WELD, OK DYER'S WEED. 



515 



equal quantity of similar colouring matter. 

 This is one of tlie strongest grounds for prefer- 

 ence that has been brought forward Iiy Dr Ban- 

 croft in favour of that bark. 



The beauty of the weld colour, however, not- 

 withstanding the great bulk of the article, as 

 compared with other dyes, causes it to be much 

 used by dyers, calico-printers, colour-makers, 

 and paper-hanging manufacturers. It is an adjec- 

 tive colour, but tolerably permanent when used 

 with alum and tartar as a mordant. 



In the year 1773, the sum of two thousand 

 pounds was granted by act of parliament to a 

 Dr Williams, as a reward for his discovery of a 

 fast green and yellow dye on cotton yarn and 

 thread. Tliis supposed fast colour was given by 

 the combination of weld with a certain mordant, 

 the composition of which the patentee was per- 

 mitted to conceal, that foreigners might not 

 enjoy the benefit of his discovery; while he, on 

 his part, engaged to supply the cotton and thread 

 dyers with his dye at a certain fixed price. The 

 mordant used was supposed by chemists to be a 

 solution of tin alone, or of tin and bismuth, 

 which gives to weld yellow the power of resist- 

 ing the action of acids and of boiling soap-suds, 

 though it is not proof against the continued 

 action of the sun and air. This defect, however, 

 was not easily discoverable, in consequence of 

 the ingenious method which, according to Dr 

 Bancroft, the inventor employed to obtain a 

 fiivourable testimony of the dyers on the subject. 

 He caused his specimens of dyed yarn to be 

 woven into pocket-handkerchiefs, and gave them 

 to 1)6 worn in the pockets of those who were 

 afterwards to attest to the goodness of his dye; 

 and as handkerchiefs enclosed in pockets are not 

 exposed to the sun and air, this want of per- 

 manency of colour was not discovered until some 

 time after the reward had been paid, for an in- 

 vention which proved of little or no value. 



A water-colour, called weld yellow, is much 

 used in paper-hanging manufactories. This 

 pigment, as it is usually prepared in London for 

 sale, is the extract of the plant, and is in the 

 form of hard lumps, which must be ground into 

 powder previously' to being used. Every colour 

 is in some degree injured by that operation. 

 Messrs. Collard and Fraser, therefore, use a pro- 

 cess by which the necessity for subsequent 

 gi-inding is avoided, the colour being obtained 

 in the form of a fine powder. To produce this 

 desirable result equal quantities in weight of 

 carbonate of lime and soft water are put into a 

 copper vessel ; the mixture is raised to the boil- 

 ing point, and stirred until it becomes of a uni- 

 form consistence. Then, to each pound of car- 

 bonate of lime, three ounces of pulverized alum 

 are added; this is gradually mixed in, and as 

 carbonic acid gas is by this means disengaged, 

 the operation must be carefully peifoi-med, lest 



the effervescence which takes place should cause 

 the mixture to overflow from the boiler. When 

 the effervescence has subsided, this part of the 

 process is completed, the fire is withdrawn, and 

 the mixture may remain any length of time 

 without injury. Meanwhile the weld plants are 

 placed with their roots uppermost in another 

 copper vessel, into which soft water is poured in 

 just sufficient quantity to cover every part con- 

 taining seed. These plants, after being boiled 

 for a quarter of an hour, are removed to a tub, 

 where they remain until the liquor is drained 

 from them; the water in which they have been 

 boiled, added to these drainings, are then passed 

 through a flannel filter, to intercept the seeds 

 and fecula. The quantity of plants required 

 for a given quantity of carbonate of lime cannot 

 possibly be ascertained with accuracy, for some 

 bundles contain three times as much colouring 

 matter as others; but should too much of either 

 mixture have been prepared, it can be kept in 

 earthen vessels for many weeks without being 

 in any way deteriorated. 



When the weld liquor has been thus prepared, 

 a fire is again kindled under the boiler con- 

 taining the basis to which the weld liquor is 

 added. The proper degree of colour required 

 can only be obtained by trial. When the mix- 

 ture is found to have a due proportion of each, 

 it is raised to a boiling heat, and the process is 

 completed. The contents of the vessel are tlien 

 put into an earthen receptacle, and the colour 

 precipitates in the form of a powder. The next 

 day the supernatant liquor is drawn off, and the 

 residuum placed on largo pieces of chalk, which 

 in a few hours absorb the moisture, leaving the 

 colour dry and fit for use. The liquor poured 

 off from the colour is, with the addition of 

 water, used again; the old plants are likewise 

 boiled a second time previously to the addition 

 of fresh ones, so that no colouring matter is lost. 

 Iron vessels must not on any account be used 

 in this process; for the gallic acid, which is 

 very abundant in weld, would instantly dis- 

 solve the iron, and "the smallest particle of that 

 metal is fatal to the delicacy of the weld yellow. 



Although cultivated in the parts of England 

 we have mentioned, a sufiicient quantity of weld 

 is not produced for our home consumption, and 

 we consequently draw it from foreign markets. 

 Some writers have recommended the extension 

 of its cultivation, and argued that it would 

 thrive and render a handsome profit on some of 

 our poorest lands, which for any other purpose 

 are not worth ten shillings per acre. Marshal, 

 in his Rural Economy of Norfolk, says, it prefers 

 a good soil, but others assert that it becomes 

 stalky in a rich soil; and the author of the 

 Journal of a Naturalist, supports the opinion 

 that very poor land is the best for the purpose. 

 "With us," he says, "it grows luxuriant!}'- («. c. 



