To produce shades having more of a gold colour, anotta is added in propor tion to the depth of the colour required.
Lighter shades, such as pile lemon co lour, are obtained by previously whiten ing the silk, and regulating the propor tion of the ingredients of the bath by the Sbade required. To gilie a yellow, with . , a green tinge, a little indigo is added' to the bath, if the silk has -not been previ= ously azilred ; to prevent the greenish shade being too deep, the silk should be. more slightly alumed than usual.
Br. Bancroft asserts that all the shades of yellow can be given at a cheaper rate' by quercitron bark than by weld. TO dye with this bark, a quantity of it pow dered, and inclosed in a bag, in propor. tion to the shade wanted, from one -to two pounds for every pound of sill; is into nto the vat while the water' is cold. Heat is applied, and when the bath is ra ttier more than blood warm, or of the temperature 100°, the silk, after being first aIumed, is immersed and dyed in the usual way. A deeper shade may be given by adding a small quantity of chalk or pearl-ashes towards the end of the opera tion. To prOduce a more lively yellow, a small portion of murio-sulphate of tin may be employed, but it should be used cautiously, as it is apt to diminish the lus.; tre of the silk.
To dye silk of an aurora or orange co lour, after having been properly scoured, it may be immersed in an alkaline solu tion of anotta, the strength of which ig to be regulated by the shade required. The temperature of the bath should be between that of tepid and boiling water. When the desired shade is obtained, the silk is to be twice washed and beetled, to free it from the superfluous colour ing matter, which would injure the beauty of the colour. When raw silk is to be dyed, that which is haturally white should be selected, and the bath should be near ly cold ; for otherwise the alkali, by dis solving the gum of the silk, destroys its elasticity. Silk is died of an orange co lour by anotta, but if a redder shade be wanted, it is procured by alum, vinegar, or lemon juice. These colours are tiful, but do not possess permanency., Of dyeing Cotton and Linen yellow.
In dyeing cotton or linen yelloW, the first operation is to scour the stuff with a ley prepared from the ashes of green Wood ; it is then washed, dried, and alum ed with one fourth of its weight of alum after twenty-four hours, it is taken out of the alum liquor, and dried without being washed. A weld bath is then prepared, by an infusion of a pound and a qtiarter of weld for every pound of the stuff, and in this it is dyed, by being turned and wrought till it has acquired the proper shade. It is then taken Out of the bath,
and soaked, for an hour and a half, in'a solution of a quantity of sulphate of cop per equal to one fourth of the weight of the stuff; it is then thrown, without' being washed, into a solution of soap, in the same proportions : after being well stirred, it is boiled in it, for near ly an hour, and then well washed and dried.
If a deeper colour is wanted, the stuff is not aimed, but two pounds and a half of weld are used for every pound of the stuff, for each of which a drachm of ver digrise mixed with a part of the bath is added ; in this bath it is dipped and work ed, till it has acquired an uniform colour ; it is then taken out of the bath, and a lit tle ley of soda poured in ; after this it is again returned into the bath, kept there a quarter of an hour, and then taken out, wrung, and dried. Other shades of yel low may be obtained, by varying the proportion of the ingredients ; a lemon colour may be procured, by using only one pound of weld for every pound of cotton, and by diminishing the propor tion of verdigris, or using alum as a sub stitute.
" Dr. Bancroft directs a method for dye ing cotton yellow, which he asserts to be much cheaper, and which appears better in several respects, particularly as to the mordant. It is as follows : The mordant to he used is the acetite of alumen, formed by dissolving one pound of sugar of lead, and three pounds of alum, in a sufficient quantity of warm water. In this liquor, heated to 100°, the cotton is to be steeped two hours,after be ing first properly rinsed. It is then taken out and moderately pressed over a ves sel, to prevent waste of the liquor. It is then dried in a stove heat, and after being again soaked in the aluminous solution, is wrung out a second time and dried : it is then barely wetted with lime-water, and afterwards dried ; and if a full and bright colour is wanted, it may be neces sary to soak the stuff again in the diluted aluminous mordant, and, after drying, to wet it a second time with lime-water : after it has been soaked for the last time it should be well rinced in clean water, to separate the uncombined portion of the mordart, which might injure the applica tion of the colouring matter. By the use of the lime-water, a greater proportion of alumen combines with the stuff; as well as a certain portion of lime.