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Table 2 List of cleaning solutions and delivery systems evaluated on mock-ups and discreet areas of Whaam!, with preparation, application and clearance strategies

From: Reviving WHAAM! a comparative evaluation of cleaning systems for the conservation treatment of Roy Lichtenstein’s iconic painting

Cleaning systemsTailored optionsPreparationApplicationClearance
Aqueous solventsDeionised water; buffered waters with a pH range of 5.5–6.5Buffered waters made with citric acid, -(N-morpholino) ethane sulfonic acid (MES) and sodium hydroxide accordingly to The Modular Cleaning ProgramaApplied with hand-rolled cotton swabs rolled over the paint surface up to 10 times, to cover an area of approximately 1 cm2Deionised water (pH 5.5, conductivity 4 µS/cm) = DI water
Non-polar solventsShellsol D40 [Ben-Day dots mock-up only]; cyclic silicone decamethylcyclopentasiloxane (D5)Not requiredAs aboveNot required
Aqueous-based solutionsTri-ammonium citrate (TAC); non-ionic surfactants ECOSURF™ EH-6, ECOSURF™ EH-9, BIO-SOFT® BS1 and BS2Aqueous-based solutions were prepared by weight with DI water. The concentration of the TAC ranged from 0.5 to 2% w/w; solutions containing non-ionic surfactants had a concentration of 0.5–1% w/wAs aboveDeionised water (pH 5.5, conductivity 4 µS/cm) = DI water
Polysaccharide-based gel [rigid]Agarose (3% w/w)
Gellan gum (3% w/w)
Disperse the polysaccharide powder in deionised water, heat the solution at ~ 95 °C under stirring. The hot solutions were then poured into a flat container of the desired thickness and allow to cool (and gel) at room temperatureCast gels cut in to small pieces (~ 1.5 × 1.5 cm). Before application, excess water was blotted onto Whatman filter paper, and left in contact with the mock-ups surface initially for 1 minNot required as used as hydrogel only
Excess water released onto surface removed using a dry cotton swab
Silicone emulsifiers [spreadable]Velvesil Plus; Shin-Etsu KSG 210; Shin-Etsu KSG 350z—aqueous phase 20% w/wPrepared with 60% w/w silicone emulsifier, then thinned with D5 solvent (to 80% w/w), with an aqueous phase content of 20% w/w—either deionised water or with added chelators and/or surfactants. The aqueous phase was dispersed through the diluted emulsifier drop by drop and stirred vigorously to create the emulsionbApplied by a soft brush, creating a uniform layer over the surface, and left in place for 1 minDry cotton swab first (to remove the majority of emulsifier) and D5 silicone solvent-dipped swabs rolled onto the surface until visible residues were not detected (average 3–4 applications)
Nanorestore Gel® hydrogels or loaded with an aqueous-based solution [flexible]Nanorestore Gel® Extra Dry (now MWR)
Nanorestore Gel® Peggy 5
Nanorestore Gel® Peggy 6—aqueous content ~ 90%
Gels dispatched ready for use as sheets (~10 × 15 cm), immersed in a small volume of demineralised water; rinsed by immersion in DI water for 24 h before usec
After rinsing gels were pre-loaded with the cleaning solutions by immersion for 12 h
Blotted using Whatman filter paper; 1.5 × 1.5 cm gel pieces were placed on mock-ups for 1 min; light finger pressure was applied to optimise adhesion and to remove any air bubbles formed. The gels were gently peeled away from the surface, with no mechanical action requiredNot required for pure hydrogels. When uploaded with active agents, clearance involved the application of corresponding Nanorestore Gel® hydrogels for the same period. The gels can transfer a thin layer of liquid on to the surface, which can be removed by blotting the gel well before application; equally the paint surface can be lightly blotted after application if appropriate
  1. ahttp://cool.conservation-us.org/byauth/stavroudis/mcp/
  2. bNote that formulations for KSG-350z systems now generally have 10–25% emulsifier, 25–40% D5 solvent and 30–50% aqueous phase for sensitive painted surfaces; hence the KSG system used in this study was relatively emulsifier-rich
  3. cUpon arrival, the gels were transferred to closed containers (i.e. plastic or glass containers with lids used for food storage) and immersed in deionised water for 24 h; the water was changed once. In these conditions, the gels are stable and can be stored at room temperature and in the dark for several months. After rinsing, and blotting, the gel can be used as it is (i.e. as a hydrogel) or loaded with an aqueous-based solution (and some polar solvents) by immersion in the required cleaning solution for at least 12 h. Guidance on the use of the Nanorestore Gel® series can be found here: http://www.csgi.unifi.it/products/gel.html