Plaster

3.4.1 Historic Alter, ST. Thomas More Chapel, Yale University. Overview of plaster and scagliola before treatment.

3.4.2 Historic Alter, ST. Thomas More Chapel, Yale University. Plaster and gilding stabilization of cracks and flaking coating.

3.4.3 Historic Alter, ST. Thomas More Chapel, Yale University. Overview of plaster and scagliola after treatment.

3.4.5 Girl Roundel, Petersen, Christian Petersen Art Museum, Iowa State University, Ames. Filling mend line during conservation treatment.

3.4.6 Girl Roundel, Petersen, Christian Petersen Art Museum, Iowa State University, Ames. Inpainting fill during conservation treatment.

3.4.7 Girl Roundel, Petersen, Christian Petersen Art Museum, Iowa State University, Ames. Overview of plaster after conservation treatment.

3.4.8 Laura & Wallace, Petersen, 1938, Christian Petersen Art Museum, Iowa State University, Ames. Overview after treatment.

3.4.9 Lincoln, Petersen, Christian Petersen Art Museum, Iowa State University, Ames. Inpainting plaster fills.

3.4.10 Pushetunequa, Christian Petersen, 1930, State Historical Society of Iowa, Des Moines. Cleaning plaster and copper alloy coating.

3.4.11 Pushetunequa, Christian Petersen, 1930, State Historical Society of Iowa, Des Moines. Mending breaks in plaster relief.

3.4.12 Pushetunequa, Christian Petersen, 1930, State Historical Society of Iowa, Des Moines. Inpainting filled losses to the sculpture.

3.4.13 Pushetunequa, Christian Petersen, 1930, State Historical Society of Iowa, Des Moines. After Treatment.

3.4.14 Rogers Studio and Plaster Groups, John, Rogers, 19th Century, New Canaan Historical Society, CT. Overview of Rogers Groups.

3.4.15 The Council of War, John, Rogers, 19th Century, New Canaan Historical Society, CT. Detail of Lincoln's head during cleaning.

Historically, plasters were mixtures of ground and burnt limestones, sands and water. Ancient Egyptians used gypsum plasters extensively for the highly decorative, painted architectural surfaces. A large deposit of gypsum (calcium sulfate, CaSO4) in Montemarte, Paris, led to the common name “Plaster of Paris”. The art of creating faux stone, or Scagliola, with a composite of plaster chips, ground gypsum and glue was used for centuries in Europe and was popular in the United States during the early 20^th century. Due to the fragility, ease of soiling of unprotected surfaces, and for aesthetics, most plaster surfaces were coated and commonly painted.

Plaster sculptures and architectural detail are typically brittle and structurally weak, often containing internal armatures of metal or wood for added support. Plaster surfaces are highly absorptive, making plaster objects susceptible to moisture exposure, including humidity. Damp conditions induce swelling of interior wood armatures and corrosion and expansion of metals that result in staining and cracking. Damp and differential expansion coefficients can lead to plaster coating loss, cracking and failure. Treatment can require cleaning, consolidation and repair of the plaster, armatures and coatings. Long term stabilization requires appropriate environmental controls that regulate humidity, temperature and light exposure.

Conserve ART provides the following services:

• Collections Assessments
• Material Analysis
• Coating Analysis
• Cleaning
• Friable Surface Consolidation
• Paint Consolidation
• Crack Injections
• Mending
• Plaster Fills
• In-Painting
• Display Consultation