Volume 13, Number 1, Jan. 1991, pp.3-8
Volume 13, Number 1, Jan. 1991, pp.3-8
The 1990 WAAC Annual Meeting was held October l5th through 17th in Avalon, California on Santa Catalina Island. The papers from the meeting are listed and described below, in the order in which they were presented. Each speaker was allotted 30 minutes.
Initial studies on the identification of pigments from Chumash Indian rock art sites in Southern California were presented. These rock art sites are undergoing deterioration and disfigurement from the exfoliation of the sandstone substrate, wind and sand scouring, biodeterioration from plant growth and lichen, graffiti and other vandalism, and a black crust. Analysis by x-ray diffraction and microscopy shows the pigments used are red ochre (a mixture of red iron oxides, not just the hematite form), yellow ochre, charcoal (not soot or manganese), and shell white (no objective evidence yet of white clay or white diatomaceous earth). Binding media (if any) for the rock art pigments has not been studied. Crusts on the surface of many rock art works is gypsum, evidently caused by water percolating through the rock dissolving water-soluble salts and depositing them on the surface.
Four conservators shared treatment procedures they have used or experimented with in the conservation of photographs.
Analyses were done on nine parchment samples from the Dead Sea Scrolls. Fourier Transform Infrared (FT-IR) and FT-IR microspectrometry were used to determine whether the extent of deterioration of the samples could be quantified and to identify any materials which may have been added to the parchment during preparation. Examination of the amide I and amide II absorbance band heights and positions showed indications of collagen modifications along with hydrolysis and oxidation in the samples. Three non-proteinaceous materials--chalk, talc and ammonium sulfate--were identified in the fragments in varying amounts. These were apparently either residues from the processing of the parchment or other additives. The study showed that FT-IR is a useful method for quantifying the degree of degradation of the parchment, and also for identifying the additives on the parchment.
As part of the GCI's Environmental Research Program, which is working to identify, quantify and remove pollutants in museums, the problem of formaldehyde in museum environments (especially cases and cabinets) was presented. The harm caused to artifacts by formaldehyde was illustrated. An "arbitrary" level of 30 ppb of formaldehyde was set as a level at which museums should become concerned about ill effects on collection materials. Simple and economical passive monitors for detecting low parts per billion levels of many pollutants, particularly formaldehyde, were discussed. Methods of formaldehyde mitigation were also explored.
As a result of a course held 11-29 June 1990 at the Getty Conservation Institute--"The Consolidation of Painted Ethnographic Objects"--members of the Working Group on Ethnographic Materials of ICOM met and agreed to form a library of ethnographic binding media. As part of the first stage of developing this library, information is being gathered from researchers and conservators about existing binding media collections and studies. Please see this issue's Technical Exchange column for more about the questionnaire now being distributed (page 25).
In 1923, Louis Comfort Tiffany's studio designed three 8 ft. x 18 ft. mosaics for the new First Methodist Church in downtown Los Angeles. The iridescent favrile glass tesserae, about 1/8-inch thick, were set directly into a 1-inch thick plaster slab on the wall of the church. The church was demolished in 1983, and the paper described the 11th-hour rescue of the mosaics. The mosaics were cleaned with isopropyl alcohol then faced using Japanese paper (kozo) and fiberglass fabric with PVA emulsion adhesive. A transfer support was specially designed and attached to the fronts over the facing. The gigantic mosaic panels were then cut free of the wall and hoisted out of the building. Each unit weighed about 2 tons. The mosaics were stored for several years, then were successfully reinstalled in the new Lake Merritt Methodist Church in Oakland, CA.
In this paper, the results of a three-month experiment to determine the practicality and effectiveness of using saturated salt solutions to control relative humidity in non-airtight museum cases was presented. The text of this presentation appears on page 17 of this issue.
The "Watts Towers," at 1765 E. 107th Street in Los Angeles, consist of 17 sculptures up to 100 feet high made by Simon Rodia over three decades, ending in 1954. The construction techniques are unorthodox--much of the sculpture complex is made using steel structural materials covered with wire mesh and cement, embedded with found objects. The site is now a California State Historic Park, under the management of the Los Angeles Cultural Affairs Dept. Background and history were presented, as well as details of the low-cost, computerized documentation system and careful conservation program for the Towers since 1985. This paper was presented in coordination with one by Rosa Lowinger (summary follows).
This presentation described the work that has been carried out since 1988 to find suitable materials and techniques for stabilization, repair and restoration of the Watts Towers. The main thrust of the efforts has been the preparation of a diagnostic model for determining problems, potential causes, effects and possible remedies. With this model as a guideline, a plan was implemented for testing different materials and techniques for conservation. Tests were carried out on consolidants, crack fillers, repair mortars, cleaning agents and adhesives. In addition, the model identified areas where further analytical testing was warranted to determine the cause of problems. Actual repair work to the Towers will be carried out by specially trained construction workers. This paper was presented in coordination with one by Bud Goldstone (see prior summary).
This paper was a report on the progress of the restoration of an 18th-century French painted room, originally from a private house in Paris, dating from about 1792. It was acquired recently by the Getty to be installed in the new museum. The tall, narrow panels are decorated with paintings of arabesques, classical motifs, and mythical figures in the pseudo-Pompeiian style, framed by a solid color "surround." Subsequent owners had made some modifications, and documentation of the room's original appearance has not been found. The paintings and the wood supports generally were in sound condition, but a heavy deposit of dirt, old surface coatings, and discolored or mismatched overpaint was present. Removing embedded dirt and varnish was possible with a soap made of abietic acid, triethanolamine and water, thickened to a gel consistency, as introduced by Richard Wolbers. Cleaning revealed subtle differences in the background preparation of the panels. To answer the growing number of questions about the original floor plan of the room and the original color of the surrounds, extensive study including cross-sections and scrapings of the many paint layers on the surrounds, analysis of pigments and binding media, and research in primary sources in Paris, is underway.
A group of 11 identical painting mock-ups were prepared. Each sample was given a different varnish coating. The varnishes included natural and acrylic resins, as well as ketones, a PVA, and a hydrocarbon resin currently being tested in other studies for its suitability for conservation. A survey was conducted in which the participants were asked to chose their preference, based on appearance, for varnishing a Dutch 17th-century painting and an Impressionist painting. For the Dutch painting, paintings conservators preferred the appearance given by a varnishing system consisting of a brush coat of dammar followed by a spray coat of Acryloid B-72. Both Acryloid B-72 and Acryloid B-67 were popular 2nd choices for painting conservators. Other conservators (not painting conservators) and curators who participated in the survey favored the thin mastic varnish as well as the dammar/Acryloid B-72 combination. For the Impressionist painting, paintings conservators, as well as non-paintings conservators and curators, had a marked preference for a system utilizing equal parts of Soluvar Matte and Soluvar Gloss. Many of the participants did not make a selection for an Impressionist work. The attitude that an Impressionist work should not be varnished was considered with the results. The results were statistically significant. 14 out of 20 painting conservators chose varnish types that they typically use in their work.
A major problem encountered in the conservation of ethnographic objects is the consolidation--without altering the appearance--of paint that is flaking, porous or crumbly, powdery on the surface, or in multiple layers. The following methods for addressing this problem were reviewed: different application procedures for consolidant solutions, reforming polymer films (original polymers in the artifact) by heat or solvent, the use of matting agents, the use of high-viscosity solutions, consolidation and adherence of paint in separate steps, saturation of porous flakes with hydrophobic solvents and adhering with aqueous emulsions, consolidant solutions with low-volatility solvents, saturation of the working atmosphere with solvent fumes, use of surfactants, pre-wetting of surfaces, multiple applications of dilute solutions, relaxation of brittle surfaces with high humidity, application of solutions through a permeable facing, adjusting solvent polarity, subsequent surface matting, and sprayer application of consolidant that avoids forming a coherent film. Consolidating materials worked with were poly(vinyl acetate) resins, Acryloid B-72 resin, methyl cellulose, carboxymethyl cellulose, gelatin, and certain tested emulsions.
Jane Bassett read this paper for Dale Kronkright, who could not attend the meeting. An edited version of the presentation appears on page 21 of this issue. A discussion of the practical use of insect traps as surveying tools for museums was presented.
This paper presented the measures taken at the Fine Arts Museums of San Francisco before, and immediately after, the October 1989 earthquake, as well as during subsequent months, to protect objects and sculptures from future damage should "The Big One" hit. Improvements were made in storage areas and in exhibition areas in the way in which art objects were displayed in cases. Improvements also are being made in the placement and support of sculptures and large pieces of furniture. The museum's conservators made a concerted effort following the quake to make detailed observations and records about where and why damage occurred, and where and why it did not. They have identified some particular object protection methods that did work, and they have developed for their museum a much more organized plan for responding to personnel and collection problems that they may face in the next strong earthquake. A list entitled "Emergency (Earthquake) Supplies" was handed out to the meeting participants, as well as a bibliography compiled by the J. Paul Getty Museum in April 1987 entitled "Bibliography: Earthquakes and Cultural Property."
The Friends of Mexico Foundation in Los Angeles sponsored Lilia Rivera Weber's attendance at the WAAC Annual Meeting, helping to foster stronger professional relations between WAAC members in the U. S. and our colleagues in Mexico. The historical background of Mexican altarpieces was presented. The difficult challenge of preserving and protecting these works of art, most of which are in use in non-ideal church environments, was discussed.
The objective of this panel discussion was to initiate a dialogue and exchange of information among art professionals involved in the fabrication, handling and display of contemporary oversized works of art on paper. Conservation issues and special problems in treatment particular to large-format works of art on paper were addressed in a brief introduction, including fabrication, transport, framing, and preservation of the artist's aesthetic. Artists appear to be increasingly attracted to the use of extremely large format in printmaking and drawing, an interest which is encouraged by the availability of ever-larger sizes of both archival and non-archival papers by commercial papermakers.
Toby Michel stressed the limitations and vulnerabilities inherent in the collaborative process of creating oversized prints, stressing the importance of accepting the artist's spontaneity during the printmaking process, a spontaneity which often complicates the subsequent handling and care of such works. Don Francis and Tim Anderson addressed the important and often problematic issue of the preservation of the artist's intent with respect to framing, glazing and presentation. Due to limitations in the size of commercially available framing and matting materials, archival backing materials often have to be specially created to accommodate mounting and framing.
Ron McPherson noted that in the case of the preparation of a series of recent Ellsworth Kelly prints, Plexiglas was fabricated specifically for the piece. The size of the Plexiglas needed for these pieces required an extrusion process rather than the usual casting process, resulting in a visually disturbing rippled surface.
Toby Michel noted the large dimensional changes in oversized sheets of paper that can occur due to wetting, printing, or fluctuations in relative humidity. Exposure of large sheets of paper to fluctuating levels of relative humidity can result in dimensional changes often on the order of 1/16 inch over a few hours. The production of prints with close registration demands thus becomes extremely difficult with changes in humidity. All of the panel members acknowledged that oversized works of art on paper are more difficult to keep in good condition once produced, due to handling, storage and vulnerabilities of the paper in such large format. The discussion underlined the great amount of information available to conservators that can be exchanged in dialogue between professionals involved in the fabrication of works of art.
This paper outlined the conservation of a Roman marble well font, a Renaissance limestone relief, and a Graeco-Roman marble sarcophagus. Some of the procedures discussed include the facing and removal of the relief from a 13-inch-thick concrete retaining wall, the design and fabrication of a new stand for the sarcophagus, disassembly of the well font for the removal of iron pins, various cleaning processes including iron stain removal, and the development and application of a filling and inpainting technique for outdoor use on marble. This fill and inpainting technique involved the use of Hxtal (Crystal Plus or Nyl-1) epoxy, Cabosil fumed silica, and Thompson's #5 enamelists' glass powder. The resulting putty is isolated from the marble with Acryloid B-72. The Hxtal Epoxy can be obtained from Conservation Materials Ltd, Post Office Box 2384, Sparks, NV 89431. Glass enamel powder can be purchased from Thompson Enamel, 650 Colfax Ave., Bellevue, KY 41073. For further information regarding any of the above projects, contact John Griswold at 805/565-3639.
The state of Alaska has shown a strong commitment to the conservation of cultural property for 14 years. Currently, the state provides consultant services to regional museums and private individuals, sponsors training workshops, surveys specific collections, reviews conservation contracts by out-of- state conservators, treats state-owned material, and acts as a central resource on conservation for Alaska. The state's Long Range Conservation Plan and current conservation activities and facilities were discussed.
One of the objects damaged in last year's quake was the very large and valuable--but relatively modern (Shanghai 1918)--Chang Wen Ti jade pagoda. When the museum's insurance company's invited expert recommended a plan of repair (have damaged areas recarved by Chinese jade workers) that ran counter to our ethics and wishes (restore the pagoda using the fragments), ethical, cultural and technical questions were raised. These issues were discussed.
In 1972 it was learned that pulsed laser radiation is capable of divesting black encrustations of sulfation from exceedingly friable marble sculpture. Subsequent laboratory investigations revealed that laser parameters (viz., pulse width, wavelength, and fluence) may be selected that virtually eliminate damage to even the most fragile stone. As a consequence, laser cleaning was found capable of producing a patina that is superior to that resulting from conventional chemical and abrasive divestment. For the past decade, field experiments have been performed in Italy and China to assess the practical issues associated with laser utilization at challenging building preservation sights. These experiences led to the fabrication of two rather basic and rugged YAG lasers that were placed in operation at the Cremona Cathedral and Xian warrior restoration sites in 1989. The most important Wilgelmo statues of the Cremona facade (the 12th-century door) were cleaned by laser. For complete divestment, each statue required approximately one million laser pulses taking one month to deliver. The greatest difficulty encountered was that of electrical voltage drop over long extension cords. High-power electronic regulators were acquired that remedied this situation. Scaling studies indicate that a typical industrial laser (at 10 times the capital cost) would be able to accomplish the same work in about one day. Real-time plasma spectroscopy has demonstrated automated process control for the project in Xian.
The Rocky Mountain Regional Conservation Center (RMRCC) is a self-supporting, non-profit department of the University of Denver, providing a full range of high-quality conservation services to public and private institutions and individuals. They are committed to the professional preservation of paintings, paper, textiles, and objects. The RMRCC is unique because it is the only regional conservation center providing conservation services in these four areas. The RMRCC's relationship with the University of Denver was discussed, and brief case histories illustrating the benefits of collaboration within the RMRCC were presented.
The concentration of binding medium in gesso is an important parameter for studying historical artist or workshop techniques. This paper presents a rapid method for quantifying binding medium in gessos using Fourier Transform Infrared Spectrometry (FT-IR). Four types of gessos (CaC03-rabbit skin glue; CaC03-gum arabic; CaS04-rabbit skin glue; CaS04-gum arabic) were prepared with concentrations of binder ranging from 0.5-50.0 percent w/w. Binding medium content in the gesso standards was verified using thermogravimetry. The peak heights of binder and pigment in the FT-IR spectra were ratioed to establish a calibration curve. The curve was used to quantify the amount of binder in museum samples.
Linseed, walnut and poppyseed oils obtained from various suppliers were classified according to their fatty acid profiles, using combined gas chromatography-mass spectrometry. The results indicated that, for a particular oil, the ratio of palmitic to stearic acid concentration (P/S) is affected by heat aging and ultraviolet light exposure. The variation in P/S ratio is also affected by the method of pre-treatment of the oil. Included in this paper is a discussion of a method of sample preparation which greatly reduces the overall analysis time.
This paper discussed the treatment of a topographical engineer's coatee, one of only seven such known in existence, worn to survey the western US in the first half of the l9th century. The fragile condition of the costume (in particular, the shattered silk lining), together with the problems of potential long-term exhibition, made the treatment a complicated one. In an effort to find a solution, the assistant curator of the museum and two conservators were consulted. The solution is a compromise, and the success of this treatment can only be evaluated in time.
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