MADDER LAKE 175 



completely incorporated with and fixed in the fibre. It has generally been found 

 desirable that calico printed with a mordant should, before dyeing, bo exposed to the 

 atmosphere for some time in the ageing room, in single folds, which generally speak- 

 ing, requires several days, the object being to liberate the acetic acid from the acetates 

 of iron or subacetates of alumina, and to oxidise the protoxide of iron. It was for 

 many years believed that oxygen was the only necessary agent ; and although some 

 printers had observed that moisture facilitated the process, this fact was not generally 

 known until Mr. J. Thoiu of Manchester claimed the introduction of moisture as an 

 important agent in the process of ageing, in a patent which he took out in 1849. Mr. 

 W. Crum was, however, the first printer who applied this principle practically. He 

 describes the process as adopted at Thornliebank (near Glasgow), in the following 

 words : A building is employed, 48 feet long inside and 40 feet high, with a mid- 

 wall from bottom to top, running lengthwise, so as to form two apartments, each 1 1 

 feet wide : in one of these apartments the goods first receive the moisture they require. 

 Besides the ground floor, it has two open sparred floors, 26 feet apart, upon each of 

 which is fixed a row of tin rollers, all long enough to contain two pieces of cloth in 

 their breadth. The rollers being threaded, are set in motion by a small steam-engine, 

 and the goods to be aged, which are at first placed in the ground floor, are drawn into 

 the chamber above, where they are made to pass over and under each roller, issuing 

 at last at, the opposite end, where they are folded into bundles on one of the three 

 stages which are placed there. These stages are partially separated from the rest of 

 the chamber by woollen cloths. While the goods are traversing these rollers they are 

 exposed to heat and moisture, furnished to them by steam, which is made to issue 

 gently from three rows of trumpet-mouthod-shaped openings. The temperature is 

 raised from 80 to 100 F. or more, a wet-bulb thermometer indicating at the same 

 time 76 to 96 F.. or always 4 less than the dry-bulb thermometer. In this arrange- 

 ment 50 pieces of 25 yards each are exposed at one time ; and, as each piece is a 

 quarter of an hour under the infhience of steam, 200 pieces pass through in an hour. 

 Although workpeople need scarcely ever enter the warmest part of this chamber, a 

 ventilator in the roof is opened when thei'e is any considerable evolution of acetic 

 acid. The mordant does not, however, become fully aged by this process alone, 

 although it is acted upon as much as if it had hung a whole day in cold air. It has 

 received, however, the requisite quantity of moisture, about 7 per cent, of the weight 

 of the piece, and is thus enabled, if the mordant be iron, to take oxygen from the air, 

 and to become changed with time into the sesquiacetate and sesquihydrate of oxide of 

 iron. In order to be sufficiently aged, it must be left one, or two, or even three, days 

 in an atmosphere still warm and moist. 



' It had been ascertained long before, at Thornliebank, that exposure in single folds, 

 after moistening, was not necessary. The experiments of the late Prof. T. Graham, 

 on the diffusion of gases through small apertures, had served to suggest that, for the 

 absorption of the small quantity of oxygen required, the goods might as well be 

 wrapped up and laid in heaps. Accordingly, in the operation in question, the 

 moistened goods are carried in bundles into the building on the opposite side of the 

 mid-wall already mentioned, and laid upon the sparred floors, placed at heights cor- 

 responding with the stages in the first apartment. Upon these floors, 7,000 or 8,000 

 pieces may be laid at a time, and, since each piece is 25 yards long, 100 miles can be 

 stored at once. It is necessary, of course, that an elevated temperature and a corre- 

 sponding degree of moisture be preserved in the storing apartments, day and nighl, 

 and 80 F. is sufficient with the wet-bulb thermometer at 76. To effect this condition, 

 a largo iron pipe is placed along the ground floor underneath, and moderately heated 

 by steam, while a row of small jets in the same position are made to project steam 

 directly into the air of the room. The whole building is protected from external cold, 

 and consequently from condensation of steam, by a warmed entrance-room, and by 

 double windows, thick walls and a double roof. Small steam-pipes are also placed at 

 other points, where they seem to be required ; and the apartment which contains the 

 rollers is specially heated when not in use by a couple of steam-pipes, which are placed 

 under the ceiling of the ground floor.' 



All who are interested in the application of mordants, and who arc- desirous of 

 understanding the principles upon which the applications are made, are referred to 

 the ' Handbook of Dyeing,' already quoted. 



MADDER XiAXE. The red pigment usually called madder lake, which is miich 

 used by painters, is made by treating madder, which has been previously washed with 

 water, with a boiling solution of alum, filtering the red liquid, and adding a small 

 quantity of carbonate of soda, taking care to leave an excess of alumina in solution, 

 washing the red precipitate, which is a compound of colouring-matter and alumina, 

 with water and drying. Persoz gives the following method for obtaining a madder 

 lake of great brilliancy : One part of madder, which has been previously sub- 



