270

DYEING AND CALICO PRINTING.

by a standard sample of madder of good quality. It is well to have an amplestock of that standard sample on hand, and to make simultaneously anexperiment with it, while it is also advisable to weigh off at least two quantitiesof each sample to be tried, and experiment upon them at the same time. Therelation between the mordanted surface of tissue and the tin&orial mattershould be so regulated that the mordant be not quite saturated, so as to leaveroom for the evaluation of dye material, which perhaps might be better thanthe standard. On the other hand, the degree of saturation must be such as toadmit of the proper estimation of the liveliness of the colours produced, andtheir fixity as regards the process of avivage or clearing : this latter operationis the more required to be performed with these samples, since it often bringsthe colours out in a manner different from their primitive brightness andintensity. The quantity of tissue—usually cotton—to be used in each expe-riment is 25 square centimetres, properly mordanted, and so treated as to bequite ready for use.* The quantity of madder is 10 grms., and of fleur degarance 5 grms., with a quantity of 1 litre of distilled water. When theexperiment is to be made with Alsace madder, a little chalk has to be addedto the water. The weighing off of the sample should be corredt at least within1 centigramme. The apparatus to be used and the manipulations to beemployed are as follows :—The samples of cotton which are marked by slits atthe margin, and the madder are placed in cylindrical glasses, capable of holdingat least 1-2 litres, and made of well-annealed glass. These are placed togetherin a large copper, the top being closed by a copper lid, perforated with cylin-drical openings large enough to admit the glasses to reach into the water.The best plan is to make the glass vessels rest on a perforated false bottom,and to immerse them to such a depth that only about £ an inch proje&s outat the top. The glass vessels should not be placed in the water-bath until itstemperature is 25 0 . At least two thermometers should be at hand : one toascertain the temperature of the water-bath, the other to test now andthen the temperature in the glass vessels. The heat is slowly raised from25°t095°during the lapse of two hours.f The latter degree is kept up for half anhour. It is very essential that a glass rod, not too thin, should be placed ineach glass vessel, and the contents stirred every five minutes, care being takento keep the cotton tissue entirely immersed and below the surface of theliquid. Every quarter of an hour the thermometer should be applied, to testthe degree of heat inside each vessel: after the lapse of two and a half hoursthe pieces of tissue are removed from the baths, rinsed in cold water to removeadhering particles of madder or dye-stuff, then washed in cold water, squeezedout, dried, and ironed with a smoothing-iron as used by laundresses, and nextcut with a pair of scissors in two equally sized parts, one of which is keptwithout further treatment, while the other is submitted to avivage or clearing.The first portion is pasted with one edge to a piece of paper, an open spacebeing left for the other half to be pasted in afterwards. The first pattern of

* On the Continent, in France and Belgium, tissue thus ready prepared and mordanted, inthe shape of stripes running parallel with the width of the cloth, and ready for red, pink, violet,lilac, &c., is sold in several of the larger towns.

+ Where steam can be had it is best to apply that to heat the water, since it is more easilyregulated than open fire: in the latter case charcoal and peat answer better than coals; gar.of course, may be applied where it is to be had.