Metallic Oxides
Metallic oxides are used to stain or color clear glazes, while underglaze colors are ordinarily used for matts. The percentage of stains to be added to the dry glazes is stated in [Figure 464] where they can be readily traced to their approximate locations in the hue rectangles by the reference letters M1, C1, etc. Certain oxides are weak coloring agents and require larger amounts of oxide to color the glaze perceptibly.
Iron and copper oxide may be mixed to produce a large variety of yellow greens; other combinations will suggest themselves. It is possible to use oxides as well as underglaze colors for staining matt glazes.
Harmony of Color
We have, to this point, considered the enrichment of large surfaces whose areas were arbitrarily determined by construction, as, for example, the extent of wall surface, ceiling, or wood trim and furniture. The essential element in this type of problem is the selection of a one, two, or three-hued color arrangement that would harmoniously link ceiling, wall, and wood together. If we had introduced stencilling or figured wall paper it would have immediately called for the solution of another problem, the factor of how much strong color to use. In other words, it would have introduced the question of proportionate distribution of color upon a given area. It was thought best to limit the subject of proportionate distribution to small areas, where the designer is often forced to make decisions and to divide surfaces into proportionate color parts for his surface enrichment.
We may now repeat the definition of harmony with the accentuation placed upon a certain wording directly applicable to small surfaces. Harmony is obtained by the proper balancing and proportionate distribution of value, hue, and chroma upon a surface to give a unified and pleasing reaction to the eye and intellect.
Proportionate Distribution of Color for Small Areas
Rule 12k. Proportionate distribution of hue, value, and chroma in surface enrichment calls for a small area, high in chroma, and contrasting in value to the rest of the surface but harmonizing with it. This is usually located in the area of concentration. The larger areas are to be sufficiently reduced in chroma and value to form a slight contrast with the background.
Examples of Proportionate Distribution
[Figure 465] illustrates some of the salient factors of distribution of values and hues. Hues of or near standard chromatic intensity should be used in small quantities and should accentuate the point of concentration. These small areas are to be regarded as giving brilliancy and life to the surface and to hold the eye at the point of concentration. Very small surfaces are capable of sustaining spots of high chroma, as is shown in the silver pin of [Figure 468]. The remaining portions of the surface enrichment should be kept subordinated in hue and value to the point of concentration, but related to it. The bands of [Figure 465] are well reduced in value and make little contrast with the background, thus forming true surface enrichment or that which neither rises above or apparently falls through the surface. The point of concentration is higher in chroma than the surrounding areas.