The procedures of cleaning cultural heritage objects are evolving each year. In the past, the primary method of cleaning involved the use of organic solvents, which are harmful to the environment and people. Presently the use of colloidal systems is the main method in the conservation-restoration procedures. These systems minimize the usage of toxic solvents and decrease the chance of damaging the objects we clean. An example of colloidal systems are gels. These are systems of at least two components: a polymer and a fluid that fills the polymer mesh. The fluid can either be a solvent or a microemulsion, which is a stable colloid dispersion of two fluids that don’t mix, where one is dispersed in the other. Gels, solvents and microemulsion are chosen specifically for each cleaned object. It is crucial that the object stays undamaged and that no residues of gel remain on its surface. A special type of gel is poly(vinyl) alcohol hydrogel. Its characteristics can be modified by different methods of synthesis, which are cast-drying and freeze-thawing by one or more cycles. Besides different synthesis methods, the addition of poly(vinyl) pyrrolidone also affects viscoelastic characteristics and the release of fluid. Poly(vinyl) pyrrolidone increases the porosity of the hydrogel.
|
