Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/765

certain heat. In the case of the regular steam colours and aniline dyes there is printed on the cloth a chemical mix ture or solution, which on the application of heat produces a reaction resulting in the precipitation of an insoluble compound in the fibres, or a volatilization of the solvent medium is caused, so that in both cases the same result

an insoluble precipitate is produced.

With the development of steam colours efforts have been made with success to improve on the original crude and unsatisfactory manner in which the steaming was performed. The old method, still largely employed, consists in wrap ping the printed cloth around a perforated cylinder of copper, called a " column," into one end of which a pipe passes for the admission of steam. Around the column are first wrapped several folds of felt, above which comes white calico, next the printed goods, and lastly an outer envelope of white calico. When so prepared the column is set perpendicularly on a steam pipe, a stop cock is opened, and steam is admitted into the interior of the column, which presses through and acts on the printed goods. Immediately on the conclusion of the process the column must be dismounted and the goods run off, otherwise steam might condense in the cloth and cause certain colours to run.

The most common arrangement for steaming, however, consists of the chest or " cottage," which is a cylindrical steam-tight chamber, into which a carriage is introduced. The carriage is mounted with a series of rollers on which the pieces to be steamed are hung, or, in a different arrange ment, the cloth is fastened on a range of hooks projecting from a .steam pipe. In the latter arrangement the hooks are heated by steam before the carriage is thrust into the chest, to prevent condensation of steam on the cold spikes, and consequent rust-staining of the cloth. Fig. 7 shows a sectional view of an ordinary steaming chest by Messrs Mather and Platt. A represents the body of the chest ; B the steam-tight door, which draws up when the chamber is to be opened ; C the carriage or waggon fitted with a range of square wooden rollers E. The rollers are all geared to move by means of a cog-wheel F, which is turned by the attendant outside the chamber. The carriage is run in upon the rails D ; steam is admitted by the perforated steam-pipe G ; H is a tap for running off condensed water, and J is a safety-valve. While one carriage is in the chamber another is being filled and prepared outside to take its place when the goods are sufficiently steamed.

FIG. 7. Section of Steaming Ghost.

The steaming chest is at best only a crude and discon nected manner of performing one process in printing, and as all the others arc continuous, it forms an awkward break in the series. To obviate this, and to secure expedi tion and continuity, a method of steaming has been devised by M. Cordillot of Moscow and Mr William Mather of Salford, which they patented in 1874. Their apparatus, of which a sectional illustration is shown in fig. 8, they claim will effectually steam 1000 pieces of 25 yards per day. According to their specification, it consists of "a brick or other chamber a, the roof of which is lined with a curved steam jacket l>, connected by side pipes c c to the perforated pipe d near the floor. At each end of the chamber a is an opening closed by a steam-tight door e, through which openings the waggons for receiving the steamed fabrics are admitted and discharged. The fabric is fed into the chamber a over the feed roller g and between the small guide roller or tube h and copper troughs i and i, both of which and the tube h are heated by steam and project on each side of the wall to collect any moisture that may run down. When the fabric is in the chamber it is carried around three or other convenient number of rollers marked j, the last of which delivers it into one of the waggons /." The rollers are all heated by steam to prevent condensation, and as very moist steam is required for some colours, the supply pipe passes through water before entering through the pipes q into the curved jacket b, and thence going by the side pipes c c into the perforated pipe d as before described. " When the apparatus is in operation the steamed fabrics are deposited in one of the waggons, as shown in the figure, and when one is full both end doors are opened to allow the last waggon near the left- hand door to be discharged and to move the full waggon one step, towards the exit door by the introduction of an empty waggon through the right-hand door ; this brings another waggon in position for receiving the steamed fabrics, and while this is being filled the full waggon (after the four empty ones introduced to fill up the chamber at starting have passed through) that had been discharged can be emptied and brought back to the entrance door." The waggons are made of strong wire and are heated up before entering the chamber. By this system the patentees affirm that the goods are long enough exposed to the steam to allow the chemical reactions to take place in the cloth, so that the colours neither print off nor run during the remainder of the process, and the fixation is completed while the goods lie in the waggons inside the chamber. This system of steaming is in successful operation in some Manchester print-works.

Fid. 8. Cordillot and Mather s Steaming Apparatus.

Steam colours include two distinct classes of work 1st, pigment colours, or the series fixed by a mechanical effect produced in steaming ; and 2d, ordinary steam colours, in which the fixation is effected more by chemical agency.