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Decorating Defects - their cause and cure

Stains on Ceilings

Stains on ceilings develop from various causes, of which moisture, in some form or other, is probably the most frequent. The treatment will naturally depend on their nature and origin, but it may be observed that it is seldom any good to try to obscure a stain merely by recoating it, for it will usually work its way through, even though several coats of distemper or whiting are applied.
Water Stains.- When these are due to the continued presence of moisture, owing to some structural defect, the only really satisfactory and permanent cure is to trace the source of the damp and take the necessary steps to remedy it.
Assuming this can be done, probably the best way of dealing with the stain is to wash off the old finish, and, if this does not remove the stain, to seal it with a coat of knotting, lining paper, or paint.
When the moisture takes the form of condensation, the solution of the problem is considerably more difficult, since the prevention of condensation depends largely on the provision of ventilation, and this is usually beyond the scope of the decorator.
Condensed moisture will quickly cause the disintegration of the ordinary type of glue- or size-bound distemper, and probably the most satisfactory treatment is to wash off all traces of the existing finish and apply two coats of paint, or, failing this, of oil-bound distemper, which is better able to stand up against such conditions. At the same time, it must be remembered that, owing to the comparatively impervious nature of their surface, either of these finishes will tend to collect more moisture than will the softer and more absorbent ceiling distemper.
Smoke Stains.-These include discoloration due to fumes from coal, coke, or gas fires or stoves; it will frequently be of a greasy nature and consequently the only satisfactory treatment for a distempered ceiling affected in this way is to wash off the existing finish with a solution of soda or sugar soap.
In rooms in which the ceilings are subjected to fumes of this kind and rapidly become discolored, a paint or enamel finish is far more economical in the long run than a size or oil-bound distemper, since the former will stand up to frequent washing. If a paint finish is decided upon, a white­lead paint should not be used, owing to the risk of it darkening as a consequence of chemical reaction between the lead and sulphurous deposits. In washing a painted surface it should be borne in mind that smoke stains are usually slightly greasy by nature, and a fairly strong soda solution, followed by thorough rinsing, will be necessary before repainting.
Tobacco-tar Stains.-In club-rooms, canteens, and similar interiors, it is not uncommon to find the ceilings discolored with yellowish or brownish stains, due to the effects of tobacco "tar." The plaster ceiling acts as a kind of filter to the smoke, causing the" tar " to be deposited on the surface. Unless removed or sealed, it will bleed through super-imposed coatings, especially those containing oil or hydro-carbon solvents. Painting or the use of an oil-bound distemper directly over such stains should consequently not be undertaken.
The most usual remedy is to seal either with shellac varnish or with aluminium paint and this treatment is probably the most reliable. An alternative, which is often effective, is to use a casein-type distemper, which contains no oil. This, applied over the existing material, should cover reasonably solidly in one coat. When ordering this kind of distemper, the purpose for which it is intended should be stated, since one containing a high proportion of casein is essential to obscure the stains effectively.