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Tuesday, May 30 • 5:00pm - 5:30pm
(Paintings + Research & Technical Studies) Pioneering Solutions for Treating Water Stains on Acrylic Paintings: Case Study Composition, 1963 by Justin Knowles

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This collaborative case study outlines the criteria leading to the treatment of disfiguring water stains on a large-scale, acrylic dispersion canvas painting: Composition, 1963, by the British artist Justin Knowles. Decision making factors include how the ‘negative space' of the exposed acrylic-sized canvas impacted the understanding and interpretation of the work and thus influenced the treatment methodology. Investigations into the artist's practice provided an important context for a conservation treatment, which prompted an exploration into the use of agar gel as a delivery system for aqueous cleaning solutions.
Composition is a brightly colored hard-line geometric abstraction juxtaposed against an unpigmented acrylic dispersion-sized canvas. Accidental water damage produced tidal stains across the canvas, rendering it unexhibitable. In 1973 Knowles lost more than one hundred of his paintings in a studio fire, driving him into a twenty-six-year hiatus from painting. Very few of these early developmental works by this prominent contributor to the British Abstract Art movement survive, and therefore this was a significant opportunity to conserve this rare painting.
Determining the most appropriate conservation treatment was complicated by both a lack of research into the treatment of water stained canvases, and the presence of an unpigmented acrylic dispersion-size layer. Investigation into the relationship between materials and meaning in Knowles' work, along with the cleaning of acrylic paintings, textiles, and works on paper aided in the development of a tailored cleaning solution to minimise risks to original materials whilst also facilitating the reduction of the stain.
The painting materials were characterized using microscopy, IR, and UV fluorescence, FTIR spectroscopy and XRF analysis. FTIR spectroscopy confirmed the presence of a p(EA/MMA) acrylic dispersion copolymer medium in both the paint and the unpigmented size. From these investigations, six water-stained test canvases were created, light aged for two years under museum conditions[i] , and then naturally aged for one year in dark storage. These samples were used to assess the effects of twenty-two aqueous cleaning solutions, applied both in solution and through agar gel. The results were evaluated using colour measurement[ii] and through visual observations by four paintings conservators. The effect of the preparation of the agar gel and the way it was applied were evaluated through a series of studies. Potential changes to the sized canvas surface were investigated using optical microscopy, Hirox 3-D digital microscopy[iii], highlight-based RTI, Atomic Force Microscopy, SEM, and FTIR-ATR spectroscopy. The results showed changes in surface morphology, which supported the need for designing optimal methods for both the preparation and application of the cleaning systems.
The painting treatment proceeded successfully to the point where the stain was substantially reduced. Retouching was the final stage of treatment aiming to reintegrate treated areas with the original surface, focusing on matching color, texture and gloss. A number of retouching media commonly used on acrylic paint were evaluated, and a successful method was found with Aquazol 50. As a result of this applied, collaborative research, a unique and important work has been successfully returned to displayable condition.
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[i] Conditions in the light box were at ~ 28°C and 22% RH. UV was filtered out from the light bulbs. Assuming reciprocity of exposure at 200 lux for 10 hours a day for 730 days (2 years) with an average lux in light box of 7,980 lux resulted in 183 hours exposure in the light box. 
[ii] A MinoltaÔ CM-2600d spectrophotometer using CIE Lab DE*ab colorspace was used to make colorimeter measurements. The results of the colorimeter readings were evaluated in tandem with the conservator's subjective observations concerning change in colour and gloss for each test.
[iii] Hirox 3D digital microscope images were taken at Tate, London, 2016. 

Speaker(s)
avatar for Maureen Cross

Maureen Cross

Lecturer, Courtauld Institute of Art
Maureen is a lecturer in the Conservation & Technology Department at The Courtauld Institute of Art, London. She was appointed in 2005. She worked as a professional conservator at the National Museums of Liverpool, Manchester City Art Galleries and Tate before undertaking her current... Read More →

Co-Author(s)
avatar for Maggie Barkovic

Maggie Barkovic

Assistant Paintings Conservator, Williamstown Art Conservation Center
Maggie Barkovic graduated in July from The Courtauld Institute of Art in London with a Postgraduate Diploma in the Conservation of Easel Paintings. Originally from Virginia, she earned both a BA in Chemistry at Virginia Polytechnic Institute (2008) and an MA in Art History (2012... Read More →
avatar for Olympia Diamond

Olympia Diamond

Assistant Paintings Conservator, National Museums Liverpool
Olympia Diamond is the Assistant Paintings Conservator at the National Museums Liverpool, UK. Currently, she is undertaking an Art Fund supported project for the full conservation treatment and technical investigation of the Bartolomé Esteban Murillo (1617–1682) altarpiece, Virgin... Read More →
avatar for Dr. Bronwyn Ormsby

Dr. Bronwyn Ormsby

Principal Conservation Scientist, Tate
Dr Bronwyn Ormsby is Principal Conservation Scientist at Tate. She manages the Conservation Science and Preventive Conservation department and leads Tate's contribution to the Nanorestart project.

Tuesday May 30, 2017 5:00pm - 5:30pm
Regency C-D Ballroom Level, West Tower

Attendees (163)