Solvents come in many shapes and types. Looking for solvents for a specific application can be hard, and looking for green alternatives for currently used nonbenign solvents can be even harder. We describe a new methodology for solvent selection and substitution, by applying Artificial Intelligence (AI) software to cluster a database of solvents based on their physical properties. The solvents are processed by a neural network, the Self-organizing Map of Kohonen, which results in a 2D map of clusters. The resulting clusters are validated both chemically and statistically and are presented in user-friendly visualizations by the SUSSOL (Sustainable Solvents Selection and Substitution Software) software. The software helps the user in exploring the solvent space and in generating and evaluating a list of possible alternatives for a specific solvent. The alternatives are ranked based on their safety, health, and environment scores. Cases are discussed to demonstrate the possibilities of our approach and to show that it can help in the search for more sustainable and greener solvents. The SUSSOL software makes intuitive sense and in most case studies, the software confirms the findings in literature, thus providing a sound platform for selecting the most sustainable solvent candidate.

Organic solvents remain needed for certain treatments in cultural heritage conservation and restoration, including the application of traditional and synthetic resin varnishes on paintings. This research describes a collaborative approach for selecting and testing alternative greener sustainable solvents for this purpose. With commonly used solvent xylene targeted for substitution, initial solvent suggestions were made employing the SUSSOL (sustainable solvent selection and substitution) software tool considering key physical properties of the solvents and specified safety, health and environment hazard boundaries. In parallel HSPiP (Hansen Solubility Parameters in Practice) software was employed after the experimental determination of Hansen solubility parameters and the solubility of selected resins. Fourteen alternative solutions were selected and prepared from commonly used resins for application testing on reference substrates (e.g., Leneta cards and prepared canvas test boards). This testing included (1) the assessment of essential working properties, paint film solvent sensitivity, drying and film formation, and (2) standard coating tests such as water resistance, gloss, and color measurements. Comparable reference resin solutions used as varnishes, prepared with xylene and other solvents, were simultaneously evaluated. First standardized solvent tests provided a practical assessment of the sensitivity of the paint films to the substitute and reference solvents. Varnishing tests were subsequently performed on two historical paintings in order to evaluate the working properties and esthetic qualities of the resin solutions. The novel varnish Regalrez 1094 in isoamyl acetate showed very good working properties and gave a good visual result on both paintings. The resin solution Paraloid B72 in anisole showed good visual results on both paintings, while demonstrating acceptable working properties. This study illustrated that good working properties, protective and visual film qualities could be achieved with varnishes based on typical resins in alternative solvents. Various alternative greener solvents and their mixtures can thereby be suggested for dissolving and applying these resins. The approach within this study acknowledges the individuality of an artwork, which guides the selection of the most appropriate resin solution.