lead white paint,  calcimite paint, and modern ‘Latex Paint’ along with burnt sienna, chromium oxide, yellow ochre, and Prussian blue [PHOTO ] on prepared wood panels [PHOTO].  For equipment Angela used a modified Kinamax nightvision webcam, modified Nikon Coolpix IR Camera, and Indigo Systems INGaAs NIR camera to test the Infrared Reflectography, as well asFLIR ThermaCAM P640 and FLIR Inframetrics InfraCAM to test the Infrared Themography [PHOTO].


Several years ago I had to attend a conference on IR imaging in an attempt to find the most practical model for my lab, so I empathized with the literature and technical data that Angela must have had to sieve through in order to find an appropriate model for her imaging.  Her results were much like I experienced, there is no ‘best’ suited for a conservator’s needs.  As Angela stated there were drawbacks to all systems, either in their range of wavelengths, ease of software use, or the quality of the image produced.   She did not find success with Thermography, mostly because of the inefficiency of heating a large space evenly to get the image.  Reflectography was more promising with the best results achieved with the Indigo INGaAs NIR camera, though its use is not necessarily practical based on cost.  The most practical model appeared to be the Kinamax model, an affordable, easily used modified web camera, the result of collaborative research from Elizabeth Nunan and Greg Smith at Buffalo State College.  For more information and purchasing of your own model go to Elizabeth’s website:  http://www.aandnartconservation.com/infraredsensitivewebcam.html