Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/314

306 It must also be borne in mind that this process is not to be a universal scraping; it is merely remedial, to remove any excrescences which may exist, but its purpose is not to scrape or plane the wood. This is supposed to have been already done by the carpenter, and if it has not, a tool different from the stopping knife should be used.

The dusting brush, generally called the duster, must be freely used during this process so that all the particles scraped off may be removed. The largest of the brushes used for painting is sometimes employed as a duster previously to being devoted to its proper purpose, in order that it may be rendered softer; but this is not a good plan, for a certain amount of dust necessarily finds its way up the brush, and is liable to work out when it is being used for painting purposes, thus giving the work a coarse and gritty appearance and causing much annoyance.

The next stage of preparation is that called knotting, the purpose of which is to guard against the knots appearing in the finished work, by stopping their absorbent quality, or closing the apertures of the fibre, and thus preventing the effusion of gum or sap. It is, of course, strongly urged that wood should be thoroughly dry before it is used, but this is not within the power of the painter to control; he must take the wood as he finds it, and must do his best to counteract the effects of the new wood on his work.

It must be remembered that in the knots the ends of fibres, which are so many open tubes, are exposed, and thus, if all the sap or gum has exuded, they will present spots very much more absorbent than the surface of the board itself, whilst if the wood be new and the gum and sap flesh in it, these will from time to time exude and force off the paint, or cause it to become sticky.

Patent Knotting may be purchased at the color shops, and the following are two excellent recipes for making