Cocoon quality and cocoon filament

Introduction

Indian silk suffers from variation in the denier which breaks during winding and weaving and thus is not preferred as a warp in the powerloon, while the chinese silk having betters strength, colour and shine is used without twist for higher production efficiency. If Indian silk can be better with respective denier uniformity and strength, it can be used in powerloon as it has a better luster and dye affinity. At present, multi end machine are not installed in any of the big factories but are used by the small reelers who can produce only a small quantity of multi-bivoltine silk. What is needed is private sector investment or producing large quantities of row silk (C-2A grade) to feed the powerloon sector. The bivoltine hybrids which promised quality, silk as well as increased production have not been explotted in this decade. Therefore it is necessary to switch over to sustainable highly productive bivoltine silkworm breeds which can give 2A-4A grade international quality silk. The rearers will get the price for their product depending upon the quality of cocoons they produce.

Factors affecting the quality of cocoons

The main considerable commercial characters of cocoons for price fixation are:

• Colour

The colour of cocoon depends upon the presence of coloured pigments in the sericin layer. Properly stifled cocoons will be brighter and dullness indicate the improper stifling.

• Compactness

Compactness of cocoon is an important character that indicates the quantity of silk present in the cocoon. Compact, slightly resilient firmness of cocoon when felt by light press indicates the good commercial quality of cocoon.

• Cocoon weight

The weight of cocoon is one of the important commercial character considered in price fixation. The green cocoon weight will be decreased day by day until moth emerges out.

• Denier

Thickness of silk filament is denoted by denier. The denier size of outer most layer of cocoon i.e. floss layer will be higher than the inner most pelade layer.

• Grain or wrinkle

A deflossed cocoon should not show grain or wrinkles. Which are not easily reelable. Cocoons with finer granulations are easy to reel.

• Length of silk bave

Indian multi voltine races contain 300-400 mts

Indian multi voltine hybrids 400-550 mts

Newly evolved hybrids 600-800 mts

Uni/Bi-voltine hybrids 1000-1500 mts

• Reelability

Reelability is the ratio of cocoons reeled without break and the total number of cocoons utilised. Frequent breakage results in wastage of raw material and wastage of time, hence, skill labour, quality cocoons are essential.

• Shell Ratio

The quantity of silk can produced from each cocoon depends upon the weight of shell. Therefore, necessarily it is important to calculate the shell ratio. The cocoon weight includes the weight of shell and weight of pupa inside.

S.R.%= Wt.of cocoon shell/Wt. of cocoon x 100

• Shape

There are different shapes of cocoons; round, oval, spherical and pointed ends, and spindle shape. Spherical egg shaped and moderately constricted cocoons are easily reelable, where as deeply constricted in the middle and cocoons with pointed ends are commercially not suitable for steady reeling.

Keeping in view of the above important characters for commercial purpose the defective cocoons such as undersized cocoons, malformed cocoons should be avoided due to the less content of silk. Immature cocoons stained cocoons and cocoons having mould should be avoided, as it is results in poor reelability and wastage due to the attack of fungus.