Milky, Cloudy, Foggy, Blooming Varnish and Shellac
Varnishing defects caused by milky, foggy, cloudy, and blooming looking varnish.
¶ Milky, Cloudy, Foggy, Blooming Varnish and Shellac. As the descriptive terms imply, this defect amounts to a clouding1 of the varnish transparency. In spots the varnish takes on irregular, mottled opalescent effects. The cause is nearly always the presence of moisture from damp air, spilled water, hot dishes on table-tops and in shellac varnish, which is very easily discolored by moisture. The rubbing of the coat with pumice and water instead of pumice and oil will turn it white in places.
¶ A common cause of this trouble is foggy, misty weather which produces moisture-laden atmosphere in rooms where varnishing is done. During such weather windows must be closed during and after the varnish is spread and until the varnish is hard dry, if these defects are to be avoided. They are much more likely to happen to short-oil, quick-drying varnishes than to others because they do not contain sufficient oil to repel the moisture which is absorbed by the varnish gum.
¶ The lack of ventilation in rooms where varnishing is being done invites blooming, clouding, etc., especially in new buildings where there is an excess of moisture which collects on the surface.
¶ By increasing the ventilation and rubbing the dry varnish with a soft cloth or chamois skin to clean and warm it up, the blooming will often be removed. Sometimes if the surface is rubbed with a soft cloth which has been wet with denatured alcohol and squeezed and shaken out dry it will help remove the discolorations.
¶ When shellac finished surfaces turn white the milky clouds are due to moisture absorption. Brush on a coat of denatured alcohol with a light touch. Let it dry. That will redissolve the shellac and eliminate the white clouds as a rule. Next brush on a thin coat of boiled linseed oil and wipe off gently immediately. Let it dry and put on a coat or two of varnish of good quality.
¶ Varnishes in which the oils and gums are not perfectly fused together are apt to show a bloom in humid atmospheres.
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