CCI is pleased to provide internship opportunities to students and graduates of conservation programs. Not only do these individuals get to hone or acquire new skills and research directions, but they add to CCI's knowledge base. Starting with this issue, the CCI Newsletter will highlight the work of some recent interns.

Dr. Emilio Cano Díaz (a graduate student from the National Center for Metallurgical Research in Madrid, Spain) worked in the Preventive Conservation Services Division with Jean Tétreault from July to December 2000. The study he undertook at CCI was a team project that included Maarten von Bommel (Netherlands Institute for Cultural Heritage, the Netherlands), Dr. David Scott (Getty Conservation Institute, United States), Dr. Luc Robbiola (École national supérieure de chimie de Paris, France), and Dr. Jean-Pierre Dallas and Dr. Marie-Geneviève Barthes (Centre National de la Recherche Scientifique, France).

The purpose of the project was to study the corrosion of copper and lead in environments rich in carbonyl vapours. [Carbonyl compounds include harmful vapours such as formic and acetic acid as well as formaldehyde; this is significant to museums because display and storage environments are often rich in carbonyls.] Emilio's role was to prepare about 200 samples of lead and copper, and then measure weight and colour changes of the samples as corrosion progressed. A chromatographic technique was used to monitor the levels of carbonyls; other techniques used in the study included X-ray diffraction and X-ray photoelectron spectroscopy.

Lead corrodes more quickly than copper in the presence of acetic acid vapour at levels higher than 0.1 parts per million (ppm), which can easily be reached in museum situations if various display and storage materials (e.g. wood, fresh paint, white glue, and acid-type silicone) are used incorrectly. However, preliminary test results showed that if lead was exposed to formic acid, stable compounds that minimized further corrosion would form on the surface.

Copper, on the other hand, corrodes more quickly than lead in the presence of formic acid vapour levels above 2 ppm (which can easily be reached in display cases that are coated with oil-based or alkyd paints). And unlike lead, copper exposed to formic acid does not acquire a stable surface film. As a consequence, such exposure results in ongoing damage.

Emilio Cano Díaz prepares metal samples for exposure to carbonyl vapours.

Irene Karsten cuts samples of adhesive films before measuring their tensile properties.

In research that is still underway, X-ray diffraction and X-ray photoelectron spectroscopy analysis will help to identify the composition of the compounds that build up on the surface of lead and copper as it corrodes. Increased understanding of the causes of rapid corrosion of copper and lead in carbonyl environments will help conservation scientists, environmental consultants, and conservators to improve control strategies.

Irene Karsten (a doctoral student in textile conservation science in the Human Ecology Department at the University of Alberta) worked in the Conservation Processes and Materials Research Division with Jane Down during the summer of 1999.

Irene's previous work had suggested that relative humidity (RH) during the drying process can affect the quality of adhesive coatings on sheer fabrics that are used to support textiles, as well as the stiffness and peel strength of silk textiles that are heat-sealed to these supports. Her goal at CCI was to test the theory that RH during drying can influence the properties of adhesive films. The work involved preparation of adhesive films at five different RH levels ranging from 6 to 85%, and measurement of their tensile properties and gloss after the films had dried.

Measurements were taken after 1 day and after 4 weeks of conditioning in an ambient laboratory setting with 50%RH. After 1 day of conditioning, dispersion adhesive films that had been dried at very low RH levels exhibited lower gloss, lower tensile strength, and higher elongation at break than films that had been dried at very high RH levels. The differences in tensile properties disappeared after 4 weeks of conditioning in 50%RH, but the gloss differences persisted. Preliminary tests of adhesive films cast over polyester Tetex indicated that these differences in tensile properties could affect the integrity of the adhesive coating if the fabric was pulled off a Teflon-coated glass cloth release surface immediately after adhesive drying.

Clearly, therefore, RH is an important factor to be considered during the preparation of an adhesive-coated support fabric for textile conservation treatment. The results of this study, along with Irene's previous work that revealed the problem, will eventually be published in detail in the conservation literature.

Some other interns who have been at CCI in the past 6 months include:

Elizabeth Berry: A graduate of the Collections Conservation and Management program at Sir Sandford Fleming College. October 2000 to April 2001 in the Treatment and Development Division - Objects with Tom Stone.

Sarah Brett: A graduate of the Collections Conservation and Management program at Sir Sandford Fleming College. February to November 2001 in Learning and Development with Sonya Milly.

Wing-Fai Lai: A graduate of the Hong Kong University of Science and Technology and presently a conservator at the Hong Kong Museum of Art. January to December 2001, a joint internship with the Treatment and Development Division (with Bob Barclay) and the Preventive Conservation Services Division (with Jean Tétreault).