Quantitative Measurement of Organic Solvent Retention and Residue
During the gel residue research, it became apparent that updated comparative testing was needed on the main traditional cleaning method—organic solvents—in order to compare and put the gel residue experiment results into perspective. The results supported previous studies that found long-term residency of some of these solvents. However, the gels project experiment found that residue concentrations from free solvents on the cleaned paint surface in some cases exceeded those of solvent gel formulations in a comparable cleaning situation.
- A cleaning experiment took place in June 1999 in which ten commonly used organic solvents and solvent mixtures, radioactively labeled, were applied to samples from the same painting used for the gel residue tests—the same methodology that was used to analyze the gel-cleaned samples. Samples were taken at intervals from one hour after cleaning to fifteen weeks, and radioactivity levels measured in the scintillation counter.
- Small quantities of each solvent were placed in a preweighed beaker, and weighed at intervals during evaporation. Any residues were measured by the change in weight after evaporation, and then analyzed by GC-MS to identify their nature.
- The results were compared with those of the cleaning experiment on painting samples to determine the difference in the quantity of residue left by each cleaning method.