Scientific American 3, 16.7.1868
It is ofter worth while to think upon and discuss those things which are apparently of small importance. The laws of nature apply to small as well as to large operations, and the explanation of phenomenon of great importance may frequently be found in the investigation of trifling occurences.
Mr. Ruskin, should this meet his eye, would no doubt smile, while he would acknowledge the truth of the statement, that the same natural principled, by the observance of which the great Turner (who he asserts was the only artist who ever did paint water true to nature), obtained his effects, include the one by which a washerwoman makes a bosom assume a whiteness of snowy purity.
All tints are hightened by transmitted light. No artificial pigments or dyes whatever can approach the glory of the prismatic colors; but if artificial colors are laid upon a transparent surface, and light will at once be seen. The stained windows of churches are good illustrations of the increased beauty of color by the transmission of light.
The effect of transparency may however be produced in some degree by artificial means. Light in passing through transparent substances is more or less separated into its primary colors by differences in thickness and density, and the form of the surface. Moreover the color of the transparent body itself has effect in the absorption of other colors, so that light rarely passes through transparent bodies unchanged. It took a long time to discover a means by which the dispersion of light, when it passes through the lenses of optical instruments, could be obviated, so that the image presented to the eye should exhibit the colors of the object inspected by the aid. It is obvious then that if a tint be added to a color so delicately that the impression produced by it does not change the original tint essentially, something of the effect produced by the transmission of light will be attained. The less of admixture with other colors any tint possesses, the more easily will light be transmitted through it; or perhaps it would be proper to say, that unless the mixture be so perfectly compounded that a distinct new tint is produced without a muddy crude appearance, the transmission of light will be more or less interfered with. This perfect blending is what is called by artists purity of tint. It is seen in perfection everywhere in nature, in the clouds, in water, in flowers, leaves, and fruit. An absolute white has a dead, dreary appearance, caused by the utter absence of the effect of transparency. It is, therefore, rarely used in ornamental work unless it be so placed as to be enriched by delicate reflections from adhacent objects. What is generally called a pure white has more or less of a very delicate yellow, green, or blue tint, the absemce of which would be very sensibly felt, although its presence, as a tint, is scarcely perceived. This is why blueing is used in the starching of linen, though we venture to say, that the reason for it has rarely been thought of sufficient importance to repay analysis.