In this form, the silk is technically called " dumb singles," because, being in the gum, it does not show up its lustre. Though it has no twist, it is sufficiently strong for the warp purposes of particular fabrics, such as gauzes, bandanas, ; it is sometimes used for weft purposes also. In both cases, it must be used in the natural gunk, as if it were attempted to clear it or dye it, to bring up the lustre or improve the colour, it would be rendered too soft and flossy for use. The silk is therefore cleared in these cases in the fabric, being boiled or dyed after manufacture. It is, how ever, sometimes "stained " by immersion in a cold dye-bath, when it ia necessary to get a coloured thread ; but in this case, the colour is neither so fast nor so lustrous as when treated in the other manlier.
Spinning and Doubling.—After the cleaning and the sizing process of the last stage, the thread is ready fur the spinning-machine, to which the bobbins are conveyed.
Assuming that organzine is required, the process is to spin or twist the " single " thread, com posed of the filaments reeled together from the cocoon. In this ease, it is customary to put about 15 turns au ineh for most descrip tions of work, though, in many instauces, this number is departed from, according to special requirement. In some cases, when singles are intended for organzine, 60 turns an inch are put in.
The spinning-machine, Fig. 1231, usually contains two tiers of spindles, one above the other, the whole amounting to several hun dred. The driving-shafts, one for each tier, carry eylindrieal tin drum extending the length of the frame. This drum actuates the spindles by means of driviug-bands, one for each spindle, which pass around it, and thence around the wharve upon the lower part of the spindle between the bolster and the footstep. Fig. 1232 shows the details of one of these spindles and its mountings : a is the footstep • in which the spindle b revolves, carrying the wharve c for the reception of the driving baud d. Midway in its height, the spindle passes through a bolster-rail e, fitted with brass bearings, in which it revolves. Just above the bearing, the spindle is tapered for the reception of the bobbin, tho smallest diameter being at the top. The bobbin f from the cleaning-machine, being adjusted upon the spindle, is firmly held upon the tapered part, and above it is mounted the flier g, composed of a small wooden boss, having a groove around its circumference, into which the wire forming the flier-a,rms is bent and secured. The extremities of this wire are curved to form eyelets for the reception of the thread. The traverse or guide-rail h is also fitted with eyelets.
In the process of spinning, the thread, both single and double, is conducted from the bobbin f through the lowest eyelet of the flier, around the limb h, through the upper eyelet, as well as that of the traverse-rail, and thence upon the bobbin i, whereon it is wound in crossed layers, as before, and for the same purpose. It will be observed that the course of the thread in silk-spinniug is the
reverse of that in other textile fabrics, being delivered instead of received by the bobbin upon the twisting-spindle. Should the thread be drawn from the bobbin f with the spindle at rest, one turn or twist would be imputed to it for every revolution drawn off. Suppose, however, the spindle to be making 6000 rev. a minute, and the draft of the bobbin to be 400 in. in the same time, it is obvious that this will give 15 turns for 1 in. of the thread, plus one turn for every rev. of the thread drawn from the bobbin required to yield 400 in. When single is being spun for organzine, and more twist is required, the draft of the bobbin i is diminished in proportion.
In silk-spinning, the flier is sometimes dispensed with, its chief use being to protect the thread from injury by friction during delivery from the bobbin, which some think is a more imaginary than real risk. As will be seen from the description of the machinery already given, and the nature of the silk filament or cocoon thread, the working of silk, especially in the throwing department, is exceedingly simple, consisting only of winding and twisting, and hardly affording much scope for the ingenuity of the raechanical inventor. Hence it is that improvements are comparatively rare and unimportant.
A machine, however, has recently been introduced for spinning or twisting purposes which is a considerable improvement upon preceding ones, owing to its productive capacity per spindle being double that of most others, thereby enabling considerable economy to be effected in space, waste, shafting, gearing, belts, buildings, and labour.
The structure of this machine, Fig. 1233, which can be adapted to any fibre, more nearly approxi mates to that of the bobbin-and-fly-frames, as used in cotton industry, than to machines employed in the silk manufacture. Risked of the bobbins containing the material to be tre,ated, reposing in a bank or creel on pegs, as usual, tlie machine is fitted with a creel or set of apindles which carry the bobbins containing the threads to be twisted, and these spindles are made to revolve at a great speed. Thus, running at the same rato as the front or twisting-spindles, which may be assumed to bo 4000 rev. a minute, half the twist ia put in before the yarn reaches the draft-rollers, when it becomes aubject to the action of the front spindles. These working at the usual speed, and having only half tho task to perform, it enables the rollers to be put on double speed, thus filling the bobbins in half the time, and ensuring a double production.