FTIR surface analysis for conservation

Abstract

Several FTIR techniques are surface-sensitive. This sensitivity can be utilized to help with a wide range conservation issues. Examples from object degradation studies, conservation materials performance assessment and monitoring are presented. These are used to discuss the issues, advantages and information that can be drawn from studies. Glass degradation was quantified on the surfaces of cover glasses from important Nineteenth century daguerreotypes using Germanium attenuated total reflectance. The very limited information depth endowed by the high refractive index crystal gave good sensitivity when other techniques such as sectioning and scanning electron microscopy had failed to detect a gel layer present. The inner glass surface was always more deteriorated and the degree of deterioration inversely correlated with the distance between the inner glass surface and the daguerreotype or brass matt surface. Reflection-absorption FTIR microscopy has been combined with an excimer laser to determine the water content of a series of sections through the depth of a wax. A common wax used to protect metals has been found to take up liquid water in humid environments and hold that water close to or at the metal surface. An adjustable height gold mirror was used to bounce the IR beam many times across a surface, which can give extreme sensitivity. Haze and smoke generators are increasingly being introduced into displays or for special events or filming. Very low detection limits (1 ng) were found using gold coated glass slides to detect haze deposits.

The Samuel F. B. Morse statue in Central Park: scientific study and laser cleaning of a 19th-century American outdoor bronze monument

“…Acrylic lacquers are coupled with a sacrificial wax topcoat that is renewed yearly in the case of Morse. Since 2003, two types of cyclically renewable wax topcoats have been used by CPC's conservators: (1) Boston Polish ™ , also known as "butchers" paste wax, a carnauba-based wax, in use from 2003 to 2006; (2) Renaissance microcrystalline wax ™ , a mixture of Cosmoloid H80 and BASF A wax [22,23], used from 2007 to In terms of coloring, verbal accounts and visual observation suggested that the Morse sculpture might have been coated with pitch at some early stage, although there are no written records of this intervention. The color of organic coatings in bronze sculptures is also sometimes obtained through the addition of bitumen, which might lend the coating a dark or brown hue [24].…”

“…It seems plausible that the water enriched with these ions could become aerosolized by the constant traffic whisking by and deposited onto the bronze. Thickett and coauthors [22,23] have demonstrated that water may be retained at the interface between the superficial layer of Renaissance wax and the coating underneath, further enhancing the corrosive attack. On ferrous metals, like steel, the prolonged exposure to this trapped moisture after the protective period of the coating might increase the rate of corrosion.…”

The Samuel F. B. Morse Statue in Central Park: Scientific Study and Laser Cleaning of a 19th-Century American Outdoor Bronze Monument

“…Acrylic lacquers are coupled with a sacrificial wax topcoat that is renewed yearly in the case of Morse. Since 2003, two types of cyclically renewable wax topcoats have been used by CPC's conservators: 1) Boston Polish™, also known as "butchers" paste wax, a carnauba-based wax, in use from 2003 to 2006; 2) Renaissance microcrystalline wax™, a mixture of Cosmoloid H80 and BASF A wax [22][23], used from 2007 to date for protecting outdoor bronze sculptures in Central Park.…”

The Samuel F. B. Morse Statue in Central Park: Scientific Study and Laser Cleaning of a 19th-Century American Outdoor Bronze Monument

“…Acrylic lacquers are coupled with a sacri cial wax topcoat that is renewed yearly in the case of Morse. Since 2003, two types of cyclically renewable wax topcoats have been used by CPC's conservators: 1) Boston Polish™, also known as "butchers" paste wax, a carnauba-based wax, in use from 2003 to 2006; 2) Renaissance microcrystalline wax™, a mixture of Cosmoloid H80 and BASF A wax [22][23], used from 2007 to date for protecting outdoor bronze sculptures in Central Park.…”

“…It seems plausible that the water enriched with these ions could become aerosolized by the constant tra c whisking by and deposited onto the bronze. Thickett and coauthors [22][23] have demonstrated that water may be retained at the interface between the super cial layer of Renaissance wax and the coating underneath, further enhancing the corrosive attack. On ferrous metals, like steel, the prolonged exposure to this trapped moisture after the protective period of the coating might increase the rate of corrosion.…”