Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/297

Rh meanwhile only in one direction. In a short time the paste will begin to thicken, which means that it is cooked, and is then about right for use. In order to stiffen the paste, and also to prevent it becoming rancid, alum is sometimes added in the proportion of about a teaspoonful of ground alum to two quarts of paste, this, however, must never be added if the paper to which it is to be applied is ingrain, as it is likely to cause the color to fade. It must also never be used on gold papers, as it turns the so-called gold black. To preserve the paste a few drops of oil of cloves should be added, or a little carbolic acid. An excellent preservative is formaldehyde, which may be added in the proportion of about a teaspoonful to four quarts. The paste should not be used while hot, it is better if it stands for a little time. To prevent a skin forming on the top a little cold water may be added. If the paper is a very stiff one, a small proportion of glue melted in water may be added, but this is not, as a rule, necessary.

Measuring Quantity of Paper Required. It will now be necessary to ascertain the number of pieces of paper required for the room that is to be re-papered. Paperhangers can, as a rule, tell the number of pieces by glancing at a room, but the amateur will require to measure. A piece of wallpaper is eight yards long, and when trimmed 21 inches wide, there is, however, more or less waste, and the larger the pattern the greater will the waste be. In practice the simplest plan to follow is to take a roll of paper or a piece of stick out to the right length, and to measure around the room, and find out how many lengths will be required, then measure the height, and see how many lengths can be obtained from the eight yards in length, remembering that something must be cut to waste, so as to match the paper. The pieces left over will usually be sufficient to paper over doors, windows, and any odd places. The following table may be useful for reference, but it cannot always be relied upon, because it is clear that one room