Colors of Calico - Chemical Questions.

Scientific American 9, 15.10.1853

A correspondent propounds the following questions. First, "what is the reason that blue figures on the muslin prints of ladies's dresses, will, when exposed to the sun, lose their color, which will be restored again when the goods are hung up in the shade? Second, is there anything known which can be put into the water in washing calico, or other dresses, which will make the goods retain their colors? - Such knowledge would be a great blessing to every mother and housewife."

These are very plain and apparently very simple questions, and as many think that those who are acquainted with the sciences, shoud be able to solve any question in science; it may be expected that we should be able to answer the above, to explain the phenomenon described in the first question, and tell how to fulfill the desires expressed in the second. No man can give a direct answer to the first question, and we cannot gove an affirmative answer to the second. To more knowledge we acquire, the more fully are we impressed with a sense of man's ignorance of causes in the physical world. If any person were to ask of us, "what is color?" we would have to answer, "it is something, nothing." We are cheered with the prismatic glories of the lovely bow which arches the heavens above us; we are delighted with the gues of the rose, the violet, the dahlia, the tulip, and the modest daisy; we drink in pleasure by feasting our eyes on the foliage of the forest, the dancing butterfly with his variagated beauties, the humming bird on azure wing, and the purple and golden clouds which mantle the western sky. And yet these delights and pleasures are derived from that which has no material existence in itself. Color is a quality with which the Great Author of Nature has endowed matter, to give his creatures pleasure, and to enable them to distinguish between different objects; it may be called the chemical quality, as form is the mechanical quality, to distinguish objects.

The blue on the goods referred to by our correspondent, is one with which we are not acquainted; we have seen indigo, copper, logwood, and prussian blues exposed to the sun and never saw the colors destroyed by such exposure, and again restored by transferring them to the shade. These are various kinds of blues, both printed and dyed; that is, they are produced by different substances, such as indigo, copper, prussiate of potash, and logwood. The sun affects every color on goods; it bleaches turmeric and annatto yellows in a very short time, but indigo blue is what is called a fast color. These colors which are called "fugitive," cannot resist the action of soap and hot water, and sun exposure; those named "permanent" can stand both of these tests. Colors on goods are formed by substances which adhere with great mechanical tenacity to the goods on which they are printed, and reflect the different rays and sub-rays of light. There are only three primative colors, namely, red, blue, and yellow; these mingled in different proportions, form all the tints and hues which adorn Flora's mantle. We do not know why it is that the sun light affects colors in the manner it does, we only know by experience that it does so. It would have been as puzzling for us to answer a more radical question than the first one propounded; namely "why is it that there is such a color as blue," or why is it that two yellow substances, when combined together, will produce a salt which will reflect the blue ray of light - a blue color - or why two other yellow substances when combined together, will produce a black solution. A solution of the oxyde of iron and the prussiate of potash will produce a blue; a solution of the oxyde of iron and sumac will produce a black solution. The action of the rays of light - actinism- as it is now named, in relation to color, is something respecting whic but little is known, excepting such experience as that of our dyers, calico printing chemists, and photographers.

There is no substance which can be put into water suring the washing of calicoes or dresses to precent the coor from fading, but we will give some directions for washing of delicate colors, in muslin or other textile fabrics, which we have no doubt will be a benefit to many. Never wash goods having delivate colors in warm suds; nor rub bar soap on them at any time. - Dissolve some soap so as to have strong suds, and set it aside until it is quite cold; wash the goods in this, and when the firt is all removed wring out and rinse well in clean cold water; be sure and not have the suds too weak, or the soap will be decomposed and stick in the goods like hard tallow. After wringing, finish out the dress or goods in a vessel containing some alum dissolved in clean water, or some alum water stirred among the starch. Wring out well and dry in the shade. Strong bran water - bran boiled in water and left to cool - is very excellent for washing delicate muslin dresses. Some use ox gall for washing fine woolen goods, but cold strong soap suds are better. Be sure and rinse the soaped goods or dress clean in soft water, and squeeze well, so as to take all the soap out. Soap has a tendency to blue red colors, and to fade the blue in green colors; alum restores the color; in other words, so combines with the substances in the calico, to reflect the green, which is a mixture of the blue and yellow rays and also the red ray, which is a primitive color.

Every single color can be produced by many different substances, some of which make fast and some fugitive colors, and it requires a great knowledge of practical chemistry, to tell what color is fast, and what is not, on a piece of goods. The application of chemistry to the arts of coloring textile fabrics, encircles the largest area of practical chemistry, and yet the teachers of chemistry in out colleges, are in general very ill-informed about it.

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