Dyers'-Weed, or Yellow-weed, Resoda luteola, L. an indigenous annual plant, growing in meadows, pastures, on walls, and barren uncultivated spots, particularly on the rubbish thrown out of coal-pits. It has a cylindrical, hollow, furrowed stem, and produces yellow flowers, which blow in the month of June or July. This plant is not relished by cattle, few eating it, except sheep, which sometimes browse it a little.
The dyers'-weed imparts a most beautiful yellow colour to wool, cotton, mohair, silk, and linen, and is principally used by dyers for that purpose, as it affords the brightest dye. A deco6tion of this plant also communicates a green colour to blue cloths, and constitutes the basis of Dutch pink. The tinging properties reside in the stems and roots, which should be cultivated in sandy situations; because rich soils render the stalks hollow, which consequently do not impart so delicate a colouring matter. As the durability and brightness of the colours obtained from this plant greatly depend on the circumstance, whether a just proportion of alum and cream of tartar have been used for the lye, in preparing the goods before they are dyed, we can from experience re-commend three parts of alum to be used to one of tartar : if more of the former be employed, the colour will be pale ; if a greater quantity of the latter, it will acquire an orange-shade. - M. Gadd informs us, in the 20th vol. of the Transac-tions of the Swedish Academy, that he found the following proportion of ingredients to be the most practically successful in making the preparatory lixivium : viz. for one pound of wool, two ounces of alum, six drams of cream of tartar, to be dissolved in three gallons of water, to which are to be added two hand-fuls of whenten bran. After remaining twelve hours in this decoction, the wool is to be taken out, rinsed, then half-dried, and afterwards boiled together with one pound of dyer's green-weed, in four gallons of water ; and after it has been some time over the lire, the plants should be removed, and half an ounce of the purest pot-ash (which must contain no lime, like the Essex ashes) added to the liquor ; when the wool must be gently agitated, till it acquire the proper shade of yellow.' The colour maybe heightened by an additional portion of pearl-ashes, or salt of tartar ; but its durability will thus be affected. - If silk or linen are to be dyed, both the tartar and bran must be omitted, and the-colouring matter fixed with alum and potash : but, in woollen cloth or yarn, the permanency of the colour is remarkably promoted by the addition of wheaten bran.