On the surface, critical cleaning/contamination control and art conservation seem worlds apart. Scratch the surface (or, better still, avoid scratching the surface) and you find parallels between critical cleaning and art conservation. As a point of clarification, conservation encompasses actions taken toward the long-term preservation of cultural property. In contrast, restoration is a type of conservation treatment. It specifically refers to an attempt to bring cultural property closer to its original appearance. A primary task in the conservation of paintings is to remove accumulated contamination (surface dirt, discolored varnish, or non-original paint) without undesirable change in the aesthetics. Manufacturers would say that the goal is to clean without negatively affecting the original surface. Those concerned with contamination on or embedded in coated surfaces and manufacturers of components containing plastics or composites, can benefit from the approaches of the art conservator.

CUSTOMIZED CLEANING
In contrast with critical cleaning or industrial cleaning, where commercial cleaning agents are used, the conservator acts as a formulator, preparing cleaning agents customized to the task at hand. One of the tools that conservators use to manage the chemistry of their cleaning solutions is the Modular Cleaning Program (MCP), developed by Chris Stavroudis, our co-author for this month’s column. The MCP is an interactive database computer program that incorporates chemical and physical properties of constituent materials. The MCP can be used to “fashion” a solution that is optimally suited for soil removal. It can be used for cleaning with solvent, solvent gels, or water-based systems. The system is complex. For example, parameters of the current MCP for aqueous cleaners include pH, ionic strength, gelling agents, surfactants, and chelators (and the next version will include osmotic modifiers and organic co-solvents).

One of Chris’ latest projects is to modify the MCP to assist the conservator in the cleaning of acrylic paint surfaces. Acrylic paints, emulsions of pigmented acrylic plastic particles in a water-based carrier, are the basis of most water-based paints for architectural coatings and have been used in the art world for about 50 years. After half a century, some works of art are candidates for conservation. Since many industrial products also have acrylic coatings, or coatings with similar properties or are constructed from plastics, the techniques of the art conservator are of global value.

THE YIN AND YANG OF ACRYLIC PAINTS
Acrylic paints are chemically and physically complex. Simple paints consist of a pigment to provide color and a binder to provide both cohesion and adhesion. In contrast, most acrylic paints are complex mixtures containing a number of chemical modifiers. The modifiers impart some of the visual and physical properties such as viscosity, improved film formation, pigment wetting, and extenders to reduce the amount of pigment necessary. One reason that acrylic coatings are valued is because, once the water carrier evaporates, the coating is stable and is relatively impervious to water. The key word here is “relatively” because water can affect the acrylic.