Singeing | Types of Singeing process | Application of Singeing in the textiles dyeing industry

Introduction: Singeing is a process, where loose hairy fibers are protruded from the surface of the cloth, fabric, and the yarn is removed by burning.

Lose fibers protruding on the surface of textile products are chanted to remove them in the textile industry. This results in higher wet ability, better dyeing properties, enhanced reflection, no "frosty" appearance, a softer surface, good printing clarity, increased visibility of the fabric structure, less pilling and reduced contamination by removing fluff and lint.

Usually, the mechanism is to pass one or both sides of fabric over a gas flame to burn off the protruding fibers. Other methods include infrared or heat for thermoplastic fibers. The singeing of yarns is called "gassing." It's usually the first step after weaving or knitting.

Objectives of Singeing:

1. To remove the short fibers from the textile materials (yarn and fabric).
2. To make the textile materials smooth, even and clean looking.
3. To develop maximum luster in the textile materials.
4. To make the textile materials suitable for subsequent next process. 

Singeing Process

Types of machine used in the singeing process: 

1. Plate singeing M/C.
2. Roller singeing M/C.
3. Gas Flame singeing M/C

Precaution takes before singeing: 

• The singeing fabric should be dry as wet fabric tends to scorch faster than dry. Upon completion of the fabric, uneven singeing may cause streaks on the fabric or bubbles. 
• Incorrect singeing can result in a loss of 75 percent in tensile strength loss in the direction of the warp. 
• The fabric should not contain any acid releasing salt that may release acid when heated and make the fabric tender. It should be avoided to stop the machines. 
• The temperature should be properly controlled otherwise thermal damage to sensitive fabrics may occur. Consideration must be given to the burning characteristics of fibers when applying this process as heat-sensitive fibers melt, forming small balls on the fabric surface. 
• These balls interfere with the absorption of dye so that after dyeing or printing, heat-sensitive fibers are generally singed.

Plate singeing process: 

• The cloth goes over and over with one or two heated curved copper panels in this type of singeing machine. 
• The plate thickness varies between 1 and 2 inches. Suitable combustion of gas mixed with air is used to heat the plates. 
• The plates are heated to light redness and the cloth fills the plates at speed from 155 to 260 meters per minute and is in contact with it. 

Plate Singeing machine process diagram 

Roller singeing process: 

• The cloth moves through and into contact with a heated cylindrical cylinder made of copper or cast iron with this kind of singeing machine. 
• With internal firing, the rotary cylinders turn slowly, and a cool surface of the roller constantly comes into contact with the cloth. 
• The cylinder rotating direction is contrary to the fabric direction so that the fibers or nap outstanding in the fabric can be lifted. This type of machine is especially suitable for velvet and other pile fabrics to be singed.

Roller Singeing machine diagram

Gas flame singeing process: 

• A suitable mixture of gas and air under pressure is used as the source of heat in gas singeing. This mixture is fed into a combustion slot burner. It is possible to use coal gas, petrol gas or butane gas as fuel. 
• The burner width can be adjusted to suit different widths of the fabric. For different fabrics, the flame height and consequently the heat intensity can be varied by changing the mixture pressure or the mixture gas and air ratio. 
• The flame temperature may reach 1300 ° C when combusted. 
• Before singing, it is important to preheat the cloth to reduce its moisture content as a dry cloth is better than a cold fabric. The heat energy can convert the moisture in the fabric into steam that can impede the singeing process. 
• The cloth may be lifted in an aqueous bath immediately after the singeing to quench any similar spark to prevent a potential fire.

Gas singeing process diagram

Advantages of Singeing:

1. Extra loose fiber can be removed
2. Smooth and even surface of fiber and fabric can be achieved.
3. In the case of singed fabrics, risk of pilling, especially with synthetics and their blends, is reduced.
4. The singed fabric allows more luster and details of the dyeing and printing color.
5. It gives very clean and shiny looks in the fabric.

Disadvantages of Singeing:

1. Once the fabric is dyed, the uneven singeing effect may cause streaks, or bubbles when the fabric is finished. 
2. Singeing is done on a gray cloth in the cotton system, but for blended fabrics containing synthetic fibers, it is not advisable to singe gray as small globules of melted synthetic fibers preferably absorb the dye, giving the cloth a skewed appearance. 
3. Thermal damage to temperature-sensitive fibers, such as polyester, may occur. 
4. Heat can cause color loss from the polyester portion of the blend due to dye sublimation when singeing is done after dyeing. 
5. The tear strength may be reduced due to over-singeing of the fabric.

The difference between Plate, Roller, and Gas singeing Processes:  The difference between Plate, Roller, and Gas singeing Processes is given below;

Plate Singeing Process	Roller Singeing Process	Gas Singeing Process
One side of fabric can be singed.	One side of fabric can be singed	Both side of fabric can be singed
Uniform temperature cannot be maintained.	Uniform temperature cannot be maintained	Uniform temperature can be maintained
Extra luster is produced due to friction between fabric and surface.	Extra luster is produced due to friction between fabric and surface.	No Extra luster is produced
Not suitable for dyeing and printing.	Not suitable for dyeing and printing.	Very suitable for dyeing and printing.
The brush is not used for proper singeing.	The brush is not used for proper singeing.	The brush is used for proper singeing.

Singeing is the first pre-treatment process of textile wet processing technology. It helps to remove short loose fiber from the fabric and yarn. This is a mechanical process of reducing pilling and short fiber. It has plenty number of advantages as well as disadvantages. 

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References:

1. "General knowledge in Textiles and Garments" by Dr. M A Sayed.

2. https://en.wikipedia.org/wiki/Singe

3. http://www.definetextile.com/2013/05/singeing.html
4. https://www.slideshare.net/skraju231/singeing-74151579
5. "Introduction to Textile Engineering" by Md. Sajjak Hossain.