DUNGING

in calico-printing, is the application of a bath of cowdung, diffused through hot water, to cotton goods in a particular stage of the manufacture. Dunging and scouring are commonly alternated, and are two of the most important steps in the proce . The operation of dunging has for its objects :— 1. To determine the entire combination of the aluminous sub-salts with the stuffs, by separating almost all the acetic acid which was not volatilized in the stove-drying of the mordant. 2. To di olve and carry off from the cloth a portion of the thickening matters. 3. To separate from the cloth the part of the mordant that is uncombined, and merely mixed mechanically with the gum or starch. 4. To prevent, by the peculiar action of the dung, the uncombined mordant, as well as the acetic acid with which the bath is apt to get loaded, from affecting the blank parts of the cloth, or being injurious to the mordant. The aluminous base or mordant on the cloth, more or le neutralized by the dunging, is next subjected to the dash-wheel or fulling mill, where by the stream of water the remainder of the thickening and other impurities are washed away. No very exact analysis has been made of cowdung. Morin’s, which is the most recent and elaborate, is as follows :— | Water | 70·00 | | Vegetable fibre | 24·08 | | Green resin and fat acids | 1·52 | | Undecomposed biliary matter | 0·60 | | Peculiar extractive matter ( bubu line ) | 1·60 | | Albumen | 0·40 | | Biliary resin | 1·80 | According to M. Kœchlin’s practical knowledge on the great scale, it consists of a moist fibrous vegetable substance, which is animalized, and forms about one-tenth of its weight; 2. of albumen; 3. of animal mucus; 4. of a substance similar to bile; 5. of muriate of soda, muriate and acetate of ammonia, phosphate of lime and other salts; 6. of benzoin or musk. Probably the hot water in which the calico-printer diffuses the dung, exerts a powerful solvent action, and in proportion as the uncombined mordant floats in the bath it is precipitated by the albumen, the animal mucus, and the ammoniacal salts; but there is reason to think that the fibrous matter in part animalized or covered with animal matter, plays here the principal part; for the great affinity of this substance for the aluminous salts is well known. All practical men are aware that the affinity of cotton for alumina is increased by its combination with oil or animal substances, to such a degree as to take it from the dung bath; which would not be po ible without this combination. It would therefore appear that the principal function of dunging is to hinder the uncombined mordant, diffused in the dung bath, from attaching itself to the unmordanted portion of the cloth, as already observed; for if we merely wished to abstract the thickening stuffs, or to complete by the removal of acetic acid the combination of the aluminous base with the goods, dung would not be required, for hot water would suffice. In fact, we may observe, that in such cases the first pieces pa ed through the boiler are fit for dyeing; but when a certain number have been pa ed through, the mordant now di olved in the water is attracted to the white portions of the cloth, while the free acid impoverishes the mordanted parts, so that they cannot afford good dyes, and the blank spaces are tarnished. The cow dung may be in some measure replaced by bran, but not with perfect succe . The former both answers the purpose better and is cheaper. The bran is only preferred for the most delicate yellows, for cochineal pinks and lilacs, to which the dung may sometimes impart a greenish cast. It is to be presumed that the action of the bran in this proce has much analogy with that of the dung, and that the ligneous fibre is the most active constituent; with which the gluten and mucilage co-operate, no doubt, in seizing the aluminous salts. It seems to be ascertained that the mordant applied to the cloth does not combine entirely with it during the drying; that this combination is more or le perfect according to the strength of the mordants, and the circumstances of the drying; that the operation of dunging, or pa ing through hot water, completes the combination of the cloth with the aluminous base now insoluble in water; that this base may still contain a very minute quantity of acetic acid or sulphate of alumina; that a long ebullition in water impoverishes the mordant but a little; and that even then the liquid does not contain any perceptible quantity of acetate or sub sulphate of alumina. The manner of immersing the goods, or pa ing them through the dung bath, is an important circumstance. They should be properly extended and free from folds, which is secured by a series of cylinders. The cistern is from 10 to 12 feet long, 4 1 ⁄ 2 feet wide, and 6 or 8 feet deep. The piece pa es alternately over the upper rollers and under rollers near the bottom. There are two main squeezing rollers at one end, which draw the cloth through between them. Whenever the goods come out of the bath they are put into the dash-wheel. The immersion should take place as fast as po ible, for the moment the hot water penetrates the mordanted cloth, the acetic acid quits it; and, therefore, if the immersion was made slowly or one ply after another, the acid as well as the uncombined mordant become free, would spread their influence, and would have time to di olve the aluminous subsalts now combined with the cloth; whence inequalities and impoverishment of the colours would ensue. It is difficult to determine the number of pieces which may be pa ed through a given quantity of dung and water. This depends upon the state of the mordants, whether they are strong or acid, and on the quantity of the surface covered with the figures. The number varies usually from 20 to 60 pieces, for from 240 to 300 gallons of water and 6 gallons of dung. The time of the immersion varies with the concentration of the mordants, and the nature of their thickening. The temperature must be regulated by the same circumstances; for starch or flour paste a much warmer bath is needed than for gum. The heat varies usually from 130° to 212° F. When the printing is heavy and the thickening is starch or flour, the goods are usually twice dunged, with two washings between the two dungs. A strong acid mordant is more difficult to dung and to wash than a neutral mordant, especially when it is to receive the madder dye. Sometimes a little chalk is added to the bath, when the goods have been padded in an acid mordant. Too much dung is injurious to weak mordants, as well as to pinks. It has also been remarked that a mordant when neutralized does not produce as brilliant tints, especially yellows. The latter are obtained of a finer shade when, instead of dunging, they are exposed for an hour in a stream of water, provided its temperature is not too low. In winter they are pa ed through a slightly chalky water, then washed at the wheel, and dyed in quercitron or weld. A very able and learned memoir upon this subject, by M. Penot, Profe or of Chemistry, appeared in the Bulletin of the Society of Mulhausen, in October, 1834, with an ingenious commentary upon it, under the title of a Report by M. Camille Kœchlin, in March, 1835. Experience has proved that dunging is one of the most important steps in the proce of calico printing, and that if it be not well performed the dyeing is good for nothing. Before we can a ign its peculiar function to the dung in this case, we must know its composition. Fresh cow’s dung is commonly neutral when tested by litmus paper; but sometimes it is slightly alkaline, owing, probably, to some peculiarity in the food of the animal. The total constituents of 100 parts of cow dung are as follows: Water, 69·58; bitter matter, 0·74; sweet substance, 0·93; chlorophylle, 0·28; albumine, 0·63; muriate of soda, 0·08; sulphate of potash, 0·05; sulphate of lime, 0·25; carbonate of lime, 0·24; phosphate of lime, 0·46; carbonate of iron, 0·09; woody fibre, 26·39; silica, 0·14; lo , 0·14. In dunging calicoes the exce of uncombined mordant is in part attracted by the soluble matters of the cow’s dung, and forms an insoluble precipitate, which has no affinity for the cloth, especially in presence of the insoluble part of the dung, which strongly attracts alumina. The most important part which that insoluble matter plays, is to seize the exce of the mordants, in proportion as they are di olved by the water of the bath, and thus to render their reaction upon the cloth impo ible. It is only in the deposit, therefore, that the matters carried off from the cloth by the dung are to be found. M. Camille Kœchlin ascribes the action of cow dung chiefly to its albuminous constituent, combining with the alumina and iron, of the acetates of these bases di olved by the hot water of the bath. The acids consequently set free, soon become evident by the test of litmus paper, after a few pieces are pa ed through, and require to be got rid of either by a fresh bath or by adding chalk to the old one. The dung thus serves also to fix the bases on the cloth, when used in moderation. It exercises likewise a dis oxidating power on the iron mordant, and restores it to a state more fit to combine with colouring matter.