Cocoon harvesting and processing

Economic entomolgy

1. COCOON HARVESTING AND PROCESSING AEN 301- ECONOMIC ENTOMOLOGY Presented by P.Thirumoorthy M,Sc ( Agri ),GKVK

2. LATE AGE WORM REARING AND COCOON HARVEST 3 rd instar Cocoons after harvest Floss layer + Cocoon Larva on spinning Ripened worms 5 th instar 4 th instar

3. Netrika

4. Mounting appliances Rotary mountage Plastic collapsible mountage Bamboo chandrike New mountage

5. COCOON PROOCESSING

6. SELECTION OF THE COCOON Compactness : firm, compact and slightly elastic . Grain : Coarse granular cocoons make poor reeling . Weight of the cocoon : Quality of raw silk -reeled. Shell weight : Higher shell weight greater is the silk yield . Shell ratio : 12-24 %.

7. COCOON STIFLING / DRYING killing the pupa inside the cocoon Purpose : To avoid the moth emergence and thereby preserving the continuity of the silk filament. To protect the cocoon quality To preserve the cocoons for reeling Dried cocoons can be stored for a longer period without purification and moulds.  

8. Methods of stifling i ) Sun drying ii ) Stream stifling Basket steaming Chamber steaming iii) Hot air drying

9. Chamber steaming

10. Stifling chamber

11. COCOON STORAGE Air space for ventilation Humidity should not exceeds 70 % Temperature should be 27 o C

12. SORTING OF COCOONS Double cocoons, crushed and stained cocoons , cocoons with print of cocooning frame , flimsy cocoons , insect damaged cocoons , thin shelled cocoons, immature cocoons, pierced cocoons, are to be removed

13. COCOON MIXING / BLENDING producing high-grade raw silk It ensures speed and uniformity of reeling To obtain desired effect in raw silk Ensures a high degree of efficiency of automatic reeling machines

14. COCOON COOKING Pan cooking / Single pan cooking : Three pan cooking Pressurized cocoon boiling – conveyor cooking

15. BRUSHING / DEFLOSSING Hand brushing Mechanical brushing

16. REELING

17. REELING Charkha reeling Cottage basin Multi end reeling Automatic reeling machine

18. CROISSURE It is a mechanism of inter twining or crossing of two threads or one thread itself by twisting the threads in a series of spirals during its passage from the threader to the reel. ADVANTAGE To squeeze out excess water. To form a round, smooth and compact thread firmly agglutinated with an even coating of sericin .

19. REREELING It is to transfer the raw silk reeled on small reels to a large reel 91.5m circumference) to set uniform width, weight and length of the skein. Purpose: To eliminate gum spots in the reeled silk To tie up any loose ends to form continuous silk thread. To ensure smooth and efficient operation during the winding process

20. WINDING To put the yarn in a long continuous length to suit the weaving processes. It eliminates imperfections such as slubs , weak places, dirt and so on . Quality of the silk thread in the bobbin is comparatively better than that on the hank.

21. REWINDING Bobbins produced on twisting machine are placed on the rewinding machine and the thread is rewound on to the double flanged bobbins The rewound bobbins are fed to the warping machine for preparing warp beams .

22. DOUBLING Individual threads are doubled To avoid unevenness increase the strength of the yarn . It is done using doubling machine

23. TWISTING Twisting may be done in single thread The direction of twist and the twist rate depends on the type of yarn . Twisted bobbins should be hot set before use (Heat setting/steaming ).

24. DEGUMMING Removal of gum or sericin is termed as degumming. The different methods Soap and soda method Enzymatic method of degumming

25. BLEACHING OF SILK Removal of natural pigmentation Silk whiteness can be improved by bleaching with reducing agents like hydrosulphite and rongalite or oxidising agents like potassium permanganate, sodium peroxide and hydrogen peroxide . The process of bleaching Boiling the material concerned for 2 h with 1-2 volumes of hydrogen per oxide concentration with 2g/l sodium silicate followed by a hot wash.  

26. DYING Silk has an affinity for various classes of dye stuffs acid dyes Direct dyes Metal complex dyes Milling dyes Reactive dyes

27. LACING passing a thread across the skein in such a way as to divide into five equal parts with the purpose of keeping the threads in place to ensure the thread lacing unwound easily.

28. SKEINING Twisting of raw silk several times. A skeining machine or a turner does skeining .   BOOK MAKING Twisted skeins are packed bundles of 2 kgs and they are known as books. Books are packed in bales. Indian silk bales is 20 kgs .

29. REFERENCES lntroduction to silkworm rearing by Japarr Silk Association, Inc'' Japau ' L96j Sericultural malual on silkworm rearitrq b1'S' Krishnaswami , M'N'Narasimhanna . s.K . Suryanarayan , atttl S. Kutnararaj , FAO, AgricultLrral ServiceBulletin . Roarn , 1973