More than you ever wanted to know about grading jute for rope

Posted on Sat, 27 July 2013


If you are into your rope even half seriously, you will have figured by now that not all rope is equal and nor is all jute. There are a lot of variables, even assuming we are only looking at 3-ply twisted jute rope in 5-6mm. For example, there is consistency of manufacture in terms of diameter, twist, number and obviousness of yarn joins etc.

The lay (how many turns per inch/cm, like 'pitch' in relation to screws) and tightness is a key determinant of flexibility and weight. The closer and tighter the lay, the stiffer and heavier the rope will be. Loose laid ropes such as those used in Japan tend to be lighter. There is, as with most things, a trade off between lightness/flexibility and durability. Petrol-heads will be familiar with a similar situation between short-lived sticky race tyres and lower performance, but more durable, touring ones. The main problem is that loose laid ropes tend to suffer from 'high-stranding' which is where the plies go out of balance due to stretching or, most often, snagging or twisting at the bight. This means that without painstaking maintenance to re-balance the strands, it quickly becomes usable. I am delighted to say that my Tossa Lite seems to overcome this and provides a superb balance between all the desirable qualities.

We then get down to the yarn used to make the strands (plies) which will have a big influence. The finer the yarn, i.e. the thread, the smoother the rope. Conversely, the fewer, the coarser the rope. For example, a 15 yarn per ply rope is way smoother than one with 5-7.

If all these factors are equal, the final defining factor in determining what the rope will be like is the grade of fibre. After all, you can't make a silk purse from a sow's ear. This a lot more complex than might assume. For a start, there are numerous grades of the various types of jute. There follows an excellent explanation of the grading systems. Yes, not just one. Finally, yarns can even be blends of various types or grades of fibre. You really didn't expect it to be that easy, did you?

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Grading System of Jute Fiber: 

Jute fibers are graded according to three qualities of fibers. They are-
On a basis of fiber properties: I.Length
II.Strength
III.Fineness
IV.Color
V.Lusture
VI.Roots and cleanliness and uniformity in color.

On the basis of color: 
There are two colors-

  1. White and golden
  2. Brown to red corresponding to the main varieties capsularies and olitorius.

On the basis of export: 

  1. A bottom
  2. B bottom
  3. C bottom
  4. X bottom

On the basis of quality of raw jute 

  1. Pucca grading
  2. Kutcha grading

Pucca Grading:

Raw jute from which roots have been cut.White Jute: 
Bangla white special (BWS): White or creamy Finest texture Very good luster, clean, well hackled Completely free from any defects of jute Entirely free from red ends

Bangla White-A (BW-A): White to light cream Fine texture Strong and very good luster, clean Completely free from red ends and any blemish

Bangla White-B (BW-B): Light cream to straw color Good texture Strong and good luster, well hackled Free from blemish and red ends excluded .

Bangla White-C (BW-C): Light grey or light reddish to straw color Sound strength Average luster Clean but free from croppy or hard gummy Tops and roots and red soft ends are permissible.

Bangla White-D (BE-D): Any color Average strength Occasional bark and specks permissible Slightly croppy and gummy tops permissible Red ends also permissible.

Bangla White-E(BW-E): Any color Any strength but free from perished fibers Unretted jute.

Tossa Jute: 
Bangla Tossa Special (BTS): 

  • Uniform golden or reddish color
  • Finest texture
  • Very strong
  • Very good luster
  • Clean cut and well hackled
  • Completely free from any defects.

Bangla Tossa-A(BT-A): 

1 .Uniform sliver grey to golden color 

  • Fine texture
  • Strong and good luster
  • Clean cut and well hackled
  • Completely free from any blemish.

2.Uniform light golden to reddish color 

  • Fine texture
  • Strong and good luster
  • Clean cut and well hackled
  • Completely free from any blemish.

Bangla Tossa-B (BT-B): 

1.Light to medium grey color

  • Sound clean
  • Good texture
  • Average luster
  • Clean cut and well hackled
  • Free from any defects

2.Light grey or reddish excluding dark gray color 

  • Sound clean
  • Good texture
  • Average luster
  • Clean cut and well hackled
  • Free from any defects

Bangla Tossa-C (BT-C): 

  • Mixed colors
  • Average strength
  • Occasional bark and soft specks allowable
  • free from runners
  • Slightly croppy and gummy tops permissible
  • Well cut and hackled but free from black root ends.

Bangla Tossa-D(BT-D): 

  • Mixed colors
  • Average strength
  • Occasional bark and specks allowable
  • Free from runners
  • croppy and gummy tops permissible
  • Rough cut and hackled
  • Free from black root ends

Bangla Tossa-E(BT-E): 

  • Any color
  • Any strength but free from unretted jute
  • Stick and perished fibers
  • Rough cut and hackled bark and hard Centre permissible

Kutcha Grading:

Raw jute from which roots have not been cut.Kutcha bales are graded as follows-
  1. Tops
  2. Middle
  3. Bottoms
  4. B-bottoms
  5. C-bottoms
  6. X-bottoms

Tops: 

  • Very strong fiber
  • Excellent color and luster
  • Free from all defects
  • Cutting not more than (White 15% Tossa 10%)

Middle: 

  • Strong sound fibers
  • Average color and luster
  • Free from all specks runners and harsh crop end (White 25% Tossa 15%)

Bottoms: 

  • Sound fibers
  • Medium strength
  • Free from all hard centered jute (White 30% Tossa 20%)

B-bottoms: 

  • Sound fiber
  • Medium strength
  • Not suitable for higher grade(White 35% Tossa 25%)

C-bottoms: 

  • Medium strength
  • Any color
  • Free from runners and choppiness.

X-bottoms: 

  • Weak, harsh jute
  • Free from tagled jute and stick

Habijabi: 

  • Tangled jute
  • Free from any dust and cuttings

 

Classification of Jute

Classification of jute according to the quality (Geographical distribution according to Bangladesh):

  1. Jat
  2. District
  3. Northern

Jat: 

  • Jat is the finest quality jute with firm
  • It has good color and length
  • It has good luster

This type of jute fiber grows in the district of Mymensingh, Dhaka and Comilla.

Jute plant

District: 

District jute is close to Jat in quality.
  • The fiber is not uniform in textures and strands
  • Its color varies from light cream to dull grey
  • Its length is shorter.

There are two types of District jute. They are-

  1. Hard district
  2. Soft district

Hard district:

The hard district jute is better than the soft district.It mainly grows in the district of Faridpur

Soft district:

This type of jute grows in district of Noakhali,Pabna,Barisal,Jessor,Khulna,Sylhet,Lower Comilla,Chittagong and some part of Dhaka.

Northern: 

  • Northern jute is of somewhat inferior quality.
  • The fiber is dull-colored fluffy hairy and barky
  • Generally medium length and weak.

This type of jute grows in District of Rangpur, Dinajpur, Bogra and Rajshahi.

 
Jute yarn is generally available in single and multiple twists. Available in various specifications, these cater to needs of developing market. Winding in cylindrical, conical and cone less spools or hanks is done as per prerequisites of our customers. This excellent jute yarn finds extensive application in carpet industry. Now we will discuss about the types of jute yarn and batch selection technique of jute yarn.
 
Jute yarn
 
1. Hassian Warp: 
 
These types of yarn are good, clean and free from specks with high lusture. For manufacturing this type of yarn, clean and defect free jute is required. To make this type of yarn clean and defect free jute is required.

Batch Selection: 
Hard jute .......................................70%
Soft jute ........................................30%Example: For 8 lbs/spyndle hassian warp

White C........................................40%
White X ...................................... 40%
Tossa ...........................................20%

2. Hassian Weft: 

Hassian weft yarn is cleaner and softer than hassian warp yarn. So for hassian weft clean fibre is required, but fibre of lower strength can be used to hassian weft yarn.

Batch Selection:

For Heavy YarnHard jute..................................30%
Soft jute ...................................70%

For Light Yarn

Hard jute .................................50%
Soft jute ...................................50%

Example: For 8.5 lbs/spyndle hassian weft

White C ...................................40%
White X ...................................40%
Tossa ........................................20%

3. Sacking Warp: 

Sacking warp jute yarn is good and strong. Specks and colour is not important when manufacturing this type of yarn. So, 70 to 80% Tossa jute can be used.

Batch Selection: 

Hard jute ................................... 60%
Soft jute .....................................40%Example: For 8 lbs/spyndle sacking warp

X bottom ..................................67%
S M R ......................................33%

4. Sacking Weft: 

Sacking weft yarns are low quality yarn. It is coarse and is made from low grade jute fibre. It may contain line cuttings, bale cuttings, soft and hard waste, rope waste, jute dust, habijabi and entangled jute.

Example: For sacking weft

NC .......................................................70%
S M R ..................................................15%
Caddis ..................................................5%
Thread waste and gunny cuttings............10%

5. C.B.C (carpet breaking cloth):

Batch Selection: 

Hard jute ................................... 100%Example: For 8 lbs/spyndle C.B.C warp

B.W.B ....................................... 40%
B.W.C ...................................... 60%

Example: For 8 lbs/spyndle C.B.C weft

 
Reproduced from Textile Learner

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As you can see, there are almost infinite combinations which can effect how rope feels and behaves. Consequently, the quest for the perfect rope makes the search for the Holy Grail look like an Easter Egg hunt.


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