What is Gesso, and How Are Gessoed Gilded Objects Cared For?
If you have a gilt framed artwork, then the frame is most likely coated with gesso under the gold leaf. What is gesso and how should gessoed frames be cared for?
Throughout history, gesso (Italian for “chalk”) has been used as the traditional ground, or preparation, for gilding frames. This thick, white, paint-like substance provides a uniformly smooth surface over wood moldings onto which gold leaf is applied. Gesso is typically made from calcium carbonate or calcium sulfate, water, rabbit-skin glue, and sometimes linseed oil. These ingredients are carefully mixed and then heated at a low temperature in a double boiler. Before the application of gesso the frame must first be coated with a primer of rabbit-skin glue to ensure optimal bonding of the gesso. Gesso is then brushed by hand over the frame’s entire wood surface. Eight to ten coats of gesso are typically required to achieve a strong, shell-like coating.
In recent times for more modern frames, gesso is sprayed from a spray booth to create a more uniform surface, which is needed on a slick, modern frame.
Above: Gesso is hand brushed onto the carved frame.
After the gesso coating has dried it is surfaced by hand using either a wet brush or linen cloth, or dry or wet sandpaper.
The frame’s carved details can be lost when gesso is applied, so it is often necessary to carve back the gesso layer with small tools to redefine or augment the ornamentation. This technique is known as recutting or tooling. Perfected by the French, recutting was used on frames with finely carved surfaces dating to the 18th century and earlier. Sometimes early frame makers also added decoration to the gesso, which often took the form of cross-hatching or punchwork. Another ornamentation technique that incorporates gesso is pastiglia, which was especially popular during the Italian Renaissance, when frame makers applied liquid gesso in layers to create low-relief decoration. Conservators and frame makers still practice today all of these techniques, both in restoring period frames and in creating new frames.
Gesso is highly sensitive to changes in climate and can shrink, flake, or crack if exposed to cycles of excessive heat, cold, humidity, or dryness. Follow these guidelines for proper care of your gilt frames:
Store your gilt framed artwork in a stable environment with as few fluctuations in relative humidity and temperature as possible. Avoid storing gilded frames in places like a damp basement or hot attic.
Check antique gilded surfaces regularly for cupping or cracking on the surface.
When it comes to cleaning an antique gilded frame, never use a moist cloth. Even gentle use of a soft dry cloth can cause damage to fragile surfaces. Avoid do-it-yourself cleaning methods. When it is time to clean your gilt framed art always bring it to a conservator for professional cleaning.
Damage to the gesso layer can also occur when moving a frame. Seek professional assistance from fine art service providers who have the skills and experience to safely pack, crate, transport, and install diverse artworks.
It is worth noting that artists, too, have long used gesso as a primer for paintings. This gesso, however, is not the same as that used for gilding frames: it contains less glue to facilitate adhesion of the paint and to allow for more flexibility when applied to a canvas support. The use of gesso in paintings dates as far back as ancient Egypt and became common in Medieval and Renaissance panel paintings. In the 20th century artists began to use acrylic gesso—versus the traditional, rabbit-skin glue composition that is still used for gilding—because its ingredients allow for even greater flexibility on canvases and other non-wood surfaces, making them less susceptible to cracking.
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Above: Gesso is applied in a spray booth onto a modern frame.