New denim is stiff, dark and flat in colour. Yet in a shop you see jeans that look soft, a little faded and already lived in. Many of them got that look in a big washing drum filled with rough volcanic stones. The method is called stone wash, and it changed how the world buys jeans in the 1980s. It is still used today, often with newer tools beside it.
This guide explains what a stone wash is, how it is done in a garment factory step by step, and how it differs from enzyme wash and acid wash. It includes a worked recipe with real quantities, the problems you may meet and the safety points. For the full range of finishing methods, see our guide on the denim washing process. To understand the cloth itself, read about how denim fabric is made.
What is stone wash
Stone wash is a garment washing method in which jeans are tumbled in an industrial washing machine together with pumice stones, with water. The stones rub the surface of the cloth and scrape off a little of the blue indigo dye, mainly from the raised yarn on the surface. This gives a faded, worn look and a softer feel.
Denim is made with indigo-dyed warp yarns and white weft yarns. Indigo sits mostly on the outside of the yarn, like a thin coat on a rope. The stones wear this outer layer, so the white core shows through. That is the reason for the light, uneven fade. If you want to know more about the cloth, see our guide on what denim is.
Why stone wash is used
- To soften stiff, raw denim so it feels comfortable from the first wear.
- To give a worn look, with fades and contrast.
- To shrink the garment in a controlled way before it reaches the buyer.
- To remove surface hairs and loose fibre.
- To set the final shade as the brand wants it.
What are pumice stones
Pumice is a light, rough volcanic rock full of tiny bubbles. It floats on water and has a sharp, abrasive surface. For washing, pumice is sorted by size.
| Size | Typical use |
|---|---|
| Small (about 1 to 3 cm) | Gentle fade, thin or light fabrics |
| Medium (about 3 to 5 cm) | Common for jeans |
| Large (above 5 cm) | Strong, patchy abrasion, heavy fabrics |
The stones wear down as they tumble and turn into fine pumice dust and sludge. They are weighed and replaced in time.
The stone wash process step by step
- Desizing. Denim fabric carries starch size from weaving. The jeans are first washed with an amylase enzyme at about 50 to 60 degrees Celsius to remove it. Without this step, the stones cannot work evenly.
- Loading. Jeans and pumice stones are loaded into the washing machine. A typical ratio is 1 kilogram of garments to about 1 to 2 kilograms of stones, though the exact number depends on the look wanted.
- Stone washing. Water, a lubricant and sometimes a small amount of detergent are added. The drum rotates and the stones rub the jeans. Time is usually 20 to 60 minutes at 40 to 60 degrees Celsius. A longer time and a bigger load of stones give a stronger fade.
- Draining and rinsing. The dirty water and dust are drained. The jeans are rinsed.
- Removing stones. Stones and dust are taken out by hand or by a screen. Pockets and seams are checked for stone bits.
- Softening. A silicone or cationic softener is added in a final bath.
- Hydro-extraction and drying. The jeans are spun to remove water, then tumble dried.
- Finishing and inspection. Loose threads are trimmed. The jeans are pressed and checked against the approved sample.
Different brands add steps such as hand scraping, whiskering, potassium permanganate spray or laser. Our guide on the denim washing process covers those.
Stone wash vs enzyme wash vs acid wash
| Point | Stone wash | Enzyme (bio) wash | Acid wash |
|---|---|---|---|
| What does the work | Pumice stones rubbing | Cellulase enzyme with some tumbling | Pumice stones soaked in a bleaching chemical |
| Look | Even to patchy fade, soft | Soft, smooth, less contrast | High contrast, white patches and marbling |
| Fibre damage | Moderate, can weaken seams | Low to moderate | High if done badly |
| Water use | High | Medium | High |
| Waste | Pumice dust and sludge | Less solid waste | Chemical in effluent |
| Common today | Yes, often in combination | Yes, very common | Used for fashion looks |
The name “acid wash” is misleading. It does not use acid in most cases. Dry pumice stones are soaked in a bleaching solution such as potassium permanganate or sodium hypochlorite, then tumbled with dry jeans. The chemical touches only the places where the stones touch the cloth, which makes the marbled pattern. Afterwards the jeans are neutralised, for example with sodium metabisulfite, and rinsed.
What is enzyme wash
An enzyme wash uses cellulase, a natural enzyme that loosens tiny surface fibres of cotton. The loosened fibre and the dye on it are then removed by the tumbling action. It gives a soft, smooth surface. Many mills use a mix of stones and enzymes, which cuts the amount of stone, the fibre damage and the dust.
Acid cellulase works at a pH of about 4.5 to 5.5 and 50 to 55 degrees Celsius. Neutral cellulase works at a pH near 6 to 8 and similar temperatures. Neutral enzymes cause less back-staining, which is the redeposit of dye onto the white parts of the garment.
Worked example: a stone wash batch
A washing unit runs a load of 250 pairs of jeans. Each pair weighs 0.70 kg after desizing.
Step 1: garment weight.
- Total weight = 250 × 0.70 = 175 kg
Step 2: water. Use a liquor ratio of 1:8 for the stone wash step.
- Water = 175 × 8 = 1,400 litres
Step 3: stones. Use a stone to garment ratio of 1.5 to 1.
- Stones = 175 × 1.5 = 262.5 kg, so about 263 kg of pumice
Step 4: enzyme and chemicals. The recipe is neutral cellulase at 1.5 percent of garment weight (owg), and the pH is held with a buffer.
- Enzyme = 175 × 0.015 = 2.625 kg
Step 5: time and temperature. 40 minutes at 55 degrees Celsius.
Step 6: heat for the batch. To heat 1,400 litres of water from 25 to 55 degrees Celsius:
- Heat = 1,400 × 4.18 × 30 = 175,560 kJ, or about 176 MJ
Step 7: weight loss. A strong stone wash may remove 3 to 5 percent of the garment weight as dust and fibre. If a batch loses 4 percent:
- Loss = 175 × 0.04 = 7 kg of fibre and dye in the effluent
Step 8: pumice wear. If pumice wears at about 5 percent per batch, the unit must top up 263 × 0.05 = 13 kg per load. For 6 batches a day, that is about 79 kg of stones a day, in addition to the sludge to dispose of.
These numbers are examples. Recipes differ with the fabric, the machine and the look. Always run a trial on a few pairs and match it to the approved sample before running the bulk.
Machines used for stone washing
Stone washing is done in industrial garment washers. The most common are front-loading drum machines with a perforated inner drum and a solid outer shell. They hold from 50 kg to more than 500 kg of garments and have controls for water level, temperature, drum speed and time. Some have a reverse mode, so the drum turns both ways and the garments do not tangle.
Look for these points when you choose or inspect a machine:
- Inner drum lifters: Ribs that lift the load and drop it onto the stones. Worn ribs give weak and uneven abrasion.
- Drum perforation: Holes must be sized to let dust and fine sludge out but keep the stones in.
- Drain size: A wide drain stops pumice blocking the outlet.
- Door seals: Stones can damage rubber seals over time.
- Load size: A drum filled to the rim cannot tumble. A guide is to fill it to about half its volume with garments and stones together.
- Heating: Steam injection or direct heating should hold a steady temperature, since a 5 degree swing changes the speed of an enzyme.
A wash lab keeps a small sampling machine as well. It is used to build a recipe on a few garments before the bulk lot. The recipe is then scaled up by weight. Because a bigger drum tumbles differently, the first bulk batch is still checked against the approved sample and the time adjusted if needed.
Effects on the garment
- Colour: Lighter, with contrast on seams, edges and raised areas.
- Hand feel: Softer and more flexible.
- Size: Shrinks a little in length and width. The size must be allowed in the pattern.
- Strength: Tensile and tear strength may fall. Hard washes can weaken the fabric, especially at seams, pockets and stress points.
- Weight: Slightly lower.
- Surface: Fuzzy hairs removed. Edges can become frayed if over-washed.
Common problems and fixes
| Problem | Cause | Fix |
|---|---|---|
| Uneven fade between pairs | Stones worn, load not even | Check stone size and weight, keep load constant |
| Back staining (blue on white pocket linings) | Dye redeposits | Use neutral enzyme, anti-back-staining agent, fresh water |
| Holes or torn seams | Too many or too hard stones, too long | Reduce time and stone ratio, test strength |
| Stone bits left in pockets | Poor cleaning | Check pockets, use screen and mesh |
| Yellowing | Too much bleach or poor rinse | Control chemicals and rinse well |
| Different shrinkage | Poor desizing or bad fabric lot | Test shrinkage on every lot. See shrinkage control |
| Rough hand | Poor softening | Adjust softener recipe |
Environmental and health points
Stone washing uses a lot of water and creates pumice sludge, which blocks drains and has to be cleaned out of the effluent plant. Pumice dust can irritate the lungs, and long exposure to fine mineral dust can harm health, so workers should wear masks and the area should have dust control. Chemicals such as potassium permanganate, hypochlorite and strong alkali need gloves, goggles and safe storage. Never mix bleach with acids or with other cleaners.
Many brands now ask for lower impact methods. These include laser fading, ozone treatment, less water machines and enzyme-only washes. See our article on sustainable denim for the wider trend. Treatment of the wash water is also important, as explained in our guide on the water treatment plant process in industry.
Can you stone wash jeans at home
Using a full load of real pumice in a home washing machine is not a good idea. It can scratch the drum, block the drain and break the machine. If you want a lighter, softer look at home:
- Wash new jeans inside out in cool water, then air dry. This softens them slowly.
- Rub a small pumice block lightly by hand on the places where you want wear, such as the thighs and hems. Work gently and test on the inside seam first.
- Avoid pouring bleach on denim, since it can weaken the fibre and give uneven patches.
For sewing denim at home, see our guide with easy tricks to sew denim at home.
Final thoughts
Stone wash turns stiff dark denim into the soft, faded jeans most people want. The idea is simple: stones, water and a spinning drum. The skill is in the details, such as the stone ratio, the time, the temperature and the enzymes. Keep tight control of the recipe, test strength and shrinkage, and look after workers and wastewater. Then the jeans come out looking good and lasting well.
Frequently asked questions
Stone wash is a finishing method where jeans are tumbled with pumice stones in a washing machine to fade the colour and soften the fabric.
In a stone wash, plain pumice stones rub the denim. In an acid wash, the stones are soaked in a bleaching chemical, which gives a high contrast, marbled look.
Usually no. The chemical is typically potassium permanganate or sodium hypochlorite, both oxidising agents, not acids.
Stone wash uses stones to rub the fabric. Enzyme wash uses cellulase to loosen surface fibre. Many mills use both.
It can, especially if the wash is strong or long. Controlled recipes and strength tests keep the fabric within limits.
Usually 20 to 60 minutes in the main stage, plus desizing, rinsing, softening and drying.
It uses a lot of water and makes pumice sludge. Mills reduce the impact with enzymes, lower liquor ratios, laser and ozone options and good effluent treatment.
