DYEING WITH WELD.

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produced. With chromium mordants an olive-yellow is produced. These shadesare the same upon cotton, silk, and wool, but vary slightly within narrowlimits. In dyeing there are employed — (1) the raw vegetable material as itoccurs in commerce, generally in the state of a more or less finely pulverisedsubstance ; (2) the same material after having been previously treated withdilute and boiling sulphuric acid, the produdt of this adtion yields richer andbrighter colours, but requires in dyeing a higher temperature, and as a con-sequence thereof the portions of the fabric intended to be left white are moresoiled. When the dye material contains tannin in larger quantity, as is thecase with quercitron, fustic, and others, it is best to add to the materials ofthe dye-beck a sufficient quantity of gelatin, in order to neutralise the effedtsof the tannin.

Calico is now very generally dyed yellow with quercitron or quercetin, butformerly weld was used, and with the advantage that it yielded faster colours.As regards cotton or calico, previously printed and mordanted, and treatedas described for madder, the pieces, four at a time, are placed in a dye-beck,containing per piece, from 750 to 1500 grms. of quercitron, and 60 grms. ofglue to each 500 grms. of the last-named substance. The colouring matterdissolves so readily that the goods can be put in the beck immediately afterthe addition of the^ dye-ware. The process is commenced at the ordinarytemperature of the air; the heat of the contents of the dye-beck is raised inan hour’s time to from 38“ to about 57 0 , but for greys the temperature shouldnot exceed 38°. On being taken from the dye-beck the pieces are firstthoroughly washed and rinsed in cold water, and next put for a quarter of anhour in a bath of bran, containing 2J kilos, of bran per piece, and at a tem-perature of from 38° to 51°. If the patterns have much white this operationhas to be repeated twice, the objedt being to clear and brighten the grounds.This branning is the only clearing which this dye-ware will bear.

Dyeing with Weld.—The plant is first boiled in the dye-beck for abouthalf an hour; it is then removed, and the contents of the beck allowed to cooldown to about 63°; at this heat the goods are entered, four or six pieces at atime. The quantity of weld applied varies from 5 to 10 kilos, per piece,according as the pattern printed on the fabric is more or less heavy; whena white ground is required, and the pattern is light, it is as well to add about60 grms. of glue for each half kilo, of weld. The temperature of the dye-beck is raised in half an hour’s time to 75 0 ; on being removed from the beckthe goods are twice branned, the quantity of bran to be 5 kilos, per piece forwhite ground, and 2J kilos, per piece for yellow ground. After this the piecesare grass bleached for a few days, and next passed through dry bran. Theuse of weld (although discontinued in this country) has the advantage ofleaving the whites purer and more readily cleared than is the case with quer-citron. Pomegranate bark is employed like weld, that is to say, boiled in thebeck previous to use.

Fast cinnamon-yellow or brown shades in the madder style are often firstdyed with quercitron and bablah,*or quercitron and pomegranate bark. Where

* This is the name (also babula or Neb-nab) of a fruit imported from Senegal and India;it was, when first imported, said to have the property of imparting permanency to all dyedcolours, but this was found to be an exaggeration. Bablah contains tannic and gallic acidsin large quantity, and may be used as a substitute for sumach.