ACCESSORY OPERATIONS.

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—after being repeatedly sulphured (see p. 88) and washed in the usual manner,the fabric receives a final washing in the decodtion of Panama bark, whichleaves it more lustrous to the eye, and softer and more kindly to the touchthan the best-balanced and most emollient soap. Some good practicalauthorities maintain that where quality is of more importance than cheapnessthe process of sulphuring should be performed,—not with the fumes of burningsulphur, but with a solution of the bisulphite of soda (leucogene), or, betterstill, bisulphite of magnesia. As to the mordanting power ascribed to thesebisulphites, further experiments are wanting.

Returning to the prevention of irregularity in piece-dyeing, in case ofcolours whose affinity for the fibre is very strong, it is often found prudent todissolve at the outset merely a part of the dye needed to bring up the goodsto the shade required, and to add the rest by degrees. A good mechanicalprecaution to ensure a level shade is to wince the pieces at first with greatswiftness. The wetting the pieces with water previous to dyeing is also apoint of importance. If any portions of the goods have escaped being tho-roughly moistened, or if they are in the least degree greasy, soiled, or abraded,irregularity is certain.

Another essential point in piece-dyeing is thorough penetration of thecolour, so that, if a small portion be torn or cut off, the sedtion or tear maybring to light no undyed filaments. If the cloth is not dyed through andthrough it will, after a little wear, begin to exhibit a greyish reflection, andcomplaints will reach the dyer that his colours “ wear off.” Cloth that is notdyed through generally displays a correlative fault; the colour is depositedloosely on the outside,—“ plastered on,” as it is technically called, and ishence deficient in lustre.

Rag-dyeing is a branch requiring more skill and judgment than the outsidepublic are aware. Woollen clippings and rags, after some rough sorting asregards colour, are re-dyed preparatory to being converted into shoddy and re-manufadtured. As these rags have been dyed before, the production of thenew shade required is attended by the discharge or alteration of the old.From the nature of the case it is important that these changes should beeffected with the smallest possible outlay in wares. To take a very simplecase—the conversion of black rags, dyed with an iron mordant and logwood,into claret. To strip the black dye from the rags, rendering them white ornearly so, and to produce upon them a claret shade, as would be done upon newmaterial, would be tedious and costly ; but the end is gained simply by boilingthe black rags with water to which a suitable proportion of claret spirit (p. 526)—a preparation of tin—has been added. On the fibre is a black compound ofoxide of iron and of the colouring matter of logwood. The chloride of tinattacks the iron, and removes it by reason of its superior affinity at once forthe wool and the colouring matter. What remains on the fibre is then aclaret-coloured compound of oxide of tin with the logwood. Thus the re-dyeingis effected without the use of any fresh dye-ware, one mordant having beenmerely substituted for another. Evenness of colour is not insisted on in caseof rag-dyeing, since, when the material has been torn up into shoddy, all itsirregularities disappear.

The re-dyeing of worn garments (job-dyeing) may be classed with piece-dyeing, and offers all the especial difficulties of the latter, heightened by the