The cause of an interior wall surface finished in flat colours drying bright in patches may be that the under colour was not quite dry in places; or perhaps the flatting was not evenly distributed over the work; or the colour may have commenced to set on one lap before there was time to follow on; or, yet again, the brushes may not have had all the oil colour thoroughly washed out before being put into the flatting colour. To ensure perfect work, the under coats should be brought up well, as the flatting is only for a final dead effect. Should the walls be of large area, at least three men should be employed - two to lay on the colour without intermission, and one to follow immediately behind with the stippler, doing the work without a break until the wall is finished. The woodwork, being of smaller area, may or may not be stippled. The room should be closed during the operation, but opened afterwards, and the air allowed to enter freely until the work is dry.