Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/433

Rh 1 to 4, which is in its turn washed of after a lapse of about two and a half hours. Should a reddish spot remain after washing off the first paste, a second layer may be applied for about five minutes.

Securing Brass Letters to Glass. Every one who uses brass letters on glass windows, and knows how often they drop off from unequal expansion, or from the too energetic efforts of window cleaners, will find the following useful: Litharge 2 parts, white lead 1 part, boiled linseed oil 3 parts, gum copal 1 part. Mixed just before using, this forms a quick-drying and secure cement.

Size, or Mordant Varnish. One of the best mordants or sizes for signs or for work to be exposed to the weather, is called fat-oil size. It should be prepared as follows: Expose boiled linseed oil to a strong heat in a pan, when it begins to smoke, set fire to the oil, allow it to burn a moment, and then suddenly extinguish it by covering the pan. This will be ready for use, when cold, but will require thinning with a little turpentine.

Softening Putty. When ordinary putty becomes very hard, it may be softened for the purpose of easy removal by keeping it moist for a short time with caustic potash or soda, or if the putty be painted with nitric or muriatic acid it will be softened in about an hour.

Specks. These are liable to appear when varnish is allowed to skin over. Some varnishes will skin over although the can is constantly corked, and this skin being broken and mixing with the varnish will cause it to look sandy or seedy. The well-known common causes of specky work may be mentioned, dust or pumice powder upon the job, dirt present in the air, particularly liable in loosely or badly built shops during windy weather, and specks or lice in the varnish brush due to a variety of causes.

Sponges. New sponges should always be soaked in warm water for several hours before being used, and the water should be changed while it is at all colored. Feel