The Art of Dyeing No. 7. Blue on Cotton.

Scientific American 21, 10.2.1855

In the last article we described the method of dyeing indigo blue on cotton by the cold vat. Blue color can be dyed by various plans and with different substances.

Indigo Logwood Blue

The old-fashioned logwood blue is dyed by giving cotton a bottom of indigo and topping with logwood. A middling deep shade of indigo is first dyed on the cotton by either three or four dips in the blue vat, then the goods receive a weak sour (vitriol nod water,) are washed, run through a tub of pyroligneous acid (mordaunt) then squeezed or wrung, then run through a tub of warm water, and wrung or squeezed for the logwood. The quantity of logwood given depends on the depth of shade desired. About three pounds of logwood for every ten pounds of cotton, makes a heavy topping. The color has a deep coppery blue appearance, like a very rich indigo color, but the logwood being fugitive it soon fades. The goods are generally raised with alum — for an alternate — in the logwood, after receiving five turns in the logwood liquor; with three more turns they are fit to be lifted out, washed, squeezed, or wrung, and dried.

Logwood Copper Blue

Take the liquor of five pounds of logwood well boiled, and two ounces of the sulphate of copper dissolved, and put them into a tub for ten pounds of cotton. Enter the goods and handle well by turning for fifteen minutes. Lift them out then, and enter them into a tub of clean cold water, into which a quart of urine has been stirred, and then handle the goods in this for fifteen minutes, take out, wash, squeeze or wring, and dry. This is a very fugitive color, but it will answer very well for carpet rags.

Copper Blue

This color is dyed on cotton, by repeated dips, in a strong solution of the sulphate of copper, then in a vat of caustic ley. It takes about three pounds of the sulphate of copper to make a moderate deep blue — sea blue — it is a tedious color to dye; it stands washing well, and is of a peculiar tone — very chaste for gingham summer patterns.

China Blue

This is a light blue shade, and is given to cotton by neutralizing the sulphate of indigo with the acetate of lead. It will not stand the action of an alkali, but is a very clear toned color. Some neutralize the sulphate of indigo from chalk, but the sugar of lead is better, though dearer. This makes a very fine paste blue when thickened with gum, for calico printing.

The sulphate of indigo is made by feeding gradually ground indigo — the best quality only should be used — into pure sulphuric acid, and stirring up until all the indigo is dissolved. Five pounds of vitriol requires one pound of indigo, which is ground in a mortar, and sifted through a fine brass wire sieve.

Royal Blue

This color until within a few years, although well known, was seldom dyed on cotton, because it was so expensive and difficult to make it dark. For many years it was known by the name of "Prussian b[l]ue." It is dyed with the nitrate of iron, logwood, salts of tin, and the prussiate of potash.

Take three tubs and make the first up with a strong solution of the nitrate of iron, (prepared by dissolving clean iron hoops slowly in aquafortis) about 5° in a Twad. hydrometer, and handle the cotton in this for fifteen minutes; then lift, and squeeze or wring. Enter again into a tub of logwood liquor very strong, into which has been added a solution of the crystals of tin, handle in this for ten minutes, then lift, wring or squeeze. Enter again into a clean tub containing a solution of the prussiate of potash, and handle in this for ten minutes, then lift and add some of the muriate of tin, and the oil of vitriol, enough to change the liquor from a bitter to a slightly sour taste, enter the cotton and give five turns, then lift up, wash well, and wring or squeeze for drying. This process makes a deep rich blue color, and is nearly as permanent as an indigo blue. For ten pounds of cotton it takes four pounds of logwood, one of the crystals of tin, and one of the prussiate of potash. Light shades of blue can be made by using less dye stuffs, and a weaker solution of the nitrate of iron; and for very light blues no logwood or crystals of tin are used, simply the two tube — the nitrate of iron, and the prussiate of potash. For very light blues, the cotton must be bleached. Some use the crystals of tin in the iron liquor for light blues; it is best when this is done, if logwood is used, always to give some muriate of tin for raising along with the vitriol, in the prussiate of potash tub, as has been described, for the deep blue.

Royal Blue on Silk.

This is dyed in the same manner exactly as on cotton. It will always be understood that the cotton and silk have been prepared by cleaning, to receive the dye, as was described in article 1. China blue is dyed on silk with the sulphate of indigo, but it is a very fugitive color, it can be washed out with warm water, and even rain washes it off.

Fast Blue

A very fast blue can be dyed on silk, by giving a bottoming of archil, then topping off in a woad vat, or a clear sharp, strong, indigo vat, used for dyeing cotton.

Very little logwood must be used in dyeing silk with iron and prussiate of potash.

Dyeing woolens blue in our next.