The discovery of the so-called aniline dyes has greatly increased the variety of colors available. Although some of the first aniline dyes to be made were not fast to washing or to light and they thus received a bad reputation, they are now to be obtained which compare favorably in fastness with the natural dye stuffs such as cochineal, madder, etc., provided sufficient time and care are given to dyeing. The chief trouble is that in the endeavor to furnish cheap goods, processes are hurried and results are unsatisfactory.
Home dyeing is practically confined to the use of direct aniline colors. These are put up in small quantities and sold in many places. Directions for their use are given on the packages. The chief precautions are to have the goods perfectly clean and thoroughly wet before entering into the dye bath (this is by no means as easy as one might think), and to keep the goods in motion while dyeing so as to prevent unevenness of shade. Wool and silk dyes cannot be used for cotton and linen, nor the reverse. Of course cloth already colored cannot be dyed a lighter shade of the same color and the original shade must be very light to enable one to change the color, say from red to blue, etc. The original color always modifies that of the dye somewhat and it is best to experiment first with a small portion of the dye and cloth. Rather dark shades are apt to be most successful.
Indigo for blue, madder for Turkey red, logwood with fustic for black, cutch or gambia for browns on cotton are about all the natural dyestuffs which are used to any extent commercially at the present time. The artificial product alizerin, the active principle of madder, has about superseded the natural dyestuff, and artificial indigo is gaining on the natural product.
Linen is bleached and dyed in much the same manner as cotton, although the process is more difficult. The process of bleaching weakens linen more than cotton.
Woolen and silk may be dyed directly with a great variety of dyes without the addition of a mordant, although they are often mordanted. Both must be well washed or scoured before dyeing. When white or delicate shades on woolen or silk are desired they are bleached. The bleaching is usually done with sulphurous acid gas, the cloth or yarn being exposed in a damp condition to the fumes of burning sulphur.