Painting Defects

Floatation and Flooding

Floatation or floating occurs when a paint has been incorrectly formulated with two or more different colored pigments when one of the pigments floats to the surface giving different differences. On close examination the surface appears mottled with regular shaped cells.

Flooding is similar to floatation in that one of the pigments migrates to the surface when the paint is produced using two pigments with different densities.

These defects are corrected mainly by better paint formulation.

Gassing

This is the formation of a gas, usually by hydrogen, by the reaction of reactive pigments, like Zinc and Aluminum, with acidic materials in the resin. It can be overcome by better formulation or packaging the paint separate from the pigment and mixing the ingredients prior to application.

Mould

The growth of mould on a paint film causes severe discoloration. Mould is a plant growth that requires moisture, the presence of food and the correct temperature for growth. The defect can occur on most types of paint but is most prevalent in bathrooms, kitchens and exterior walls that are in shady positions. The paints that are most susceptible are soft oil-based paints or varnishes and emulsions, especially if they are low gloss where dirt can be trapped in the film.

Often the mould growth can be killed and color removed by washing with dilute sodium hypochlorite solution taking due care as this preparation is alkaline. Safety glasses and gloves have to be worn. Before repainting, susceptible surfaces should be prepared with anti-mould preparations, like sodium pentachlorophenate and by using either paints prepared with mould inhibiting pigments, like Zinc oxide, or by using high gloss finishes. In extreme cases it may be necessary to remove the high humidity in the room by using exhaust fans.

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