DENIM WASHING PROCESS

DENIM WASHING PROCESS

ABSTRACT

As denim is one of the tradition item and the denim washing have very stable performance. However, there are some of the comments that when the fabric has longer washing time, use of the chemical on the washing procedure will affect the physical performance such as the tensile strength will decrease. In order to achieve an optimum the effect of washing process on the denim woven fabric in different washing time, Enzyme Wash, Enzyme wash with bleach, Enzyme wash with stone and Enzyme wash with stone and bleach were carried out for cotton and cotton - spandex denim fabric. The effect of the washing parameters, such as the temperature, time and pH on the result of the cotton and cotton spandex denim after treatment were studied by assessment of the tensile physical properties and elongation to break

KEYWORDS: Enzyme, stone, pH, elongation to break

Origin

The word 'denim' comes from the name of a sturdy fabric called serge, originally made in Nimes, France, by the André family. Originally called Serge de Nimes, the name was soon shortened to denim. Denim has been used in America since the late 18th century. Denim was traditionally colored blue with indigo dye to make blue "jeans", though "jean" then denoted a different, lighter cotton textile; the contemporary use of jean comes from the French word for Genoa, Italy , where the first denim trousers were made

 

The history of denim

A popular conception of the entomology of the denim is that it is a contraction or derivative of the french term SERGE DE NIMES. Denim was traditionally colored blue with indigo dye to make blue “Jeans“Though “Jean“ then denoted a different , lighter cotton textile ; the contemporary use of jean comes from the French word for Genoa ,Italy,(Genes ) , from which the first denim trousers were made .Similarly woven traditional American cotton textile is the diagonal warp-striped hickory cloth that was once associated with railroad men’s overalls, in which blue or black contrasting with undyed white threads from the woven pattern . Records of a group of New Yorkers headed for the California gold fields in 1849 show that they took along four “hickory shirts “ apiece. Hickory cloth would later furnish the material for some “fatigue” pantaloons and shirts in the American civil war.

 

Objects of garments washing:

1.    To develop softness in garments: Size materials applied during manufacturing present in the fabric are removed which enhances soft hand feel . Additional softness may be attained by using softener.

2.     To introduce fading effect: Dyes or pigments are present in the fabric , used during coloration, are washed out locally or partially which result fading or worn out effects in the garments.

3.     To create new fashion: Washing Process of garments bring different outlook ( faded, color tinted etc ) thus creating new fashion for the new generation especially for teenagers.

4.    To satisfy the consumer: As the contraction or extraction (shrinkage ) occur due to washing , the wearer can use the garments after purchase satisfactory

Advantages of garments washing:

The following advantages are obtained could be gained from the garments washing—

1. Removal of starch or size materials makes the fabric soft hand feels.
2. Softness could be increased by the addition of softener just at the last stage of washing.
3. Dirt, spots, impurities, gum etc, if accumulated in the garments during manufacturing could be removed.
4. During washing shrinkage may takes place, therefore after washing there is no possibility to create such problem.
5. Washed garments could be worn directly after purchase.
6. Faded or worn out effect could introduced to the garments which creates new fashion
7. Similar outlook can be obtained by different washing techniques.
8. Comparatively lower capital is required to set up a washing plant.
9. Lower land space and least manpower cost are required to run a washing plant.

Unavoidable changes / limitations of garments washing

Like other processes the garments washing is also not without some limitations. They included as below-

1. Garments size change: Size change takes place due to shrinkage properties of fabric. The amount of shrinkage properties of fabric determines the size change of the garments.
2. Size material is partly removed: Unfixed dyes may remain on the surface of the garments and it is necessary to remove completely after washing.

TYPES OF DENIM WASH:

1. Denim washes are of following two type :–

1.               Chemical washes

2. Denim bleaching
3. Enzyme wash
4. Acid wash

2.                 Mechanical washes

5. Stone wash
6. Microsanding

v Chemical washes

1.   DENIM BLEACHING:

In the process a strong oxidative bleaching agent like sodium hypochlorite or KMnO4 is added during the washing with or without stone addition. Discoloration produced is usually more apparent depending on strength on the bleach liquor quality, temperature and treatment time. It is preferable to have strong bleach with short treatment time. Care should be taken for the bleached goods so that they should be adequately antichlor or after washed with peroxide to minimize yellowing. Materials should be carefully stored before processing for color uniformity,

 Process cycle:

Desizing

Ø  Load the garments into the washing machine (100 kg) ;

Ø  Add water (liquor ratio 1:5) and start the machine running(12-15 rpm) ;

Ø  Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;

Ø  Add detergent (1% i.e. 1kg) ;

Ø  Supply steam to raise temp.(60°C) ;

Ø  Continue the process for 20 min and then drain the liquor ;

Ø  Hot wash (at temp. of 40°C to 50°C for 5 minutes).

Bleaching

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );

Ø  Start m/c running ( 12 to 15 rpm ) and add soda ash (Na2CO3) to liquor (2% i.e. 2kg)

Ø  Add costic soda (NaOH) to liquor (2% i.e. 2kg) ;

Ø  Add bleaching chemical (H2O2) to liquor (5ml per liter, i.e. 2.5 liters) ;

Ø  Add stabilizer to liquor (2ml per liter, i.e. 1 liter) ;

Ø  Supply steam to raise temp.(70°-800C) ;

Ø  Continue the process for 60 to 70 min. and drain the liquor ;

Ø  Hot wash (at 60°C for 5 minutes).

Neutralization

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 liters );

Ø  Start m/c running ( 12 to 15 rpm );

Ø  Add acetic acid ( CH3COOH ) to liquor (1 to 2 ml per liter, i.e. 500ml to 1liter);

Ø  Continue the process for 10-15 min and then drain the liquor.

Brightening treatment

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );

Ø  Add Fluorescent Whitening agent/Fluorescent Brightening agent to liquor (% as required );

Ø  Supply steam to raise temperature (800C);

Ø  Continue the process for 10 min and then drain the liquor.

Softening

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );

Ø  Start m/c running ( 12 to 15 rpm );

Ø  Add softener to the liquor (0.1 to 0.5%, i.e. 100g to 500g);

Ø  Supply steam to raise the temperature (as required 400 to 600C );

Ø  Continue the process for 5 minutes and then drain the liquor and unload the garments.

Limitations of denim bleaching:

Ø  Process is difficult to control i.e. difficult to reach the same level of bleaching in repeated runs.

Ø  When desired level bleaching reached the time span available to stop the bleaching is very narrow. Due to harshness of chemical, it may cause damage to cellulose resulting in severe strength losses and or breaks or pinholes at the seam, pocket, etc.

Ø  Harmful to human health and causes corrosion to stainless steal.

Ø  Required antichlor treatment.

Ø  Problem of yellowing is very frequent due to residual chlorine.

Ø  Chlorinated organic substances occur as abundant products in bleaching and pass into the effluent where they cause severe environmental pollution.

 

2.   ENZYME WASH

It is environmentally friendly wash. It involves the application of organic enzymes that eat away at the fabric, i.e. the cellulose. When the desired color is achieved, the enzyme can be stopped by changing the alkalinity of the bath or its temperature. Post treatment includes final ringing and softening cycle.

 The effects produced by cellulose enzyme are :—-

Ø  Use of cellulose making the seams, hems, and pockets more noticeable;

Ø  Salt paper effect is color contrast effect.

Ø  Faded garment washed with acid cellulose enzyme provides less color contrast in proportion to garment washed neutral cellulose enzymes.

Ø  Garment load size of the m/c is 35-40 jeans per m/c and it cannot be overloaded.

3.   ACID WASH

It is done by tumbling the garments with pumice stones presoaked in a solution of sodium hypochlorite or potassium permanganate for localized bleaching resulting in a non uniform sharp blue/white contrast. In this wash the color contrast of the denim fabric can be enhanced by optical brightening. The advantage of this process is that it saves water as addition of water is not required.It consists of soaking pumice stones with chlorine and using their abrasive power to bleach jeans into sharp contrasts. Also known as moon, fog, marble, ice and frosted.

  

Process cycle :

Desizing

Ø  Load the garments into the washing machine (100 kg) ;

Ø  Add water into the machine(1:5 liquor ratio i;e. 500 liters) ;

Ø  Start machine running (12 to 15 rpm) ;

Ø  Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;

Ø  Add detergent (1% i.e. 1kg) ;

Ø  Supply steam to raise temp.(60°C) ;

Ø  Continue the process for 20 min and then drain the liquor ;

Ø  Hot wash at temp. of 40°C to 50°C for 5 minutes.

 Bleaching

To carry out the Bleaching process, the following two steps are to be passed over :

Step  1.

Ø  Take stone of some volume of the volume of garments ;

Ø  Soak the sfone with the following chemical solution for 2 to 3 minutes ;

Ø  Water 100 litres

Ø  Potassium permanganate 1 kg

Ø  Phosphoric acid 300 ml (3ml per litres)

Ø  Here the porous of stones are dried in the open air for 60 to 90 min.

Step  2.

Ø  Load the garments treated in step # 1 and step # 2 in a dry m/c. Lot size should be 20 to 30kg.

Ø  Run the m/c for 5 to 7 minutes. Due to the rotation of m/c the socked stones will hit the garments surfaces and the chemicals in the stone will destroy color of the fabric. Multilayer fabric areas like collar, cuff, pocket, pocket side seam etc. area will be brushed more than the single layer areas, therefore more fading effect will be produced in those areas resulting new color effect in the garments.

Ø  Unload the garments and separate the stones from the batch.

Ø  In this stage KMnO4 and H3PO4 reacts with each other and gives Oxygen which oxidize the color. Here a byproduct MnO2 is produced which should be neutralized.

Ø  6KMnO4 + 4H3PO4 = 2K3PO4 + Mn3(PO4)2 + 6H2O + 3MnO2 + 2O2

Ø  This MnO2 is solubilized by Sodium Metabisulfite (Na2S2O5).

Ø  Na2S2O5 + H2O = 2NaHSO3

Ø  NaHSO3 + MnO2 = MnSO4 + NaOH

Ø  Load the garments to the m/c ;

Ø  Add water into the m/c (1:5 liquor ratio, i.e. 500 litres) ;

Ø  Continue the process (12 to 15 rpm) ;

Ø  Add sodium metabisulfite (1 to 2 gpl, i.e. 500 g to 1kg) ;

Ø  Continue the process for 5 to 10 min and then drain the liquor ;

Ø  Hot wash (at 40o to 50o C for 5 minutes).

Nutralization

Ø  Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );

Ø  Start m/c running ( 12 to 15 rpm );

Ø  Add acetic acid ( CH3COOH ) to liquor (1 to 2 ml per liter, i.e. 500ml to 1liter);

Ø  Continue the process for 10-12 min and then drain the liquor.

(To be Continued in November 2013 issue)

Magazine Article :DYE CHEM PHARMA (October  2013)

Water Jet Cutting Machine

Water Jet Cutting Machine

v  Water jet Cutting Machine:

A water jet cutter is an industrial tool capable of cutting a wide variety of materials using a very high-pressure jet of water or a mixture of water. The cutter is commonly connected to a high-pressure water pump where the water is then ejected from the nozzle, cutting through the material by spraying it with the jet of high-speed water. The features of water jet cutting machine is given below: 

v  Features of Water-jet Cutting Machine:

1.    In water jet cutter, water or mixture of water is used to cut fabric which is controlled by computer.

2.    Special software is used to cut fabric.

3.    A very high velocity (60,000 lb/ square inch) & small diameter steam of water is created by a water jet intensifier pump.

4.    The high pressure jet acts as a solid tool & sharp knife which can easily cut the fabrics, lathers & plastic materials.

5.    As the jet penetrates successive plies in a spread, the momentum decreases & cutting ability is reduced. So, the lower lays of fabric cutting will be wide & less effective.

6.    The jet of water & loose fibers normally caught & drains away by a catcher when cut the fabric. It is in the bottom of the fabric lays & moves with the same speed & the same direction of water jet.

7.    To improve the cutting speed, it is needed to adjust the pressure & radius of the jet. 

v  Advantage of Water-jet Cutting Machine:

1. Most effective to cut hard materials such as leather & plastic.
2. Sound of cutting is less.
3. Excess heat is not produce.
4. Higher cutting speed.
5. The table is not cut as catcher is used.
6. Since there is no solid knife so, no sharpening is required.

v  Disadvantage of Water-jet Cutting Machine:

1.    There is a danger of wet edges.

2.    Water spot may occur on fabric.

3.    High costly.

4.    Hard water causes rusting. So water must be filtered & de-ionized before use.

5.    As in the lower lay, water jet spreads out & then cut is wider & rough at the bottom of the spread.

6.    Not suitable for high lay of fabric.

7.    The sound of jet need to control.

v  Uses/Application of Water-jet Cutting Machine: 

Water jet machine is widely used to cut metal, composite, marble, granite, ceramic tile, glass, cloth, food, leather, rubber, nylon, wood, dynamite and so on. Water jet cutter is not suitable for cutting fabric but this cutter is under research to cut fabric. 

References: 

1. Garment & Technology-Prof. M.A. Kashem
2. Garments Manufacturing Technology- Saiful Azam, Abu Saleh.
3. http://en.wikipedia.org/wiki/Water_jet_cutter
4. http://www.jetedge.com/
5. http://www.wardjet.com/

ONLINE ARTICLE: http://textilecentre.blogspot.in/2013/09/water-jet-cutting-machine.html

Stitches Per Inch (SPI)

Stitches Per Inch (SPI)

Introduction 
When writing garment specifications, you should not neglect specifying the proper number of stitches per inch that should be used in your sewn products. Why? Because the number of stitches per inch can have a direct influence on the following:

1. the seam strength;
2. the stitch appearance;and
3. the seam elasticity on stretch fabrics.

An estimated seam strength formula was developed years ago for woven seams where one piece of fabric is placed on top of another with a specific seam margin and stitched with either a 301 lockstitch or 401 chain stitch.

Obviously, the seam strength is dependent on a number of factors including:

1. Type & Weight of the Fabric
2. Stitch & Seam Construction
3. Stitches Per Inch
4. Thread Type and Size
5. Stitch Balance (Thread Tensioning)

Formula for Estimating Seam Strength on Woven Fabrics 

301 Lockstitch - Estimated Seam Strength 
= SPI X Thread Strength (lbs.) X 1.5* 

* 1.5 is a factor based on the average loop strength ratio of most sewing threads. 
= 10 SPI X 4.0 lbs. X 1.5 = 60 lb. strength 

401 Chainstitch – Estimated Seam Strength 
= SPI X Thread Strength (lbs.) X 1.7 * 

* This factor is higher than a lockstitch because almost twice as much thread is consumed per inch of seam using a chainstitch. 
= 10 SPI X 4.0 lbs. X 1.7 = 68 lb. strength 

From this formula, you can see the impact that stitches per inch, thread strength and stitch selectionhave on the strength of the seam. Generally, the more stitches per inch, the greater the seamstrength. There are rare cases where adding stitches per inch can actually damage the fabric so thatthe seam is weakened, however, this only happens on specific fabrics that can be damaged by excessive needle penetrations. 

Given:

• 301 Lockstitch Superimposed Seam
• Thread Used Top & Bottom = T-24 Perma Core – Strength: 2.6 lbs.

SPI	6	8	10	12
Estimated Seam Strength	23.4 lbs	31.2 lbs	39 lbs	46.8 lbs

As you can see from the chart above, the stitches per inch has a tremendous impact on the strength of the seam, as long as the fabric doesn’t rupture before the thread. If the same seams were sewn with a lower tenacity spun polyester thread, this also will effect the resulting seam strength. 

Given:

• 301 Lockstitch Superimposed Seam
• Thread Used Top & Bottom = T-27 Spun Poly – Strength: 2.2 lbs.

SPI	6	8	10	12
Estimated Seam Strength	20 lbs	26 lbs	33 lbs	40 lbs

Some manufacturers substitute a smaller bobbin thread when sewing lockstitch seams to minimize the number of times it takes the sewing operator to change the bobbin. Remember, however, that the resulting seam strength will be much less and will be determined by the strength of the bobbin thread and not the needle thread. 

How to Measure the Stitch Length or Stitches Per Inch? 
The stitch length is measured by measuring the number of lengths of thread found within Two inch.Stitch counters are available from A&E that make this measurement easier, however, you can place a ruler next to the seam and perform the same task. 

SPI is measured by counting the number of lengths of thread found within Two inch. As you can see here, there are approximately 10 SPI sewn in this seam

SPI Recommendations for Wovens & Knits 
Below is a list of garments and the typical number of Stitches Per Inch recommended for each of them. 

WOVEN GARMENTS 

Garments	SPI	Comments	Garments	SPI	Comments
Denim Jeans, Jackets, Skirts	7 – 8	Fewer stitches per inch generally will give a more contrast stitchappearance.	Childrenswear	8 - 10	Usually 8 to 10 spi is adequate to provide adequate seam strength and at the same timeallow for quicker cycle times.
Twill Pants or Shorts	8 – 10	More stitches per inch will help minimize seam grinning.	Dresses, Skirts	10-12	Due to many of the operations being lockstitch, usually 10 – 12 spi is required to provide adequate seam strength.
Trousers, Dress Pants, Slacks	10-12	On some operations like serge panels, it may be desirable to use a longer stitch length.	Blindstitch Operations on Slacks,Dresses Skirts, etc.	3-5	A long stitch length is desirable to minimize the dimple or appearance of the needle penetration on the outside of the garment.
Dress Shirt or Blouse	14-20	Using more SPI llows the use of smaller diameter threads that will minimize seam puckering.	Buttonsew (4 hole button)	16	Buttonsew machines are cycle machines with a predetermined number of stitches per cycle.
Casual Shirts, Blouses, Tops	10-14	Using more SPI will give more of a tailored stitch appearance and better seam coverage when serging.	Buttonhole (1/2” purl or whip stitch)	85-90	Generally sewn vertically – approx. 85- 90 stitches with a lockstitch buttonhole machine.

When setting standards for stitches per inch, you should always keep in mind that more stitches per inch used in a seam requires longer sewing cycles to complete the seam. Longer sewing cycles translates in to higher labor costs and lower production levels. A sewing machine sewing at 5,000 SPM (stitches per minute) at 8 SPI will sew 17.4 yards of seam per minute. A sewing machine sewing at 5,000 SPM at 14 SPI will sew 9.9 yards of seam per minute. 

More stitches per inch will also consume for thread per inch of seam. This will contribute to higher seam strength and more elastic seams, but will also increase the consumption of thread required to sew the garment. 

Therefore, the recommendations listed above are common stitch levels that provide adequate seam strength but also take into consideration the factors just mentioned. 

When sewing knit fabrics, you should always check for excessive “seam grinning” of the seam; and also check for “stitch cracking”. “Seam grinning” occurs when thread stitch balance is too loose allowing the seam to open up too much when stress is applied to it. “Stitch Cracking” is checked by applying pressure on the seam in the stitching direction. If the thread tensions are too tight or if you are not using enough stitches per inch, the threads will rupture as stress is applied on the seam. Therefore, the following recommendations have been made for the number of stitches per inch to be used on the following garments. 

KNIT GARMENTS 

Garments	SPI	Comments	Garments	SPI	Comments
Jersey T-shirts, Tops, Polos	10-12	Using more SPI increases the chance of needle cutting.	Swimwear	12 - 16	The more elastic the seam, the more SPI that should be used to minimize stitch cracking.
Underwear	12-14	The more elastic the seam, the more SPI that should be used to minimize stitch cracking.	Dresses, Skirts	10 - 12	The more elastic the seam, the more SPI that should be used to minimize stitch cracking.
In fantwear	10-12	The more elastic the seam, the more SPI that should be used to minimize stitch cracking.	Intimates	12 -16	The more elastic the seam, the more SPI that should be used to minimize stitch cracking.
Fleece	10-12	More stitches per inch are required to provide the proper seam coverage on fleece.	Stretch Knits (Lycra®, Spandex®, etc.)	14-18	More stitches per inch are required to provide the proper seam coverage on fleece.
Sweaters (Med. To Hvy.)	8-10	The more elastic the seam, the more SPI that should be used to minimize stitch cracking.	Hosiery, Socks	35-50	Usually sewn with very fine thread. More spi are required to minimize seam grinning and seam elasticity.

Conclusion:
From the comments and information listed above, you can see how important adding specifications for Stitches Per Inch to your garment specification instructions. Using the correct number of stitches per inch can greatly enhance the strength, appearance and performance of the seam for a given fabric type and application. 

References: 

1. Overview of fashion - By Prasad Kulkarni 

ONLINE ARTICLE: http://textilelearner.blogspot.com/2013/08/stitches-per-inch-spi-how-to-measure.html
                          http://www.fibre2fashion.com/industry-article/50/4930/stitches-per-inch1.asp