This same property, however, of combining directly with the fibre, makes the colors brighter and more brilliant than many of the other classes, especially in the lighter shades. Accordingly for bright, pretty shades of pinks, blues, yellows, and of mixed shades, fast to light, but not very fast to washing, very easily and simply applied, these colors are extremely valuable. For instance, in dyeing large quantities of bright colors on calico or cheesecloth, for some special occasion, as a pageant or spectacle, these are the colors to use. Another great advantage they possess is that they dye true; that is, they do not alter their color when exposed to the air, and the color of the finished goods can be fairly estimated from the color of the dye-bath. Accordingly, the student is strongly urged to practise the art of dyeing with these colors. They are cheap and can be readily obtained, although not always of the very best quality, under the name of Diamond Dyes for cotton, ezy dyes, etc., from druggists and grocerymen all over the country. They can be easily applied to cheesecloth, muslin, and other inexpensive materials, and if care is taken to soak and boil the goods thoroughly, to linens and heavy cottons. In case of necessity they can be used on wool and silk, but, as a rule, their use is limited to vegetable fibres. They are particularly valuable to amateur dyers and to beginners in the art, because they have great “levelling” power; that is, it is easy to dye evenly with them. On the other hand, it is a nuisance, oftentimes, to have to boil the goods, and even then the colors are not really fast to washing. At any rate, before proceeding to the study of the more permanent but more complicated Sulphur and Vat colors, the art of dyeing even and rainbow shades and at least the beginnings of the art of combining and matching shades should be carefully and conscientiously worked out with these often despised, but really very useful and valuable, Salt colors. CHAPTER IV THEORY AND PRACTICE OF COLOR DYEING Directly the student has mastered the instruction contained in the three previous chapters, and can use the dyeing apparatus and the unmixed dyestuffs so as to get reasonably fast colors on cotton and linen goods, it is time to attack the more difficult subject of dyeing to shade. This art is not an easy one, by any means, and only a few fundamental principles can be learned from a book. To make any real progress in it, constant and continuous practice is necessary; even then, unless the student is naturally gifted with an eye capable of readily detecting any changes of color, and has trained it to distinguish and identify the causes of such changes, little success in the matching of colors can be hoped for.