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Home >>Professional Decorating>>Decorating Museum>>Rain marks on new Paintwork
Decorating Defects - their cause and cure
Rain marks on new Paintwork
In an uncertain climate such as we possess in certain countries, it not infrequently happens that shortly after exterior surfaces have been painted, rain falls on them, leaving disfiguring marks on the new paintwork.
The degree to which the work is marked in this way depends on various factors.
The harder the condition of the film when the rain falls on it, the better it will be able to resist marking; in consequence, a paint which dries quickly to a hard coat is more likely to be immune than one which remains tacky for a longer period. A more decisive circumstance is the kind of
district in which the work is done.
In rural areas, where the air is relatively pure, the marks will often dry out without leaving any perceptible trace, though the subsequent behaviour of the paint film may be to some extent
influenced by the partial absorption of moisture, since, it must be remembered,
a wet or tacky film of paint is more porous than one which has dried and hardened.
In industrial districts, marking may be pronounced because the rain is charged with soluble salts from the atmosphere. These, when deposited on the film, may cause a partial emulsion of the coating, if the latter is still wet, and the deposit is retained when the paint hardens.
In a good many cases there is no real cure, but on occasion an improvement can be effected by washing with plain cold water when the marks are observed, provided the film is not too tacky. In any case, no attempt should
be made to paint over the stains without washing the surface of the work and
leaving plenty of time for drying.