Submitted: July 24th, 2021
Lucile Pourret, Author for the Greener Solvents Team
Conservator & Restorer of Modern and Contemporary Paintings
While working in a painting conservation and restoration studio, I realized that there were materials we used every day without really questioning their consumption. Cotton and sponges are an integral part of our practice, and I had never considered the sustainable or ecological impact of using them. Often utilized in the cleaning and varnish removal stages, these materials allow for the application of solvents and aqueous solutions, as well as dry cleaning and dusting.
Below lists some types of materials used in conservation-restoration operations,  :
I was interested in the type of cotton that we use for cleaning paintings and for varnish removal. Small amounts of cotton, wrapped around a wooden stick, that form an applicator for the chosen solution. Once the applicator has absorbed the dirt, or the solubilized varnish, it is discarded with no possibility of reusing or recycling because of the resins and solvents present. Between 2 and 5 kg of cotton are used each year in our studio (about 3 packs of 100g per month). n Cotton wool comes from the transformation of cotton seeds by an industrial process and is ubiquitous in the textile industry . It is currently the world’s leading natural fibre in terms of production volume, and represents approximately 2.5% of the world’s cultivated surfaces. The majority of cotton is produced in Asia and Oceania and world production in 2017-2018 was about 26.75 Mt. In 2017, 80% of the cotton crop was grown with plants genetically modified to resist caterpillars and certain herbicides to facilitate its cultivation and yield . Irrigation is used in 40% of crops, aggravating the problems of drought in the regions where it is grown (notably in Africa: Benin, Egypt) . According to the Water Footprint Network and UNESCO-IHE, cotton cultivation and processing require a very large amount of water. It takes between 2,000 and 8,000 litres of water to produce 1kg of cotton. The amount of water used varies according to the country of production. On average, it would be 2000 in China, 5000 in Pakistan and 8000 in India. With my 5kg of cotton per year, this would represent an average of 25,000 litres of water per year for a material that is disposable and hardly reusable.
Unlike cotton, the various sponges available in a conservation workshop are reusable. There are different types with different properties adapted to more or less specific uses (make-up sponges can be used for water-based and dry cleaning, for instance).
The natural sponge is historically the oldest. It is known for its absorbent properties but is less suited to the conservation field because of its irregular shape. The sponge is a marine animal that grows on the sea and ocean floor and serves as the basis for the development of many ecosystems. It dwindled in use by the end of the Second World War as it was replaced with cheaper synthetic sponges manufactured in larger quantities.
Synthetic sponges come in different types: sponges made from vulcanized rubber of natural or synthetic origin, those made from polyurethane or other petrochemical polymers, and finally, those made from cellulose obtained from wood, flax or cotton fibres. Cellulose sponges are, according to some manufacturers, biodegradable. However, other chemical elements enter into the manufacturing process such as antibacterial agents and chemical softeners. It would be interesting to find publications on the degradation of these chemical compounds in order to be able to conclude on the biodegradability of cellulose sponges.
Synthetic sponges are almost all derived from hydrocarbons and therefore from oil. The manufacturing process also requires the use of hydrocarbons, notably to vulcanize the rubber or to foam the polymers. Polyurethane sponges can emit formaldehyde during their incineration (waste treatment), which is an irritant for the respiratory tract .
In our practice, it is important to choose the most suitable materials for the artwork because it has the priority. Cotton is a material that, for the moment, remains the most suitable for cleaning the vast majority of paintings and artworks. However, we can integrate an ecological dimension into our choices and adopt the material that will have the least impact on the environment for a given artwork and action. For example, synthetic sponges or those containing chemical compounds can be used several times and sterilization allows them to be preserved longer. Re-use of cloth as a rag can be an alternative to cotton. These options should be considered and used wherever possible to reduce our ecological impact.
G. Fernández-Villa, Silvia, M. de la Roja, José, San Andrés, Margarita, Colour Change Caused by Dry Cleaning Process on Painted Surfaces, e-conservation Journal 5, 2017
 Daudin- Schotte, Maude, Bisschoff, Madeleine, Joosten, Ineke, van Keulen, Henk and Klaas Jan van den Berg, Dry Cleaning Approaches for Unvarnished Paint Surfaces
 Gourlot, Jean Paul, Bachelier, Bruno, Coton et textiles, CIRAD, Montpellier, 27 septembre 2020, available on https://agritrop.cirad.fr/596672/8/ID596672Diaporama.pdf accessed in 8th July 2021
 Bouchaud, Charlène, La culture du coton en région désertique: la culture durable?, Les nouvelles de l’archéologie, 161 / 2020, pp. 55-60, DOI https://doi.org/10.4000/nda.10591
 A.K. Chapagain, A.Y. Hoekstra, H.H.G. Savenije, R. Gautam, The water footprint of cotton consumption, Value of Water Research Report Series No. 18, September 2005, available on https://www.waterfootprint.org/media/downloads/Report18.pdf accessed in 24 July 2021
 M. Stevely, John, E. Sweat, Donald, M. Bert, Theresa, Sim-Smith,Carina and Michelle Kelly, Commercial Bath Sponge (Spongiaand Hippospongia) and Total Sponge Community Abundance and Biomass Estimates in the Florida Middle and Upper Keys,USA, 2010, pp. 394-403 available on
http://aquaticcommons.org/15479/1/gcfi_62-60.pdf accessed in10th July 2021.
 Talk, Earth, Which Sponge is Better for the Environment?, ThoughtCo, Feb. 16, 2021, available on https://www.thoughtco.com/real-v-artificial-sponges-for-the-environment-1203669 accessed in 10th July 2021.