This is to be made the same as for green; it need not be neutralized as for cotton. For _blue_, however, _twelve_ ounces of indigo are necessary to four pounds of sulphuric acid. In dyeing the heat must be much under boiling, or the using of a high heat would give the blue a green tinge. This blue colour is very bright, yet not fast, but no preparation is of any advantage to either its fastness or brightness. Some put alum and tartar, and some use one, and some the other, to prevent a green cast: if, however, the wool be fine, white, and worked _much below_ the boiling point of heat, it will not turn green although neither be used. _To dye wool_ ORANGE, GOLD COLOUR, _&c._ The processes of crimson, scarlet, and of yellow united produce the various shades of these colours, _leaving archil out_. See _buff, peach, &c. on wool_. _To dye wool_ BLACK. Black includes a prodigious number of shades, beginning from the lightest grey or pearl colour to the most intense shade of black. On account of these shades it is classed by dyers among their chief or primitive colours[8]; for the greater number of browns, of whatsoever shade they be, are finished in the same dye as would dye white wool a grey more or less dark. This operation is called _browning_. The best superfine black should have a full ground of _mazarine blue_ previously to being finished black. A great quantity of cloth and other articles have, however, no indigo ground, but a ground of logwood, or of logwood and alder-bark, or of logwood and old fustic, or of logwood, alder-bark, and old fustic, all boiled together, and sometimes they are boiled in a decoction of oak saw-dust. Indigo for the ground is the richest drug, in carbon, that is or can be used; logwood is next to it: too much logwood, however, whether indigo be used with it or not, gives the black a foxy hue; alder-bark and old fustic modify this effect, and are used in small quantities for this purpose, because the dye from these, as well as that from oak saw-dust, will produce a soot or dead black. A _jet_ black is required full and rich, therefore old fustic and oak saw-dust are only used to modify the richness of the ground as it regards the blue, whether of indigo or of logwood; for logwood especially, without these, if overcome with sumach and sulphate of iron only, would be foxy, purplish, or have a reddish cast. So many different grounds being used for blacks, and every dyer thinking his own the best, is the occasion of such a great variety of hues, even of black, being found in the market. It is, therefore, thought unnecessary to describe the various methods of dyeing black which are pursued by different dyers, and which would be, in fact, impossible. But the author has done what is of much greater importance to the student, who, after a little practice, let him have a pattern of black to dye, will know how to do it, let who may have dyed it.