The Conservation of a Moisture Damaged Oil Gilded
Framed Mirror - Case Study
Bernacki & Associates, Inc.

 Abstract |    Introduction |   Discovery |   Assessment |   Treatment

Abstract

This article will review the conditions and circumstances of how to properly care for
gilded objects and furnishings. Issues regarding conservation and restoration will be
reviewed to ensure the overall integrity and safe keeping of gilded finishes.
Conservation issues will be explored to better understand how gilded surfaces can
become damaged and compromised. Issues involved in replacing sections of cast
and applied ornament, consolidation of gesso, in-filling sections of missing and
damaged gold leaf and surface cleaning will also be covered. top

Introduction

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. top

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. top

Discovery

An oil-gilded mirror measuring seventy-five inches high and seventy-eight inches wide
was stored in a wooden crate at private storage facility on the top floor of a
warehouse building. The gilded frame surrounding the mirror is of a classical revival
motif dating to the early 20th century, the mirror is silver backed quarter inch glass.
The four sides of the frame are fluted with scotia returns on the interior mirror edges
and the exterior edges are dressed flat and gilded. The four corners have square
corner blocks with rosettes inside a miter frame The mirror had been blanket wrapped
with moving pads and loosely taped along the folds. The crate was constructed out of
quarter inch plywood, fastened together by screws. The crate and mirror were staged
upright against a partition wall in close proximity to a skylight. The crated mirror,
along with several other furnishings were stored and locked for several months. top

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. Along the
lower sections on the outside face of the frame mold had begun to grow. top

Treatment

The crate along with the mirror were removed from the storage facility and brought
to Bernacki & Associate’s studio for treatment. The mirror was removed from the
crate and blanket and placed in our lab. 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
using rabbit skin glue. Because a stable and secure surface is crucial for the future
integrity of the work, the glue was injected and brushed into all open gaps,
cracks and separated seems.

After the consolidation process all areas of loss were filled with gesso.
Traditional gesso is a gypsum-based ground mixed with either a rabbit skin or
a parchment size. They type of gesso commonly used today is a mixture of calcium
carbonate and rabbit skin or hide size. While there are many types of mixtures for
gesso, for gilding it is important that the end result be finely ground, hard once cured,
able to be re-cut or carved and have clean crisp outlines. 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. Particular attention was paid to this
process, for this is the foundation in which all other materials would be applied.
If a mistake was made in the consolidation process or an in-fill was to fail, the final
result would be compromised and the entire process redone. It is important to know
the proper mixtures and rations of the materials. During this process, special
attention was taken to insure that the size was perfectly prepared so that the new
gesso will not delaminate from the existing or fail in other ways, and that the work
was kept clean throughout the entire process.

After completing the consolidation and in-filling, it was time to ready the surfaces for
gilding by the application of bole, a mixture of clay and size, specifically used in
water gliding. The type of bole used depends on the color of the clay and how this
color affects the tone of the gold leaf once applied. Finely ground pigments can be
added to the clay to ensure a color match. Bole and gesso work together to prepare
the surface for burnishing after the leaf has been laid. Burnishing is done with
a polished agate stone tool that comes in a variety of forms to work on convex,
concave or flat surfaces. The bole used in the conservation of this mirror was
a combination of red and yellow. It was brushed over the gesso fills and smoothed
with a stiff bristle brush and fine sandpaper once dry.

The gold leaf applied was a twenty-four karat French leaf supplied by Wehrung &
Billmeier Gold Leaf Company from Chicago, Illinois. Wehrung & Billmeier have been
producing gilding materials and fine gold leaf since 1905. The in-filled areas were
sized with a mixture of rabbit skin glue, deionizer water and methlayted spirits.
The exact mixture will vary depending upon surface and environmental conditions.
The leaf was laid on a cushion, cut and transferred to the surface of the frame with
a gilders tip. The leaf is applied quickly and in the same order in which the size was
applied to the in-filled areas. Once the areas were covered with leaf, the surfaces
were dabbed down with a gilders mob, a soft round brush made of squirrel hair.
Once the leaf was laid and dabbed down, the surface was gone over with a dry piece
of cotton wool (also possible to use parchment for this purpose) to ensure that no air
bubbles are trapped beneath the surface. If the surface is too wet, size will seep
through the gold and collect on the surface, leaving a residue. It’s important to wait
for the appropriate dryness before dabbing down because, if too dry and an air bubble
is trapped, the gold will pull away from the surface and leave an area of loss.
The process of applying gold leaf takes skill and experience. There are many
techniques used, each with its own application process.

After the process of applying the gold leaf, the areas were allowed to set for a period
of time and then burnished to match the existing sheen surrounding the repairs.
In areas were no new leaf was applied, as in the crazed sections of the flues and on
minor areas of loss around the rosette ornament a gilding cream, a combination of
ground gold leaf, wax and spirits was applied with a soft cotton cloth and rubbed into
or over the areas of loss to tone the damaged sections, this was an easy way to tone
small sections of loss without having to prepare and apply new gold leaf. The end
result added to an overall consistency of color and tone. Once the gilding and toning
had been competed the surfaces were covered with a micro-crystal wax for surface
protection. The wax was applied with a soft cotton cloth and rubbed over the entire
work. The end result was a completely stable and unified surface returned to its
original luster and patina.    top