Sketching and Rendering in Pencil. E-book. Formato PDF Arthur Leighton Guptill   -  Forgotten Books, 2017  - 

Brush — A soft brush is needed for keeping the drawing free from dust as tiny specks often cause spots and streaks as the pencil passes over them. The paper should always be dusted with care after erasing is done. Boards — It is usually well to fasten the drawing to a board of convenient size with thumb tacks. Be sure that the board is very smooth, for unless it is so or the paper very thick, the grain of the wood may show in the final drawing. When us ing thin or medium-weight drawing paper it is best to put an extra sheet or two under the drawing to insure a good surface.