Home › Bleaching And Scouring › Preliminary Remarks (Art of dyeing has)

Preliminary Remarks (Art of dyeing has)

The art of dyeing has for its object the fixing permanently of a color of a definite shade upon stuffs. The stuffs are animal, as silk, wool, and feathers, or vegetable, as cotton and linen. The former take the colors much more readily, and they are more brilliant.

In some cases, as in dyeing silk and wool with coal-tar colors, the color at once unites with the fiber; generally, however, a process of preparation is necessary. In certain other cases, as in dyeing silk and wool yellow by nitric acid, the color is due to a change in the stuff, and is not properly dyeing.

Insoluble colors are managed by taking advantage of known chemical changes; thus chromate of lead (chrome yellow) is precipitated by dipping the stuff into solutions, first of acetate of lead, and then of bichromate of potassa.

Mordants (bindermittle, middle binder of the Germans) are bodies which, by their attraction for organic matter, adhere to the fibre of the stuff, and also to the coloring matter. They are applied first; but in domestic dyeing they are often mixed with the dye-stuff. By the use of a mordant, a dye which would wash out is rendered permanent.

Some mordants modify the color; thus alum brightens madder, giving a light-red, while iron darkens it, giving a purple.