Stone Washing

In this Process of denim washing 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 (30–120 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.

Stone washing of denim fabric gives ‘used’ or ‘vintage’ look on the garments. This is due to the varying degree of abrasion in the garment. Traditionally, stone washing of denim garments is carried out with pumice stones to achieve a soft hand and desirable look. The pumice stones having an oval and round shape with a rough surface work as an abradant in washing cycle. The variations in shape, composition, hardness and porosity result in different washing effects in the denim fabric. During washing, these stones scrape off dye particles from the surface of the yarn of the denim fabric which shows a faded, worn out and brilliance effect in the denim fabric. From ring dyeing of denim fabric and heavy abrasion during stone washing, the fading is more apparent but less uniform. Stone washing makes the denim garments more supple so that they fit comfortably. To get the desired washed effect, the stone should be of proper hardness, shape and size. For heavy weight denim fabric, large and hard stones are suitable and last longer. Similarly, smaller and softer stones are suitable for lightweight denim fabrics.

Effect of stone ratio

Stone ratio plays a very important role in color fading of denim. Too low stone ratio which can be said below 0.5:1 has no significant color fading effect in the denim garments. 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.

Effect of stone size

The effect of stone size on the color fading effect is very prominent. The smaller the stone size (2-4 cm diameter), the better is the color fading effect of denim. In addition, small stones can provide an even and uniform abrasion effect, but the color contrast produced is very less as compared to the large stones which gives more color contrast. When we use large stones (diameter = 5-7 cm) there is less uniformity of abrasion.

Effect of stone washing time

Stone washing time effects the most on fading process of denim garment. It is also very important in giving the contrast to the fabric. It is seen that the color fading process starts at the very beginning of stone washing process. The fading process continue as the time is increased. Maximum contrast is achieved after 50-55 min of stone washing, but this greatly depends upon the fabric gsm. Studies has shown that after 90min, 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 labor 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.