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CCI Newsletter, No. 38, 2007

Small-scale Tests for a Large-scale Project: First Steps for Cleaning the Decorative Stage Curtain at the National Arts Centre

by Jan Vuori, Renée Dancause, and Janet Wagner, Textile Conservators, CCI

Figure 1. Detail showing the knotted nylon monofilament structure of the curtain.
Figure 1. Detail showing the knotted nylon monofilament structure of the curtain.

Figure 2. Southam Hall, National Arts Centre, c. 1969.
Figure 2. Southam Hall, National Arts Centre, c. 1969.

Figure 3. Detail showing superimposed layers of net and underlying reflective metallic curtain.
Figure 3. Detail showing superimposed layers of net and underlying reflective metallic curtain.

Figure 4. CCI Textile Conservator Janet Wagner conducting cleaning tests on the curtain.
Figure 4. CCI Textile Conservator Janet Wagner conducting cleaning tests on the curtain.

The decorative stage curtain that hangs in Southam Hall at the National Arts Centre (NAC) in Ottawa is a Canadian icon. Created by Canadian fibre artist Micheline Beauchemin, this spectacular curtain was unveiled in 1969 as one of the artworks commissioned for the newly built centre. But after 35 years the curtain required cleaning and restoration. In October 2004, Gerry Grace, Archives and Exhibitions, NAC, contacted CCI for assistance in returning the curtain to its previous grandeur.

The curtain is large and heavy [approximately 24.4 m (80 ft.) wide by 12.2 m (40 ft.) high, with a weight of about 1455 kg (3200 lbs.)], and complex in structure. It consists of two sections that are lowered into place from above. Various lengths of dyed nylon net, made from a knotted monofilament similar to fishing line, cascade down the surface in loops of varying width. The multicoloured effect is enhanced by sections of differently coloured net that are layered over most of the surface, one atop the other. The layers of net are backed by a shiny metallic fabric that reflects light back through the coloured net, increasing its brilliance and luminosity.

Over the years the net had acted like a giant air filter, accumulating a layer of disfiguring dust and dirt. In addition, a few areas had become snagged and torn. The time had come for the curtain to be cleaned and repaired.

Opportunities to examine the curtain were limited by the busy performance schedule on stage. It was not until December 2004 that a team of CCI textile conservators and scientists could inspect the curtain, carry out preliminary on-site cleaning tests, and take representative samples of the net for further study.

The first phase of the project involved testing and analysing the samples.

We conducted practical cleaning tests using a variety of methods and reagents: vacuuming with brush attachment; wiping with a dry conservation sponge; wiping with aqueous solutions of an acid, base, alcohol, or detergent or with an organic solvent. Vacuuming followed by the application of aqueous solutions combined with mechanical action was found to be effective in removing the bound soils. However, whether or not the aged nylon could tolerate the use of moisture in the cleaning process required more study.

Scientific analysis and testing of the nylon net in a similar work of art, Le fils des étoiles, also by Micheline Beauchemin and dating from the same period, had resulted in a decision to avoid the use of moisture.1 But Le fils des étoiles had been on permanent display for many years, and the constant exposure to light had weakened its nylon net. Because the NAC curtain had received very limited exposure to light, we expected its condition

Multiple tests were subsequently carried out on the samples:

  • infrared spectroscopic analysis by Scott Williams identified the net as Nylon 6 and revealed that the dirt was composed mainly of different proportions of calcium carbonate, sulphates, and silicates; it also confirmed the efficacy of the practical cleaning tests

  • tensile tests by Season Tse assessed the effect of wet cleaning on the tensile properties of the nylon filament

  • thermal analysis by Gregory Young assessed the effect of wet cleaning on the moisture content of the nylon

  • X-ray microanalysis and scanning electron microscopy by Jane Sirois documented the chemical and physical surface condition of the nylon filaments

The results of these tests indicated that the nylon was weaker and stiffer than it had been when new. However, we concluded that it could safely withstand gentle cleaning with careful manipulation and short duration wetting. We also noted that the condition of the nylon was not uniform among all colours, which meant that some colours would require even more caution during cleaning.

The second phase of the project — on-site practical cleaning tests on the curtain itself — was carried out in November and December 2005. The goal was to establish a protocol that could be used to clean the curtain effectively, efficiently, and safely while taking into account its enormous proportions and complicated structure. Armed with the knowledge from the previous work, we tested a variety of cleaning methods. Wet–dry industrial vacuum cleaners equipped with HEPA filters and slot nozzles customized with natural horsehair bristles were found to be very effective for removing the bulk of the dirt. Tenacious dirt required subsequent wiping with microfibre cloths dampened with water and/or dilute acetic acid followed by a rinse with another dampened cloth. Once cleaned the net positively sparkled and its colours appeared brighter and more saturated.

The results of the cleaning tests were discussed with NAC staff and with the artist, Micheline Beauchemin. All parties agreed that the method outlined above should be employed and that the curtain should be cleaned in situ in its vertical position. The NAC is currently developing a strategy to carry out this monumental cleaning project in conjunction with a private-sector conservator. The cleaning of the curtain will be no small task and will take many hours to complete — but our tests indicate that the results will be well worth the effort. In the future, regular vacuuming and the use of a dust cover to house the curtain when it is not in use should protect it from further deposits of dust.

The NAC hopes to establish a house practice of having the restored curtain in place on a regularly scheduled basis throughout the programming year. This will allow future audiences to enjoy the brilliance of this spectacular curtain once again. CCI is very pleased to have contributed towards this goal.

  1. Little, S. “L’art de la fibre de nylon: Le defi d’un textile architectural contemporain.” pp. 736–740 in ICOM Committee for Conservation 13th Triennial Meeting, Rio de Janeiro, 22–27 September 2002: Preprints, Vol. 2. London, UK: James & James, 2002.