Scagliola

Outside the decorative arts field, most people are unaware of the extraordinary imitation marble known as scagliola. Within the field, its existence is known, but the technique for creating it has remained shrouded in an aura of mystery for hundreds of years.

Not surprisingly, the height of scagliola’s popularity in the United States was from the mid-1800’s to the 1930’s, when elaborately decorated churches, state capitols and theatres were being constructed. The beautiful, plaster-based material was used primarily for large columns, wall cladding, pilasters and door surrounds, in applications where large blocks of natural marble would be very expensive, if available at all. Scagliola also allowed for a nearly unlimited range of colors and patterns that were not available in natural marble. Because of the specialized, labor-intensive process required to create and restore scagliola, it too is a costly material, but it is also very durable. Some extant European scagliola dates to the 17th century, giving it an impressive record of longevity.

Creating and Restoring Scagliola

Scagliola projects require knowledge of the material and its historical use, as well as significant experience in creating it. Excellence in fabrication of the molded, gypsum plaster-based material, as well as the experienced eye of the decorative artist, are essential to achieving the finest results. Projects have included the traditional European technique that uses lumps of a doughy mixture with mineral pigment for veining, as well as the more common marezzo technique, which employs an almost liquid mixture and raw silk fiber for veining. The technique utilized is dictated by that of the original artwork.

Scagliola begins with basic recipes using gypsum plaster and mineral pigments. The mixtures for individual installations of scagliola will vary, and test batches are mixed to achieve the correct colors and properties when matching historic scagliola or marble.

Precise molds are created and the mixture is cast in the desired shape and size. Once the scagliola has hardened, the grinding and polishing process begins. Multiple hand-polishings take place over several weeks, using water and a fine grade of stone. Finally, a proprietary, surface-enhancing sealant is applied for protection. The finished scagliola is perfectly smooth, with a glossy sheen, like that of polished marble.

For scagliola restoration, an investigation is conducted initially to determine the existing conditions, probable composition and original coatings, if any. The scagliola is inspected for surface defects and photographically documented. The attachments of the scagliola to the inner supports are key to its structural integrity. When necessary, these are inspected with a fiber optic, lighted lens attached to a borescope video camera and recorder inserted through a 3/8" hole. From this information, decisions can be made regarding the entire scope of the work and the best restoration procedures to be used.

Mock-ups and/or test samples based on the investigation of the pigments are fabricated prior to the commencement of the project, demonstrating the ability to match historic scagliola. Before restoration begins, previously applied coatings are removed from the scagliola. For large patches and replacement pieces, molds are created for the mixture. The newly molded scagliola cures before the polishing takes place. The replicated artwork is approved by the client before installation.

The repair of cracked scagliola is accomplished primarily through the routing out of cracks to give them a rough, V-shape that is optimum for the adherence of the infill. The cracked and broken scagliola is patched and reinforced prior to the installation of the replicated pieces. All scagliola is properly anchored to the inner supports, and wire ties can be added for additional safety. Then, the scagliola is burnished and polished to achieve a uniform color, texture, and porosity between the original and restored areas. Repairs in the finished scagliola now have become virtually undetectable, and a non-yellowing sealer can be added for protection. Beautiful expanses of the deep, rich scagliola shine with a renewed glow that rivals its original creation.