LIGHT BLUE.
I. To dye this delicate color well, special care must be taken in cleaning the feathers, for which purpose only olive-oil soap of the best quality, with a little ammonia, ought to be employed. When they are perfectly clean and no more grease upon the stems, rinse them first in one or two lukewarm waters, then in cold water until the last trace of soap is removed. Then fill your basin or dyeing pan three-quarters full of cold water; put in, for a dozen feathers, one hundred and eighty grammes (about eight ounces) of raw starch in a sufficient quantity of good indigo extract to give the starch-bath the desired shade. Enter the feathers and work them gently until they are completely dyed, that is, for about fifteen or twenty minutes. Then take them out, squeeze out the starch by putting them between the fingers and thumb of your hand, and shake them before the stove, or in a well-warmed chamber until dry. While drying, beat them from time to time upon the board, or between the hands to remove the adhering starch.
II. Prepare a lukewarm bath acidulated with a few drops of sulphuric acid, so as to give a faint sour taste, to which add, according to shade, solution of methyl blue B. (Actien Gesellschaft fuer Anilin Fabrikation, Berlin). Enter the feathers and leave them in the bath until cold, or until uniformly dyed.
Note.—Some dyers use alkaline blue, which is not, however, recommendable, because alkaline baths, as above remarked, are injurious to the feathers and must be avoided as much as possible.
III. Prepare bath of lukewarm water, dissolve in it about one-half ounce tartaric acid per one quart, and add one ounce indigo carmine per quart of liquid; stir well, enter the feathers and agitate or lay down in the bath until the required shade is obtained. This color shows little fastness to light and air, which can be improved, however, by adding to the dye bath one-quarter ounce alum per quart. The shade being obtained, take up the feathers and pass, without rinsing, through raw starch milk, dry and beat as described.
Light blues, as is easy to understand, can only be dyed upon white feathers for the most delicate shades; nearly white, or developed gray feathers may be used for the shades approaching a light medium blue.