The changes effected by contrast in altering the height of tone of juxtaposed colors is illustrated by Figure 20. Here the small inner squares are all of exactly the same tone of gray, but they appear to grow progressively darker as the outer surfaces grow progressively lighter. The same phenomena appear when dark pictures or hangings are placed against light walls, or when light rugs are placed On a darker floor. Moreover they appear whether the juxtaposed surfaces are in tones of neutral gray, in tones of the same hue, or in tones of different hues, as when a light red pillow is placed against a dark blue sofa. In the latter case, however, there is a double effect. Not only will the red appear lighter and the blue darker in tone, but each hue will also appear to be slightly tinged with the complementary of the other. That is, the red will be slightly tinged at the point of contact with orange, and the blue with green.

Figure 20.

This phenomenon, which is called simultaneous contrast and is described and illustrated in every good textbook on optics, is of less importance in decoration than in painting, because the decorative areas are larger and the textures coarser. Nevertheless it is sufficiently important to require careful study and constant watchfulness in practice. It may be observed by placing small squares of colored paper against differently colored backgrounds, or by means of lengths of plain drapery fabrics. If a piece of orange-colored velvet, for example, be held against successive backgrounds of black, white, ultramarine and green, it will seem to change color slightly with each background. Against black it will appear not only lighter but more golden, because the lighter or yellow element in its composition is more strongly accentuated by tone contrast than is the darker or red element. Against white it will appear both darker and more red, for the opposite reason. Against its complementary blue it gains in purity and brilliancy, and against green it becomes more reddish in hue, because it is tinged by the complementary of the green ground. Thus when red and blue are juxtaposed the red tends toward orange-red and the blue toward green-blue; yellow and green tend respectively toward orange-yellow and bluish green; green and blue toward yellowish-green and purple; and so on. When true complementary hues are juxtaposed each is made more brilliant by the contrast.

What is true of the spectrum colors is true of all their derivatives formed with black, gray and white, in direct proportion to the amount of white light in the color. Very light broken tones impart their comple-mentaries more strongly than do darker tones, and are accordingly better adapted for the production of brilliant or elusive color effects. Simultaneous contrast is most marked when the two hues are in about the same tone. When dark colors are used with light the effect of simultaneous contrast is very slight. Contrast both in hue and in height of tone is made very much less marked by the use of materials of rough surface, coarse texture, or conspicuous design.

In discussing tone contrast it is of course to be remembered that tones, as we have defined the word, are simply measures of relative light and darkness, the idea of hue or color proper being abstracted. We are not in this connection concerned with correct hue relationships, but with correct tone relationships, which is an entirely different matter. Thus it often happens that a color contrast entirely satisfactory as far as the hues are concerned is inharmonious because of bad tone contrast. A dull gold cushion on a dark blue davenport would be pleasing; a cushion of pale maize or primrose would not be.

Tone contrast is a factor of very great importance in interior decoration. Necessarily an element in every decorative problem, it must be carefully studied and skillfully employed. When so employed it becomes a source of beauty; when otherwise employed a source of discord and unrest. Nowhere in the art do we find a stronger confirmation of the statement that good decoration is not absolute but relative, and that the essential thing is correct relationship; for it constantly happens that a color, pleasing in itself, is so changed in tone by contiguous colors that it becomes unpleasing. The pastel or water color that blends rest fully into the background of a soft gray wall will seem to start violently from a dark wall. The low-toned Kurdistan rug that rests as peacefully upon a dark floor as if it had grown there will ruin the repose of any room in which it is placed upon a floor of light yellow oak or maple.

Contrast of tone, like contrast of line, form or hue, is essential in good decoration because it helps to ensure the diversity without which beauty is impossible. Thus tone contrast is necessary between floor and wall, wall and ceiling, background and ornament, and between the structural and non-structural parts of a room. It is however a serious mistake to make these contrasts too marked, since they inevitably tend to arouse a sense of activity and hence to be destructive of repose. Many rooms have been spoiled by too sharp contrast between floor and wall, and many more by too sharp contrast between wall and ceiling - the latter defect being very common by reason of the widespread but erroneous idea that the ceiling must always be either white or a pale cream, regardless of the tone of the walls.

Bad tone contrast appears most frequently, however, and in the form most destructive of repose and beauty, in sharp contrasts between small masses, or between a small and a large mass. The motive in carpet or wall paper which is markedly lighter or darker than its background, and therefore appears to stand out in a definite effect of relief; the ebony piano against putty-colored walls, or the large mahogany dresser against pearl or pale French gray; pale-tinted cushions against dark, heavy upholstered furniture; dark verdure tapestry papers in a frieze above white paneled walls - these and a multitude of like offenses against harmonious tone relationships are constantly to be met with.