Carol A. Grissom

MEASURING SURFACE ROUGHNESS ON STONE: BACK TO BASICS

Abstract Stylus profilometry, reflected-light image analysis and visual/tactile evaluation were tested as techniques for assessing roughness of abrasive-blasted stone. Measurement of microdrop water absorption time was also tested as a complementary technique. Instrumental techniques showed significant shortcomings when measuring surfaces of roughness similar to most weathered stone, as well as flame-finished surfaces comparable to tooled stone. Tactile comparison of surfaces wasfound to be a more practical and cost-effective technique. On historic masonry structures, however, soiling and uneven weathering limit the usefulness of roughness as a property to be measured in evaluating cleaning techniques.

Evaluation of Coating Performance on Silver Exposed to Hydrogen Sulfide

Abstract Twelve coatings applied to sterling silver coupons were subjected to high levels of hydrogen sulfide to test their effectiveness in preventing tarnish in indoor environments. Silver coupons were assessed over the course of the experiment using visual observation, image analysis of digital photographs, gloss measurement, and colorimetry. Acrysol WS-24, Agateen Air Dry Lacquer No. 27, HMG Heat and Waterproof Adhesive, and PVAc AYAT generally performed best. Mowiol 28-99 performed very well on some areas but was mediocre otherwise. Butvar B-98 and Acryloid B-48N were generally less effective in retarding tarnish. Acryloid B-72 and Butvar B-76 performed less well. Aquazol 500, Aquazol 500 topped with Renaissance Wax, and Renaissance Wax were least effective. Coating thickness proved to be a significant factor in coating performance.

Cleaning Marble with Ammonium Citrate

Abstract Ammonium citrate solutions were tested to determine possible damage on marble using two concentrations, four different values of pH and several variations in application. As pH dropped from values of 10 to 7, marble chips immersed in the solutions showed increasing dissolution of calcite, and polished marble tiles to which solutions had been applied showed increasing loss of gloss and brightness. The least damage to marble tiles was produced when solutions were covered during application, and single cleanings were found to be less damaging than multiple cleanings of the same total application time. Comparison with other cleaning agents – ammonium thioglycolate and ethylenediaminetetraacetic acid (EDTA) – showed that ammonium citrate solutions could be as mild as thioglycolate when used in some conditions, such as high pH and low concentration. In contrast, ammonium citrate solutions could harm the stone significantly when used in other conditions, such as pH 7 or high airflow. In these cases, the damage was nearly as much as a 2% solution of EDTA at pH 10. This study emphasizes the need to develop new cleaning products, research which can only go hand in hand with a better understanding of the various interactions taking place between cleaning agent, substrate and environment.

THE CONSERVATION OF AMERICAN WAR MEMORIALS MADE OF ZINC

Abstract Affordable war memorials featuring soldiers made of zinc were purchased by small towns throughout the United States following the Civil War, and the practice continued to a lesser extent after the Spanish-American and First World Wars. Such memorials can be generally divided into three groups defined by fabrication techniques: (1) imitation bronze statues sand-cast in pieces, assembled by soldering, painted with “bronze” paint, and placed on masonry pedestals or cast-iron fountains; (2) so-called white-bronze statues assembled using molten zinc to back unobtrusively located joins between sand-cast pieces, sandblasted to appear stonelike, and displayed on masonry pedestals or multilayered white-bronze bases that in some cases created enormous monuments made entirely of zinc; and (3) statues stamped from sheet zinc in sections, which were soldered or riveted together on metal armatures and painted. The most common zinc statue damage is breakage of the brittle cast metal. Difficult problems are presented by large white-bronze monuments, which are often distorted by the metals tendency to creep. Even more damage has been caused by ill-informed attempts at amelioration, especially filling interiors with concrete instead of installing stainless steel internal supports. Appropriate surface treatments are emphasized.

EARTHQUAKE DAMAGE TO WORKS OF ART IN THE FRIULI REGION OF ITALY

Abstract In 1976, a series of powerful earthquakes devastated the region of Friuli, located in the northeast corner of Italy. The artistic patrimony of this area was seriously damaged, provoking major conservation problems of both emergency and long-term natures. In collaboration with Italian authorities, the Istituto Centrale del Restauro, Rome(ICR), and the International Centre for Conservation, Rome(ICCROM), American conservators have been active in a number of earthquake-related conservation projects. These include: surveys of and emergency first aid to damaged mural paintings; major treatments of damaged mural paintings; a survey of earthquake-displaced objects; and the creation and operation of a laboratory for the treatment of damaged polychromed sculpture. This paper outlines some of the special conservation problems created by earthquakes and describes a number of conservation efforts to date.