Effect of paint on vapour resistivity in plaster

• Main Author: L. de Villanueva
• Format: Article
• Language: English
• Published: Consejo Superior de Investigaciones Científicas 2008-12-01
• Series: Materiales de Construccion
• Subjects: gypsum; plaster; vapour permeability; paints; thermodynamic calculations
• Online Access: http://materconstrucc.revistas.csic.es/index.php/materconstrucc/article/view/119

The vapour resistivity of plaster coatings such as paint and their effectiveness as water repellents were studied in several types of plaster. To this end, painted, unpainted and pigmented specimens were tested. Experimental values were collected on diffusion and vapour permeability, or its inverse, water vapour resistivity. The data obtained were very useful for evaluating moisture exchange between plaster and the surrounding air, both during initial drying and throughout the life of the material. They likewise served as a basis for ensuring the proper evacuation of water vapour in walls, and use of the capacity of the porous network in plaster products to regulate moisture content or serve as a water vapour barrier to avoid condensation. Briefly, the research showed that pigments, water-based paints and silicon-based water repellents scantly raised vapour resistance. Plastic paints, enamels and lacquers, however, respectively induced five-, ten- and twenty-fold increases in vapour resistivity, on average.