Textile Drying

Textile Drying

Drying happens when liquid is vaporized from a product by the application of heat. Heat may be supplied by convection (direct dryers), by conduction (contact or indirect dryers), radiation or  by placing the wet  material in a  microwave or radio frequency electromagnetic field. Over 85 percent of industrial dryers are of the convective type with hot air or direct combustion gases as the drying medium. Over 99 percent of the applications involve removal of water.

This is one of  the most  energy-intensive unit  operations due to the high latent  heat  of vaporization and the inherent inefficiency of using hot air as the (most common) drying medium.

Drying Curve

The figure above is a typical curve, in the initial period, drying rate is high; later, drying rate decrease because of interference of free moisture on the surface of the product.

Type of Dryers

1.       Hot Air Dryer- Stentor

Fabric drying is usually carried out  on either drying cylinders (intermediate drying) or on stenters (final drying). Drying cylinders are basically a series of steam-heated drums over which the fabric passes. It has the drawback of pulling the fabric and effectively reducing its width. For this reason it tends to be used for intermediate drying.  The stenter is a gas fired oven, with the fabric passing through on a chain drive, held in place by either clips or pins. Air is circulated above and below the fabric, before being exhausted to atmosphere. As well as for drying processes, the stenter is used for pulling fabric to width, chemical finishing and heat setting and curing. 

  

Contact Drying- Steam Cylinders/Cans

This is the simplest  and cheapest  mode of  drying woven fabrics. It  is mainly used for intermediate drying rather than final drying (since there is no means of controlling fabric width) and for predrying prior to stentering. Fabric is passed around a series of steam heated cylinders using steam at pressures varying from 35 psi to 65 psi. Cylinders can be used to dry down a wide range of fabrics, but it does give a finish similar to an iron and is therefore unsuitable where a surface effect is present or required

Source (Text and Images)

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Sari Weaving Techniques on Handloom

Unnati Silks have uploaded some stunning videos depicting the handloom weaving techniques in Saris. The same came be viewed here.

The following is just one of the videos showing weaving of Kanchipuram Sari.



The following Techniques of Sari Weaving are covered:

1. Kanchipuram
2. Pochampalli
3. Siddipet
4. Gadwal
5. Narayanpet
6. Ellampillai
7. Managalgiri
8. Bannerugatta
9. Dharmavaram
10. Uppada
11. Venkatgiri
12. Maheshwar
13. Rasipuram
14. Kaithoon Kota
15. Chirala
16. Kondalmpatti
17. Arni
18. Varanasi

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Process of Batik

The word batik has been derived from the word "Ambatik" which translates as "Cloth with little dots".

An amazing video has been uploaded by Moda to depict the process of Batik as practiced in South Asian country. The process is painstakingly long and involves several processes of dyeing, applying wax, washing and drying. Briefly the process involves the following stages:

1. First of all the fabric is dyed with base color.

2. Then base color combination is applied on the fabric with the help of sponge.

3. Then the fabric is dried in the sunshine.

4. Soda is sprinkled on the fabric while it is drying to get the salt effect.

5. The fabric is then covered with wax using copper stamps on wooden blocks.

6. Then the first color combination is removed from the fabric by dipping it into a solution.

7. The fabric is then made wet and put onto a flat surface.

8. Second color combination is then prepared and applied on the fabric with the help of a sponge, the fabric is crinkled carefully before this application.

9. Again the fabric is kept for drying and soda is sprinkled on it to get the salt effect.

10. Then it is dried in the sunshine by hanging.

11. The fabric is then dyed in water glass ( A solution of sodium or potassium silicate, it solidifies on exposure to air and is used to make silica gel). Until it is applied the batik colors are water soluble. Water glass fixes all the colors.

12. Then it is washed with water twice.

13. Then it is subjected to boiling to remove the wax that covered the first color combination.

14. Then it is washed with water and dried to get the final finished fabric.

You can watch the video here:


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Cost of Fashion

Just stumbled upon a few reports on the condition of women working in textile mills in South India. The reports called "Maid in India" and "Captured by Cotton" depict vividly the plight of women enrolled under the Sumangali Schemes of various Textile Mills.

The reports go to show the low cost fashion available in high streets which can be due to the conditions under which workers work in textile and garment factories.

There is another report depicting the prevalence of child labour in the sequin units in Tuglakabad and Sangam Vihar district of Delhi and how the laws are flouted by bribing off the officials.

Some eye-opening articles, I must say.

Here are the links:

1. Maid in India
2. Captured by Cotton 
3. Slavery on the High Streets

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