Often furnishings, works of art, and decorative objects must be packed away and placed in storage. Much care must be taken in the proper handling, preparation, transportation and environment in which these valuable items will reside. The consideration of structural stability, surface fragility, and environmental parameters are key issues in the preservation of an object’s integrity. A basic understanding of an object’s construction materials and how these materials react to changes in climate, moisture, and time in storage is the first step in ensuring the preservation of a work of art.

Issues regarding surface protections and a stable environment are most important when dealing with gilded objects and furnishings. There are two basic techniques of gilding onto a wooden substrate. The first is water gilding, which uses collagen glue and oil gilding, where the gold leaf is adhered to the ground by an oil- based size. Water gilding is laid onto a porous ground, like a gesso surface, which allows the glue to penetrate into the substrate and bind not only to the gold leaf but also the ground itself. The second basic gilding technique is oil gliding which is applied to a solid substrate such as bronze, stone or wood. Traditionally oil gilding is used on outdoor sculptures and architectural details while water gilding is used on frames, furnishing and other interior decorative details. Water gilding can be burnished to a highly reflective shine, while oil gilding cannot. Each process has its own application methods and materials, as well as aesthetic capabilities. These two different types of gilding finishes impinge on the inherent nature of the materials and the matrix of how these materials work together and are affected by outside circumstances.

Discovery

An oil-gilded mirror measuring seventy-five inches high and seventy-eight inches wide was stored and locked for several months at private storage facility on the top floor of a warehouse building. The mirror had been blanket wrapped with moving pads loosely taped along the folds, and placed in a plywood crate fastened together by screws. The crate and mirror were staged upright against a partition wall in close proximity to a skylight.

Assessment

The owner of the gilded mirror discovered that water had been leaking from the skylight onto the crate and many of the other items in the storage facility. Upon assessment there was immediate evidence that water had saturated much of the outside surfaces of the crate. The crate was water stained on the front and top edge and the plywood in these areas was warped and delaminating. The crate was opened for further investigation of the integrity of the mirror inside. Water had migrated through the frame of the crate and saturated the blanket, exposing the mirror to moisture. Sections of the gold leaf had begun to lift from the wooden substrate of the mirror along the frame and relief portions of the ornament at the corner medallions. The most severe damage to the mirror was along the lower front section of the frame and the four corners with applied relief ornament. In addition,
several areas of loss were scattered throughout the surface and sections of gesso had been exposed and damaged. The moisture had caused the natural hide skin glue used to apply the gold leaf to fail. Not only had large portions of gesso and gold leaf become detached, several areas of gilding along the fluted sections had begun to craze and lift due to compromised adhesion from moisture exposure and
environmental instability. It was also evident that the fibers of the blanket had caught sections of the rosette corner blocks and been pulled away from the substrate. Small pieces of ornament, gesso and gilding were entangled in the blanket or lay at the bottom of the crate. Minor abrasions were  scattered across the glass. Mold had begun to grow along the lower sections on the outside face of the frame.

Treatment

All detached sections of ornament were collected from the crate and blanket and mapped out as to their original location on the mirror.

The biological growth on the surfaces of the frame were treated, and the entire mirror was then cleaned of dust, debris and surface residues to allow for conservators to specify the type of gold leaf to apply and the tone of bole needed for matching the new areas to the existing tone and color of the original finish. Once the materials had been specified, all loose and lifting sections of gesso and leaf were consolidated. Areas of loss were rebuilt to meet the existing profiles and sections of ornament that had missing details were either re-cast or built up with gesso and carved back to blend with the original compositions. Given the large amount of surface area and the severity of the damage, this process took several days to complete.

The gold leaf applied was a twenty-four karat French leaf. Once the gilding had been competed the surface was covered with a micro-crystal wax for protection. The restored mirror was secured in the custom built crate.