WO2005049899A1

WO2005049899A1 - Manufacture of silk

Info

Publication number: WO2005049899A1
Application number: PCT/GB2004/004797
Authority: WO
Inventors: Sally Barton; Shankar Bashetteppa Dandin; Gandudi Krishnaiah Srinivasa Babu
Original assignee: Central Sericultural Research And Training Institute
Priority date: 2003-11-14
Filing date: 2004-11-12
Publication date: 2005-06-02
Also published as: GB0326645D0; EP1689917A1; IN2014DN06932A

Abstract

A method of making silk comprising the steps of disposing a silkworm on a substantially flat surface (61) which is sufficiently free of anchor points that the silkworm cannot spin a cocoon thereon. The silkworm is able to move around on the surface (61) whilst secreting silk thread, thereby forming a mat of silk on the surface. After the formation of a mat (51, 52) of silk the silkworm is removed from the surface. The mat (51, 52) of natural silk comprises a continuously spun thread extending in multiple paths across the area of the mat in a pattern of crossing thread portions. In an advantageous embodiment, the surface (61) is held at an angle (α) to the horizontal whereby the silkworms tend to climb up the surface (61).

Description

Manufacture of Silk

The present invention relates to a method of making silk and silk produced thereby.

Traditionally silk has been obtained from cocoons made by silkworms which are caterpillars of the silk moth, Bombyx Mori. Silkworms, when ready to pupate will normally spin silk around themselves to make the cocoon which comprises upto a mile and a half of continuous thread. When the pupa has metamorphosised into a moth and is ready to leave the cocoon, it secretes an alkali which corrodes a hole in the cocoon through which the moth may exit. This renders the thread discontinuous and consequently of little use in standard silk production techniques. To overcome this problem, the pupae are normally killed in the cocoon before completion of the metamorphosis, by heating them or by suffocating them e.g. with steam. A small proportion of the silkworms are allowed to complete their metamorphosis, whereafter breeding occurs. Hence, the traditional production of silk requires the death of the silkworm which is seen by many people as unacceptable.

For a silkworm to make its cocoon, it requires anchor points to which it attaches the silk thread so that the cocoon has physical support during its construction. The silkworm will generally not begin spinning until it finds suitable anchors. It has been known to use cardboard grids, for example, which are simply placed near the silkworms. The silkworms then attach their thread to the walls of the grid (See Fig. 1).

In the prior art processes, the cocoons, after destruction of the pupae therein, are unwound by locating an end of the silk thread and unwinding the cocoon by attaching the end of the thread to a winding bobbin. The silk from several cocoons may be wound together to make one strong silk thread. The thread is then woven into cloth.

The present invention provides a method of making silk comprising the steps of disposing a silkworm on a substantially flat surface which is sufficiently free of anchor points that the silkworm cannot spin a cocoon thereon, the silkworm being able to move around on the surface whilst secreting silk thread thereby forming a mat of silk on the surface, and removing the silkworm from the surface after the formation of a mat of silk.

Due to the fact that the surface is substantially flat and sufficiently free of anchor points, the silkworm cannot find a suitable place to begin spinning its cocoon, so it continues to move around searching for an anchor. However, the silkworm cannot ultimately control its silk glands and sooner or later the silk must be released. The silk emerges from a small spinneret on the silkworm's lip. Whilst this is occurring, the silkworm is still searching and silk thread is deposited on the surface following the random movements of the silkworm. Eventually, a mat of silk lies on the surface. None of the further processing of the silk associated with the prior art, such as winding into thread and then weaving into cloth is required.

The worm can be of any appropriate species e.g. Bombyx Mori, the main requirement of the worm being that it produces silk or other material. For instance, species are known which produce a material of a rougher texture than silk, similar to sacking cloth, and these too could be used in the present invention. Hence, references herein to "silkworms" and "silk" are to be construed accordingly. The mat or patch of silk produced on the surface is advantageously removable from the surface and is strong enough to be dry cleaned or washed conventionally.

After removal of the silkworm from the surface, the silkworm can be stored in conditions suitable for metamorphosis to occur, despite the fact that it has no cocoon. In this respect, the silkworm can be wrapped in a thermally insulating material such as cotton wool or bubblewrap.

The surface can be arranged substantially horizontally and on support means which advantageously ensures the silkworm does not escape. The surface can advantageously be made of card, which is cheap and can be easily cut to a desired shape. A cloth, such as hessian can also be used having similar advantages. Any material sensible to the skilled person could be used.

The present invention also provides a mat of natural silk comprising a continuously spun thread extending in multiple paths across the area of the mat in a random pattern of crossing thread portions. The mat can have a predetermined peripheral edge shape.

To achieve a reasonable mat thickness with the silk produced by a single worm it is appropriate for the area of the surface on which the worm is placed, and hence that of the mat produced, to be not greater than about 4 to 6 sq. ins (25 to 40 sq. cm). The smaller the area of the surface, the more intense is the silk thickness obtained per worm. For instance, rectangular silk mats can be produced on a surface area measuring about 3 x 2 ins (8 x 5 cms) with the silk from a single worm resulting in a very acceptable thickness over the entire surface area including the corners. Square surfaces of a similar area also give desirable results. Many other shapes of mat can also be produced, as discussed in the detailed description below. If desired, when a worm has finished spinning its silk onto the surface, and is removed from the surface, a second worm can be placed onto the surface and the silk mat produced by the first worm in order to lay down a second layer of silk. In this way the thickness of the silk mat can be built up to a desired level before the finished mat is removed from the surface. Indeed for particularly large surfaces, it is necessary to use a plurality of silkworms, to ensure that the mat is thick enough and hence strong enough to be removed and utilised. For instance, with a surface measuring 12 x 12 in (30 x 30 cm) the silk of approx. 30 worms gives an acceptable thickness, although more worms can of course be used to obtain a thicker mat if desired. In most cases, it is desirable to use a plurality of silkworms, especially if the surface has an area greater than 6 sq. in (40 sq. cm). The first series of worms ensures coverage of the surface with silk, whilst the subsequent worms are used to build up the thickness.

In a particularly advantageous development of the method according to the invention, the surface can be arranged at an angle to the horizontal, the silkworm being disposed on a lower portion of the surface, and having a natural tendency to climb up the surface. When the silkworm has reached an upper portion of the surface, the surface and/or the silkworm can be rearranged so as to re-dispose the silkworm on a lower portion of the surface. By virtue of this guiding of the silkworm's movement some correlation can be achieved between the orientation of the numerous silk threads, thereby giving improved aesthetic qualities to the silk produced. An alignment of the threads may also improve the strength of the resultant mat of silk, particularly along the direction of the threads. Furthermore, an even coverage of silk on the surface is thereby ensured. In another variant on the method, for making flat silk, the traditional cocoon spinning frames, comprising an array of boxes each adapted to receive a silkworm can be utilised. It has been observed that if a silkworm cannot find a box in the frame, it will spin silk over the top of one or more boxes, thereby creating a roughly circular shaped web of silk thread on the box. This can be exploited by providing a frame which is already full of silkworms and then adding extra silkworms onto the frame.

Other advantageous optional features of the invention are set out in the dependent claims. Embodiments of the invention are described below in detail, with reference to the accompanying drawings in which

Figure 1 shows a cardboard grid containing cocoons as used in prior art methods;

Figure 2 is a perspective view of an apparatus usable in the invention;

Figure 3 a is a perspective view of a surface and a silkworm;

Figure 3b is a perspective view of a mat of silk on the surface;

Figure 4 shows a pair of silkmoths; and

Figure 5 A and 5B show plan views of silk mats embodying the invention.

Figure 6 is a schematic side view of a second apparatus usable in the invention.

Figure 7 is a schematic side view of the apparatus of figure 6 in a different configuration.

Figure 8 is a perspective view of the apparatus shown in figure 7.

In Fig. 1 is shown a cardboard grid 11 containing a plurality of cocoons 12, as known from the prior art and discussed above.

Fig. 2 shows an example of an apparatus which can be used in the present invention. A silkworm 23 is shown disposed on a flat surface 21, which here is made of card, and which is arranged on support means 22, here in the form of a bottle. The silkworm is to be placed on the surface when it is ready to start spinning silk which is marked by the silkworm turning a translucent yellow colour. As it is unable to find any anchor points, the silkworm weaves silk onto the surface 21. In Fig. 3 A can be seen a silkworm which has started to spin silk on surface 21. The silk thread 31 is deposited on the surface as the silkworm 23 moves around thereon.

In Fig. 3B a completed mat of silk 32 lies on the surface 21. The mat 32 is then removed from the surface by simply peeling it off and can then be washed or dry-cleaned. The shape of the mat 32 is substantially the same as that of the surface 21. It is known for the mat sometimes to have a slightly thicker deposit of silk at its periphery, when the silkworm has spent more time near the edges of the surface, trying to find anchor points. However, the mat 32 may also be of uniform thickness. The mat 32 comprises a continuous thread extending along paths following the random movement of the silkworm 23.

The spinning process is allowed to go on for VA to 2 days, the silkworm becoming weak and vulnerable as this goes on. A glue is secreted with the silk at the time of spinning and this sticks the silk threads together. After spinning, the silkworm is removed from the surface and placed in protective material such as cotton wool or bubble wrap, so that metamorphosis can occur. Metamorphosis takes approximately three weeks, after which moths emerge. Silkmoths cannot fly, they never eat or drink and they will mate and die within five days of emerging.

In Fig. 4 is shown a pair of silkmoths 41, 42 which have mated and the female 42 has laid her eggs 43. The eggs 43 can be refrigerated for a matter of years and, once removed will hatch in six to twenty days. The silkworm then eats mulberry leaves preferably, for about 26 days before spinning of the silk begins. It takes about three days for the silkworm to turn into a pupa. As mentioned, the silkworm is allowed to spin silk for one and a half to two days and is then placed in cotton wool or bubblewrap, the metamorphosis taking about 21 days. They then mate and the females lay eggs and the moths then die.

Fig. 5 A shows schematically a mat 51 wherein the edge portions 53 can be seen to have a higher silk density than the central areas of the mat 51. Fig. 5B shows schematically a differently shaped mat 52 whereby the edge 54 of the mat 52 has a higher density of silk than elsewhere on the mat. Any shape of mat can be produced, including substantially square or rectangular, or other polygonal shape, as long as the corresponding surface does not provide anchor points to the silkworm or silkworms thereon. The surface can also be a long strip. On larger surfaces, there is a tendency for the worms to skimp the corners, thus not depositing as much silk there, especially if the comer is a sharp one. However, on smaller surfaces, due to the movement of the silkworm being more restricted, the silkworm deposits silk more evenly over the whole surface and does not skimp comers. It is of course possible to trim the edges of the mat of silk if desired. The minimum size surface that can be used is governed by the need to hold a silkworm thereon so that it does not fall off. Hence this size is of the same order as the size of the silkworm to be used. For larger surfaces, more silkworms and more time are required to produce the mat of silk, but there is no particular theoretical maximum size.

A second apparatus usable in the invention is shown in Figure 6. In this apparatus, the surface 61 can be inclined to the horizontal. This is useful because it has been observed that silkworms have a natural tendency to climb upwardly, looking for a suitable anchoring location. Thus, the silkworm(s) can be placed at the bottom of the slope and will move upwards while spinning silk thread with the result that the silk threads are to some degree aligned with one another. A more even coverage of silk results also, because as the silkworm or silkworms are biased towards a particular direction they head in this direction and do not spend as much time searching near the edges of the surface. When the silkworm(s) reach the top, the surface is rotated back around, so the silkworm(s) are at the bottom again. The apparatus comprises a surface 61 mounted on an axle 62. The axle 62 is joined to a shaft 63 via a joint 64. The joint 64 is of any type suitable to allow pivoting of the axle 62 about the joint and rotation of the axle 62 about its longitudinal axis, whereby the surface 61 can be pivoted to any desired slope and can also be rotated in its own plane. In the embodiment shown, the shaft is mounted in a bearing 65 in the joint 64. It would also be possible to have a first joint (not shown) allowing pivoting of the axle, and a second separate joint (not shown) located between the axle and the surface, allowing rotation of the surface in its own plane. By virtue of the surface being rotatable in its own plane, when the silkworm or silkworms reach the top end of the surface, the surface can rotate under the weight of the silkworm(s) themselves, thereby providing an automatic rotation of the surface at the appropriate time. Alternatively, the surface can be rotated by hand. In a particularly simple alternative the surface 61 can simply be attached directly to the top of the shaft 63 via a hinge (not shown) allowing the pivoting of the surface, without the need for the axle.

Figure 7 shows the apparatus of Figure 6 in an inclined position wherein the surface 61 is at an angle α to the horizontal. The angle α is optimally between 35° and 40° to ensure the silkworms recognise the upward direction, without being so steep that the silkworms fall off the surface 61. The angle α is chosen by pivoting the surface 61 and the axle 62 about the pivot 71, and the surface can be fixed at a given angle by tightening a screw 72.

In Figure 8, the silkworms 81 can be seen at an upper portion of the sloped surface 61, at which point the surface is rotated in the direction shown by the arrow 82.

Claims

1. A method of making silk comprising the steps of disposing a silkworm on a substantially flat surface which is sufficiently free of anchor points that the silkworm cannot spin a cocoon thereon, the silkworm being able to move around on the surface whilst secreting silk thread thereby forming a mat of silk on the surface, and removing the silkworm from the surface after the formation of a mat of silk.

2. A method according to claim 1, wherein after removal of the silkworm the mat of silk is removed from the surface.

3. A method according to claim 1 or 2, wherein after removal of the silkworm, the silkworm is stored in conditions suitable for metamorphosis to occur.

4. A method according to claim 3, wherein the silkworm is wrapped in a thermally insulating material.

5. A method according to any one of the preceding claims, wherein the surface is raised above its surroundings.

6. A method according to claim 5, wherein the surface is arranged substantially horizontally on support means.

7. A method according to claim 5 or 6, wherein the support means is situated to avoid being reachable by the silkworm.

8. A method according to any one of the preceding claims, wherein the surface has an area of at least 25 to 40 sq. cm.

9. A method according to any one of claims 1 to 8, wherein the surface is substantially square or rectangular in shape.

10. A method according to any one of the preceding claims, wherein the shape of the mat is substantially the same as the shape of the surface.

11. A method according to any one of the preceding claims, wherein the mat is washable and dry-cleanable.

12. A method according to any one of the preceding claims, wherein the silkworm is disposed on the surface when it is about to start spinning silk.

13. A method according to any one of the preceding claims, wherein two or more silkwonns are disposed on the surface.

14. A method according to claim 13, wherein the silkworms are disposed on the surface in succession, each silk worm being replaced by the next when it has finished secreting silk.

15. A method according to any one of claims 1 to 5, wherein the surface is arranged at an angle to the horizontal.

16. A method according to claim 15, wherein the angle of inclination of the surface is between 35° and 40°.

17. A method according to claim 15 or 16, wherein the silkworm is disposed on a lower portion of the surface and when the silkworm has reached an upper portion of the surface, the surface and/or the silkworm is rearranged so as to re- dispose the silkworm on a lower portion of the surface.

18. A method according to claim 17, wherein the silkworm is re-disposed on a lower portion of the surface by rotating the surface about an axis.

19. A method according to claim 18, wherein the surface is rotated through about 180°.

20. A method according to claim 18, wherein the surface is rotated by substantially less than 180°.

21. A mat of natural silk comprising a continuously spun thread extending in multiple paths across the area of the mat in a pattern of crossing thread portions.

22. A mat of natural silk according to claim 21, wherein the crossing thread portions are oriented randomly with respect to one another.

23. A mat of natural silk according to claim 21, wherein the crossing thread portions have a degree of mutual alignment.

24. A method of making silk substantially as herein described with reference to the accompanying drawings.

25. A mat of natural silk substantially as herein described with reference to the accompanying drawings.