Acid Stone Washing | Flow chart of Acid Stone Washing | How to apply Acid Stone washing technique in the washing plant

Introduction: Acid Stonewash is usually done with heavy cloths such as denim, canvas, and twill. Pumice stones are used during acid washing. The irregular declining effect on the surface of garments is the action of pumice stones. The pumice stones act on the surface of the garments.

Nowadays, mode without denim is incomplete. Various types of washing process are done to change the look of denim or jeans. Acid washing is the most popular among diverse denim washing processes.

Chemical used in acid stonewash: In the acid stone wash, both chemical and physical washing technique is used. There are some chemical uses for acid stone;

1. Desizing agent: Desizing agent is used primarily in the desizing process to eliminate starches, waxes, pectin fats, oil, spot and unfixed dye from denim, twills, poplin and canvas fabrics.
2. Detergent: Detergent is broadly applicable in the continuous and discontinuous pre-treatment of all fiber types and their blends. It usually applies to eliminate impurities, contamination of mineral oil and sizes from the garments.
3. Potassium permanganate(PP): Potassium permanganate is used for color out of the garments in the acid wash with the pumice stone. It is also used by the nozzle to spray the chamber from the garments for color out (whitish effect).
4. Sodium Metabisulphite: To neutralize the garment from potassium permanganate, sodium metabisulphite is used in the washing plant.
5. Acetic acid (CH3COOH): Acetic Acid is used to neutralize the garments from the alkaline condition and to control the pH value in the wash bath.
6. Softner: Softener is used to make the garments treated textiles a surface feel that is both sickly and soft and also provides excellent lubricating properties. Flax softener (cationic or nonionic) diluted with hot water then use in the machine.

Acid Stone Wash

Flow Chart of Acid Stonewash:

Batching

↓

Loading

↓

Desizing

↓

Stone Preparation

↓

Acid Wash

↓

Neutralization

↓

Softening

↓

Hydro Extracting

↓

Drying

↓

Delivery

Process of Acid Stonewash:

1. Batching: Batching is the method to get prepared the garments which will be washed and processed for a specific lot of a specific order.

2. Loading: Loading is the work where how many pieces garments will be washed is ready and load it to the machine.

3. Desizing: Desizing is an important stage of all textile processing in which' size material ' is removed from the fabric or garment before the pre-treatment process is completed, which is necessary before garment wash or other textile processes. Here, we add desizing agent and detergent for cleaning and removing size material.

• Lot weight (100 pes) = 70 kg denim long pant.
• Add water: L: R = 1: 10, 700 liter.
• Machine Running.
• Temperature: raise 60°c.
• Add Desizing agent: 1 gm / liter, 700 gm.
• Add Detergent: 1 gm / liter, 700 gm.
• Time: Run machine 15-20 minute.
• Drop the liquor.
• Rinse one for 3 minutes (cold).

4. Stone Preparation: In the acid stone denim washing process, a special type of pumice stone is used. Before use pumice stone in the wash, it required pretreatment. This will do another machine to mix the pumice stone perfectly with Potassium permanganate and Phosphoric Acid. Then it put in the open air for sometimes.

• Water: 100 L
• Potassium per manganate: 1000 Gms.
• Phosphoric Acid: 250 Gms.

5. Acid Wash: After soaking the stone in the chemical solution, the stone is load with the washing machine and also load the denim garment in the machine. Now it times to the start machine. Keep running the machine for 10-15 minute and check the garment for proper wash shade. Here the shade coming from the abrasion of pumice stone which is soaked in acid solution. The stone touches the surface of denim garment and creates an irregular faded effect. When we get the desired effect, the garment unloaded from the machine.

• Lot weight (100 ps) = 70 kg denim long pant.
• Load pumice stone in the machine.
• Load garment in the machine.
• Running the machine 10-15 minute.
• Check garment.
• Unload garment from the machine. 

6. Cleaning garment: In this step, the washed garment needs to clean. Because of the breaking small particle of the pumice stone can be there that why cleaning is required.

• Lot weight (100 pes) = 70 kg denim long pant.
• Add water: L: R = 1: 7, 490 liter.
• Machine Running.
• Add Detergent: 1 gm / liter, 490 gm.
• Temperature: raise 40-50°c.
• Time: Run the machine for 10 minutes.
• Drop the liquor.

7. Neutralization process: Now all this garment require to neutralize by Sodium Metabisulphite.

• Lot weight (100 pes) = 70 kg denim long pant.
• Add water: L: R = 1: 7, 490 liter.
• Machine Running.
• Add Sodium Metabisulphite: 5 gm / liter, 2450 gm.
• Temperature: Cold / Normal.
• Time: Run the machine for 5 minutes.
• Drop the liquor.

8. Softening: Softening is done for giving the soft and comfortable hand feel. Cationic softener use in this process and acetic acid added for neutralizing the garment from this alkaline solution. 

• Add water L: R = 1: 8, 560 liters.
• Machine running.
• Add Acetic acid 0.6 gm/liter, 336 gm.
• Add Softner 1 gm/liter, 560 gm.
• Unload the garments.

9. Hydro extracting: To remove excess water from the garment by using hydro extractor machine.

10. Drying: After hydro-extraction the garments are sent to drying machine for complete drying.

11. Quality check & Delivery: After drying the garments go to quality checking and rectify washing fault and then good one delivery.

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References:

1. "Effective Mechanical and Chemical Washing Process in Garment Industries" by Monoroma Hossain, American Journal of Applied Physics 2017, 2:1-25.
2. https://en.wikipedia.org/wiki/Stone_washing.