When used, and rectified from all foreign matter and other impurities. In this condition it is accordingly volatile ; and as it evaporates it becomes thick or fatter, and greasy. In this condition it is not wise to attempt to paint with it, but it should be set aside to evaporate still more.
In time it is reduced to a thick, heavy oil, which is the commercial fat oil, sold under several names. To prevent it from collecting dust, -- and it has a predisposition to accumulate it in vast quantities, -- it is well to cover the vessel in which it is kept. A piece of perforated cardboard is good, so that evaporation may still continue. When it has reached this condition, -- that of a heavy, thick mass of oil, -- it may be poured off into a bottle, corked and kept for future use.
The spirits of turpentine in use one day may be in good condition for next day's use, but it is always more satisfactory to have it clean and fresh at the beginning of each day's work. It is a very cheap commodity, and is not expensive even when used recklessly and extravagantly. That in use today for painting and cleansing the brushes may be put aside for twenty-four hours, when it will be found to have cleared itself.
Mineral colors are heavy, and soon settle to the bottom of the vessel containing the turpentine. The vessel can then be gently tilted, and the clear
