If paint remains soft, tacky or even wet for a long time, possible causes are application in unsuitable conditions, e.g. poor ventilation, low temperature, excessive humidity, chemical pollution or application to surfaces on which there is grease, oil, wax polish or other such contaminants.Drying may also be retarded if a preceding coat has not been allowed to harden sufficiently. The use of unsuitable thinners may also retard drying.An improvement in atmospheric conditions, when they are the cause of slow drying, may allow the coating to dry eventually though it is likely that its appearance may be impaired and a further coat may be required.When surface contamination is responsible, it will usually be necessary to remove the affected material, clean the surface thoroughly and repaint.