Stone Wash Process of Garment | Stonewash with Chlorine

Last Updated on 22/08/2021

Garment Stone Wash:
In order to accelerate the garment wash effect and to give garments an even more unique appearance and softer hand, abrasive stones were introduced to the wash bath. Stone washing is the most important process, and it has innumerable variants now. To get a faded and worn-out look on the garment stone wash is done. A variety of natural and synthetic stones are available for stonewashing with perhaps the most widely used being pumice or volcanic rock. As the stones are used, they slowly disintegrate, reducing the severity of the stonewash effect over a period of time. The stones not only abrade the fabric but also gradually abrade the inside of the rotary drum. A machine used for stonewashing should not be used to dye delicate articles or when abrasion would be detrimental to the fabric.

As the popularity of prewashed garments grew, the idea of using abrasive stones to accelerate the color fading process was developed and ‘stone washing’ became the evolution. Pumice stones were included in the washing process, or tumbled with the damp garments to wear down the stiffest portions, for example, belt areas, cuffs and pockets.

Volcanic rocks or pumice stones are added during washing as abradants. The color fading is more apparent but less uniform. The degree of color fading depends on the washing time (60–120 min), stone ratio (weight of stones relative to weight of the garment) (0.5: 1–3:1), size of stones (diameter: 1–7 cm), liquor ratio (∼10:1) and garment load. The world’s major pumice stone supplying countries include the USA, Turkey, Italy, Germany, Iceland, New Zealand, Japan, Indonesia and Philippines. The basic steps of denim stone washing are as follows:

Desizing (10–15 min) → Rinsing → Stone washing → Rinsing (with perborate and optical brightener if necessary) → Softening.

Objectives of Stone Wash:

1. To create or produce irregular fading or old looking affect on garments.
2. To remove dust, oil spot, impurities from the garments.
3. For soft felling to wear the garments i.e; to improve softness.
4. To achieve the buyer washing standard.

Factors of Stone Wash:
Stone wash depends on some factors. They are given below:

1. Effect of stone ratio:
Figure 2 shows that with stone ratio below 0.5:1, no significant color fading effect in the denim garments is noted. When the stone ratio is high, the color fading effect becomes enhanced. However, too high a stone ratio may cause severe abrasion leading to fabric damage .

2. Effect of stone size:
Figure 3 shows the effect of stone size on the color fading effect. It is noted that the smaller the stone size, the better is the color fading effect. In addition, small stones can provide an even and uniform abrasion effect, but the color contrast produced is not good when compared with large stones.

3. Effect of stone washing time:
Figure 4 shows the color fading effect under the influence of stone washing time. It is shown that after 90 min, there is no further increase in the color fading in denim garments. Stone washing of denim fabric with pumice stones has some disadvantages and limitations, such as:

• Stones may cause wear and tear of the fabric and may damage the washing machine from abrasion of the stone with fabric or machinery parts.
• It may also create the problem of environmental disposition of waste of the grit produced by the stones.
• Increase the labour cost required to remove stone dust from finished garments. Denim garments are required to be washed several times for complete removal of the stones.
• The stone washing process may cause back staining and redeposition.
• The process is nonselective.
• Metal buttons and rivets in the garments as well as the drum of the washing machine sometimes get abraded which substantially reduces the quality of the garment and the life of the equipment.

Procedure of Garment Stone Wash:

1. Load stones into machine.
2. Load garments into machine (ratio usually 0.5 – 3.0 part weight stones: 1 part weight garments).
3. Desize with alpha amylase enzyme and detergent. Liquor ratio approximately 5-8:1.
4. Rinse.
5. Refill and tumble with stones 30 to 90 minutes, depending upon desired effect. Liquor ratio 5-8:1 at 50-70^◦C. Scouring additives can also be used.
6. Drain. Separate garments from stones (garments can be transferred to another machine).
7. Rinse.
8. Apply softener (garments can be transferred to another machine for softening).
9. Extract and unload.
10. De-stone and tumble dry.
11. Press, if required.

Softeners and/or lubricants can be added during steps three and five to reduce creasing potential. Steps 8, 9, and 10 may vary depending upon individual mill arrangement.

Stonewash with Chlorine:
By incorporating chlorine in the stonewash procedure, a color reduction of the indigo (or other chlorine sensitive dyestuff) is obtained. It is very important that any residual chlorine be removed before drying to prevent fiber degradation. This is accomplished by using an antichlor step with sodium bisulfite or hydrogen peroxide.

Working Procedure:

1. Load stones into machine.
2. Load garments into machine (ratio usually 0.5 – 3.0 part weight stones:1 part garments).
3. Desize with alpha amylase enzyme and detergent (liquor ratio approximately 10:1).
4. Rinse.
5. *Refill and add sodium or calcium hypochlorite.
6. Heat to 55^◦C.
7. Tumble 15 minutes.
8. Add second portion of sodium or calcium hypochlorite.
9. Tumble 15 minutes, maintaining temperature of 55^◦C.
10. Drain.
11. Rinse well.
12. Antichlor with sodium bisulfite or hydrogen peroxide.
13. Drain. Separate garments from stones (garments can be transferred to another machine).
14. Rinse well.
15. Apply softener.
16. Extract and unload.
17. De-stone and tumble dry.
18. Press, if required.

*Amount of sodium or calcium hypochlorite required will vary depending upon desired level of bleach down and the sensitivity of the color to chlorine. Each addition can range from 0.075% to 0.225% available chlorine. pH should be kept above 9.0, preferably 10.5-11.0. This is accomplished with the addition of soda ash with each addition of hypochlorite.

Pumice Stone Wash:
Pumice has been used since the introduction of stonewashed jeans in the early 1980s. The jeans are washed with oval or round pumice stones which should all roughly have the same format. The pumice stones are very light with a rough surface. Freshly-dyed jeans are loaded into large washing machines and tumbled with stones. Adding pumice stones gives the additional effect of a faded or worn look. The pumice abrades the surface of the jeans like sandpaper, removing some dye particles from the surfaces of the yarn. In stone-washing, stones and denim are spun together in large industrial washing machines. The longer they are spun together, lighter is the color of the fabric with better contrasts. The time duration of this procedure is set beforehand to avoid the tear and wear of the fabric. Thereafter, the fabric undergoes various processes of rinsing, softening and finally tumble-drying. These stone-washed fabrics are used for different purposes like garment making as well as for upholstery purpose.

Disadvantages of pumice stone usage:
Stone-washing the denim with pumice stones has some disadvantages. The stones could cause wear and tear of the fabric. It creates the problem of environmental disposition of waste of the grit produced by the stones. High labor costs are to be borne as the pumice stones and their dust particles produced are to be physically removed from the pockets of the garments and machines by the laborers. Denim is required to be washed several times in order to completely get rid of the stones. The process of stone-washing also harms big, expensive laundry machines.

The quality of the abrasion process is difficult to control: Too little will not give the desired look. Too much can damage the fabric, particularly at the hems and waistbands. The outcome of a load of jeans is never uniform, with a significant percentage always getting ruined by too much abrasion. The process is also nonselective. Everything in the washing machines gets abraded, including the metal buttons and rivets on the jeans as well as the drum of the washing machine. This substantially reduces the quality of the products as well as the life of the equipment and increases production costs. During the washing process, these stones will scrape off a thin layer of the denim, thus showing some of the white threads from the part of the cloth where the indigo dyeing stuff is not able to penetrate. It also creates the effect called brilliance. One may also encounter words like deep stone or super stone wash, which are an indication of how long the jeans have been stone-washed.

References:

1. Denim: Manufacture, Finishing and Applications Edited by Roshan Paul
2. Handbook of Value Addition Processes for Fabrics By B. Purushothama
3. Sustainability in Denim Edited by Subramanian Senthilkannan Muthu
4. Chemical Technology in the Pre-Treatment Processes of Textiles by S. R. Karmakar
5. Chemistry of the Textile Industry By C. Carr

Mazharul Islam Kiron

Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.

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