To make a cheap filter for light machine oil, obtain a large ribbed glass funnel about 6 in. diameter; take a clean sheet of thick white blotting paper, and cut from it a circle 10 in. diameter, then fold the paper twice to the shape shown in Fig. 1, and open it out like Fig. 2, so that it fits the funnel. Now place the paper in the funnel and the latter into a clean can, and pour the oil into the paper, taking care that it does not flow over. The oil will filter through slowly, and will be perfectly clear and bright. When the paper becomes clogged, it must be replaced by a new piece.

Fig. 2. Inexpensive Oil Filter.