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| Frame and gilding preservation treatments often
combine elements of conservation and restoration. The combination
of materials such as gold and other metal leaf, bole and gesso
are inherently delicate and therefore susceptible to various
environmental factors. Uneven relative humidity and temperature
can affect wood substrates and lead to expansion and contraction.
The result is often cracked and flaking gesso, bole and metal
leaf layers. Stabilizing and re-adhering unstable areas of the
surface can become an extremely time intensive process. |
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Not infrequently, frames and other gilded objects
are improperly restored with bronze paints, often applied to
mask surface abrasions and losses. The paint may have looked
acceptable upon application, but over time the metal powders
in the paint oxidize and turn dark. Fortunately, bronze paints
applied to water gilded surfaces are often easily removed with
appropriate solvents. Bronze paint applied over oil gilding is
often difficult to remove and in many cases impossible because
of the similar solubility of the paint and oil binder. |
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| Prior to the nineteenth century nearly all gilded
substrates were comprised of wood. Panels, mouldings
and carvings were all prepared by the craftsman before the
application of gesso. By the late eighteenth century; however,
the use of composition ornament, prepared by specialists and
sold to other craftsmen, permitted extensive embellishment
without the cost of carving in wood. The process involves the
fabrication of a reverse carved element, the mold, in a block
of densely grained wood. Composition, or the casting material,
was typically comprised of glue, resins and various bulking
agents. It
was pressed into the mold and removed after hardening. Ornamental
castings were (and still are) made in a variety of forms and
sizes which could then be used to enhance frame mouldings or
architectural elements such as chimney surrounds. |
| Beautiful gilded frames and furniture, with their brilliant
reflective surfaces are a result of careful preparation before
the gold leaf is applied. Gesso, a mixture of calcium carbonate
and rabbit skin glue is applied warm to the surface to be
gilded. Gesso is also frequently the ground layer applied
before other decorative surface treatments such as paint
or japanning. Gesso fills irregularities and other imperfections
in the surface of the wood resulting from carving, planing,
other tooling marks and occasionally inferior coarse wood
texture. Usually several coats of gesso are applied and allowed
to dry before the gesso surfaces are worked to create detailing
or to smooth the surface in preparation for the bole coating.
For example, sculptural details in carving are sometimes
worked in the gesso coat rather than the wood substrate. |
Further details in breast and wings of bird are carved in
the gesso layer. The restoration beak is carved pine with
a gesso coating. |
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| Bole is a mixture of clay and rabbit skin glue.
Available in several colors the bole layer can impart subtle
tonal qualities to the gold. Sometimes two or more bole
colors are applied, with each fulfilling a very specific purpose.
It is not unusual to note yellow and red bole applied to a
frame or other object. Yellow will often be applied to recesses
within and adjacent to carving; red to the elements of the
carving that stand proud of the surface. Because it is nearly
impossible to apply gold to every crevice and recess, the yellow
bole is used in these areas to create the illusion of a completely
uniform appearance. |
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| After drying, the bole is burnished; usually with horsehair
cloth. This is a critical step if the objective is to create
a continuous reflective surface. Gold cannot be burnished properly
if there are irregularities in the bole coating. |
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| Gold is usually applied in one of two ways with
either an oil size or a water/glue binder. It is not unusual
to employ both methods on the same object to create varying visual
effects. Typically, flat areas, continuous mouldings and some
times discreet sections of carving will be water gilded. |
Frames with varying colors of gold and bole. |
Whereas, recesses and most carved elements are
usually oil-gilded. Water gilding can be burnished to a high
gloss; however oil gilding is not burnished. A well prepared
and burnished water gilded surface glows like a block of bullion.
Another telltale mark of water gilding is the perfectly spaced
lap lines visible on a flat surface or continuous moulding. The
subtle effects that are possible combining water and oil gilding
are often an important part of the overall composition. |
| Gilded surfaces require very little maintenance other than
careful dusting. Longevity is best achieved by maintaining stable
environmental conditions. Because of the fragile nature of gilded
objects ongoing inspections are important. Should flaking or
curling or other defects of the gilded surfaces be noticed, it
is best to contact a conservator. Always save any surface elements
that become detached. Immediately addressing minor condition
defects will greatly reduce the cost of what otherwise can be
a very time consuming and expensive treatment. |
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©2005 Belmont Hills
Art Conservation Studios |
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