There is no fixed rule as to size of drawing or reduction, but if the designs are drawn for one-third reduction there will be no material alteration in values when produced. But as the reduction is increased there is a proportionate risk in alteration of values. It is desirable to bear the proposed reduction in mind and to work more boldly or with thicker lines, otherwise the final effect may be thin and weak. In pen drawing, the lines should be clear and distinct whatever their thickness. For designs in black and white, hot-pressed paper, Bristol board or smooth card are most suitable. The ink should be waterproof, as, if necessary, corrections with Chinese white can be more neatly made. Fine pens, except for very minute work, are not desirable, a Gillott’s ladies’ fine writing nib yielding as fine a line as is ordinarily required. For some classes of work a brush will be found more suitable, but care should be taken that all lines--whether thick or thin--are equally black. Designs in colour for illustration or advertisement, which are to be reproduced by lithography or the three-colour process, can be on card or Whatman paper. The colours employed being transparent or opaque, whichever is more suitable to working and effect. Larger designs for advertisement, such as posters, are usually painted in tempera or opaque colour, and these should be applied as far as possible edge to edge, overpainting being avoided. _Opaque Colour_ Care should be taken in mixing the colour to the required tint or shade. This requires some experience, as when white forms part of the mixture, the effect when dry is always lighter and colder than when the paint is in the fluid state; therefore allowance for this should be made. Opaque and tempera colours are not used so fluid as ordinary transparent water colours, and if applied too thin will fail to cover the surface solidly, or dry blotchy. Cartridge paper is not only good enough but more suitable for opaque colour than papers of better quality. Not merely is there no advantage in these, but the texture is an unnecessary embarrassment; moreover cartridge paper can be obtained in continuous form of good width. _Enlarging and Reducing_ When drawings are enlarged or reduced, the linear dimensions and not those of the area are implied; thus one half means one half of both width and height--really one-fourth of the area. It is obvious that half the area would be a different proportion, and it is the proportion that is concerned. [Illustration: No. 286. Diagonal Method of Enlarging or Reducing. Solid line shews given size.]