Richard Wolbers

Acrylic emulsion paint films: The effect of solution pH, conductivity, and ionic strength on film swelling and surfactant removal

Abstract To date, a limited number of aqueous conditions have been tested experimentally as potential cleaning reagents on modern acrylic paint films. Those assessed have tended to extract measurable quantities of paint film components and distort the paint films physically. In this paper the results of a series of experiments designed to examine pH, conductivity, and specific ion effects of potential aqueous cleaning solutions on a series of commercial acrylic paints are reported. A three-dimensional microscopic technique was used to characterize the physical (volume and surface roughness) changes and liquid chromatography-tandem mass spectrometry was used to characterize the chemical (extracted surfactant) changes following paint film exposure to the aqueous solution. The tested paint films in this study clearly exhibit an isotonic point below which swelling and extraction is significant, and above which the swelling and extraction is diminished. Manipulation of conductivity and the ionic species in solution can reduce both the physical film changes and surfactant extraction from acrylic paint films; while pH appears to be of limited use in controlling aqueous cleaning effects. Moreover, there seems to be a specific ion effect for both swelling and de-swelling in acrylic paint films that can be rationalized through the Hofmeister Series.

The influence of temperature and humidity on swelling and surfactant migration in acrylic emulsion paint films

It has often been observed anecdotally and implied through experimentation that acrylic emulsion paintings accumulate and entrain soils over time due to the inherent mechanical softness in artists acrylic paint films, through the presence of hydrophilic film components, and by virtue of the ubiquitous presence of surfactant moieties on these film surfaces once they dry. In the present study, it has been this last effect that we have sought to describe more fully in terms of surfactant responsiveness to both temperature and relative humidity (RH). Surfactant hydration and dehydration under varying temperature and RH conditions affects the ultimate partitioning of the surfactant at the paint–air interface, as well as the inherent size, aggregation tendencies, and solubility of surfactant in the bulk paint materials which contain components that are highly responsive to changes in temperature and RH (e.g. polyacrylic or polymaleic anhydride-type dispersal materials). In this work, analytical techniques including three-dimensional microscopy and quartz crystal microbalance with dissipation were used to add to and reinforce current understanding of the physical and mechanical changes to acrylic paint films with temperature and RH. The migration of surfactant at the film surface was studied using desorption electrospray ionization-mass spectrometry and attenuated total reflectance Fourier transform infrared microscopy.

Lichen Encroachment onto Rock Art in Eastern Wyoming: Conservation Problems and Prospects for Treatment

Since lichen encroachment onto rock art panels of an important petroglyph site administered by the U. S Bureau of Land Management in eastern Wyoming is extensive, cultural resource managers included an evaluation of the lichen problem as part of a comprehensive management program. During 1999–2001, an interdisciplinary team composed of archaeologists, conservators, conservation scientists, lichenologists studied the problems posed by lichens at this site. This contribution summarizes the results of these studies, including new approaches to the use of non-toxic, enzyme biocides, cleaning methods.

Corroded applied lead-based decoration (hyomon) on Japanese lacquer: Principles and case studies

Introduction Around 60 pieces in the Asian lacquer collection at the Victoria and Albert Museum, London, UK (V&A) have suffered in the past from exposure to an acidic microclimate during storage, leading to varying degrees of corrosion on applied lead alloy decoration. Other museums have reported similar problems [1]. A study in the late 1980s identified the role of trace elements in the lead alloy in the inhibition (by tin) or acceleration (by iron) of corrosion [2]. Since that time, no further case studies of conservation treatments on corroded lead on lacquer objects have been published. This paper outlines the historical context of lead alloy decoration on Japanese lacquer, and reviews the principles for treating this combination of materials. Case studies are presented of conservation treatments of objects with moderate and severe lead corrosion, with the aim of establishing the degree to which such objects can be returned to a displayable condition. Problems associated with the electrolytic reduction of corroded lead on lacquer are addressed through the use of a rigid gel incorporating a conductive polymer.

U.S. CUSTOM HOUSE, NEW YORK CITY: OVERVIEW OF ANALYSES AND INTERPRETATION OF ALTERED ARCHITECTURAL FINISHES

AbstractThe U.S. Custom House, New York City, was completed in 1907 by the preeminent American architect, Cass Gilbert (1859–1934). The building is recognized as an American masterpiece of integrated architectural design, engineering, sculpture, decorative arts, mural paintings, and decorative interior finishes. The U.S. Custom House is a designated National Historic Landmark and New York City Landmark. Largely abandoned in 1972, the structure has been undergoing complete renovation since 1991, including the conservation and restoration of the interior.This paper is an overview of the analyses of the original interior finishes and architectural polychromy, executed from 1910–12 by the artist-decorator Elmer Garnsey (1862–1946). These analyses served as the foundation for the program to conserve the surviving finishes and replicate the heavily damaged and almost completely over-painted architectural polychromy. However, Garnseys execution techniques were so complex and the alteration and obfuscation of co...