Stone wash (wet Wash)

Working Principle

The process is based on mechanical friction between denim garments, pumice stones and the rotating drum of an industrial washing machine.

1. Denim garments are loaded into a rotary washing machine with water.
2. Pumice stones, selected by size and hardness, are added to the wash bath.
3. As the drum rotates, the stones continuously rub against the surface of the garments.
4. This abrasion:
• Removes indigo dye from raised areas
• Breaks down surface fibers
• Creates contrast at seams, edges and folds
5. Once the desired appearance is achieved, the stones are removed.
6. Garments are then rinsed, softened and dried.

Resulting Effects

Stone washing leaves a very distinct signature. You can usually spot it right away.

• That vintage, faded look—not uniform, a bit random
• More defined seams and edges, almost highlighted
• Softer hand feel, less rigid than raw denim
• A naturally uneven wash effect, which actually adds character

Materials Used

Pumice Stones

• Lightweight, porous volcanic rocks.
• Sizes can vary (1–7 cm).
• Larger stones give stronger abrasion, smaller stones produce more subtle effects.

Enzymes (Bio-Stone Wash – optional)

Many manufacturers now replace stones partially or fully with cellulase enzymes, which dissolve surface fibers and reduce stone damage.

Auxiliaries

• Detergents
• Anti-back staining agents
• Buffering chemicals
• Softening agents

Stone Wash Recipe

Batch Example

• Machine Load Capacity: 300 kg
• Garment Load: 150–180 kg (50–60% loading for good tumbling)
• Liquor Ratio: 1:6 to 1:8
• Pumice Stone: 0.5–3.0 kg stones per kg garment (depending on effect)

Process	Chemical / Material	Dosage	Temperature	Time
Stone Wash	Pumice Stones	1–2 times garment weight	Room temp	30–60 min
	Detergent	0.5–1.0 g/L	Room temp
	Anti-back staining agent	0.5–1.0 g/L
Rinse 1	Water only	–	Cold	5–10 min
Rinse 2	Water only	–	Warm	5–10 min
Softening	Cationic/Silicone Softener	0.5–1.5% (owf)	25–35°C	10–20 min
Final Step	Extraction + Dry	–	As required	–

Bio–Stone Wash Recipe (Optional)

This is widely used as a greener alternative.

Process	Chemical	Dosage	Temperature	Time
Enzyme Wash	Neutral/Acid Cellulase	0.5–2% (owg)	45–55°C	20–40 min
	Anti-back staining	0.5–1.0 g/L
Rinse	Water	–	Cold	5–10 min
Softener	Silicone Softener	1–2%	30°C	15–20 min

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Stone Washing Process Flow

Step 1: Garment Loading

• Load garments at 50–60% of machine capacity to ensure good abrasion.
• Check zippers, buttons, trims for strength.

Step 2: Desizing (Optional but recommended)

• Add desizing enzyme or detergent.
• Liquor ratio: 1:8
• Temperature: 50–60°C
• Time: 10–15 min
• Drain.

Purpose: Remove starch and allow even washing.

 Step 3: Stone Washing

• Add pumice stones into the tumbler.
• Add garments and required liquor.
• Add detergents/anti-back staining chemicals.
• Run the machine:
• Temperature: 25–40°C
• Time: 30–60 min
• Speed: 15–25 rpm

Importance:
The stones create abrasion—removing dye from surface fibers and giving the faded look.

Step 4: Drain & Stone Removal

• Drain the wash water.
• Manually or mechanically separate stones from garments.
• Transfer garments to rinsing.

Note: Stone removal is labor-intensive; many factories now use synthetic stones or enzymes.

Step 5: Rinsing (1–2 cycles)

• Rinse 1: Cold water – 5 to 10 min
• Rinse 2: Warm water – 10 min

Purpose:
Remove stone dust, loose fibers and detergent residues.

Step 6: Optional Enzyme Wash

If a softer, cleaner look is required:

• Add cellulase enzyme.
• Temperature: 45–55°C
• Time: 20–40 min
• Dosage: 0.5–2% owg
• Run with gentle action.

Stops when the desired shade is achieved.
Neutralize enzyme if required.

Step 7: Softening

• Fill machine at LR 1:6
• Add softener
• Temperature: 25–35°C
• Time: 10–20 min

Softener improves hand feel and flexibility.

Step 8: Extraction

• Hydro-extract for 3–5 minutes.
• Ensure no residual stones.

Step 9: Drying

• Tumble dry at 60–75°C until fully dry
  or
• Line dry (for premium denim pieces)

Advantages, Challenges and Modern Alternatives