Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/435

Rh to keep them free from insects, use the following mixture: $1/4$ pound of lime and $3/4$ pound of sand to $1/2$ pound of soft soap. Lay it on the boards and scrub it in well, wash it off with clean water, and make it as dry as possible. If ink should be spilt on boards, it may be removed by the application of muriatic acid, and afterwards simply washed. For painted boards, either on the floor or wainscoting, nothing better or more cleansing can be used than fuller's earth, with or without soap.

Testing Plaster of Paris. The method of testing the quality of plaster of Paris is by taking a small pinch of the powder between the finger and thumb and gently rubbing it, if small particles of it are felt, grit indicates that parts of the plaster have already absorbed water, and it is therefore unfit for use. The same test may be observed by taking a pinch of the powder again and placing the fingers under water, and then rubbing the same way as before. If, however, in both of these tests no grit is felt, and under water a thin creamy substance is found, which is easily rubbed off the fingers, the plaster is in a proper condition for use.

To Clean White Marble. Mix together $1/2$ pound of pearl-ash, $1/2$ pound of soft soap, and 1 pound of whiting. Boil them until they become as thick as paste, and let the mixture cool. Before it is quite cold spread it over the surface of the marble and leave it for at least a whole day. Use a soft water to wash it off, and rub it well with soft cloths. For black marble nothing is better than spirits of turpentine.

To Perforate Glass. In drilling glass, stick a piece of stiff putty or clay where the hole is required, and make a hole in the putty the size required, reaching down to the glass. Pour a little molten lead in the hole, and if the glass is not too thick, the piece will at once drop out.

To Polish Marble. To polish marble, such as table-tops, the following mode is followed by masons: With a piece