Know What You Wear

Thursday, December 21, 2017

Sandblasting on Denim | Health Problems in Sandblasting

What is Sandblasting?
Sandblasting is a mechanical process in which localised abrasion or colour change on the denim garment is created. The process involves blasting an abrasive material in granular, powdered form at a very high speed and pressure through a nozzle, on certain areas of the garment such as knees and elbows as shown in Figure. The treated surface shows distressed/abraded/used look.
Sandblasting on denim
Figure: Sandblasting on denim
The common blasting materials used are sand and metal granules. During sandblasting process, denim garments are first subjected to stone washing to the desired degree of washing and are then sand blasted. A solution of sodium hypochlorite or potassium permanganate is often sprayed on the desired area of the garment in order to obtain the same look. The garment is then neutralised, rinsed, softened and dried. Sand blasting is a water free process and, therefore, no drying is required.

You may also like: Denim Washing Process: Objectives, Evolution, Advantages and Limitation

Advantages of sandblasting process are that:

  1. It is a purely mechanical process that uses no chemicals.
  2. It is a water-free process; therefore no drying is required.
  3. A variety of distressed or abraded looks is possible.
  4. Any number of designs can be created by special techniques.
The procedure of sandblasting is as follows:
  • The individual garment to be processed is put on a table.
  • An air compressor is started and pressure is maintained at 3–4 kg/cm2.
  • The air compressor then stores air in the machine’s cylinder.
  • Aluminium sand or silicon sand [Al2(SiO4)3] is then put in the chamber of the blasting machine.
  • Sand and compressed air are then sprayed over the garments at specific points at a 10–200 degrees angle by a hand spray pipe.
  • Sand passes into the machine by a regulating system.
  • The machine is composed of a blasting regulator and a hand regulator to control the amount of sand and compressed air, respectively.
  • The angle of sand blowing is important. The higher the blowing angle, the higher the fading effect is and higher the risk is of fabric damage.
  • Fading is done on premarked areas.
  • Sandblasting is a hazardous technique; therefore the area should be isolated from other work areas.
  • Handling the sandblasting gun is risky; therefore operators should use safety equipment such as hand gloves, masks and gowns. Production/hours/guns vary from 25 to 45 garments, depending on the degree of fading and the extent of fading to be attained.
  • The faded garments are cleaned by shaking them manually. After sandblasting, garments are washed. The technique used may be normal washing or bleach or bio-stone washing.
Health problems in sandblasting:
Sandblasting removes the dark indigo from a denim garment giving it a popular pre-worn look. This process involves smoothing, shaping and cleaning a hard surface by forcing abrasive particles across that surface at high speeds using special types of sands. These are sprayed onto the selected parts of the denim garments at high pressure through air compressors to remove colour from those areas to create the desired design.

Sand blasting can be done manually or mechanically. The mechanical process encloses the sand and dust particles in blasting cabinets and is–if used correctly–therefore less hazardous for the operating workers. However, manual sandblasting is preferred by factories as it is cheaper because it does not require investment in advanced and expensive industrial equipment. Sand blasting also costs less than other fading methods (like hand sanding) which are more labour intensive. Whilst sandblasting to achieve a worn look on denim is a relatively new phenomenon in the clothing industry, similar methods have been widely used in mining and building industries for many decades and the link between the use of sand blasting and the risk of silicosis has long been acknowledged.

It was the high health risks associated with manual sand blasting process that prompted regulation of the technique in the Europe in the 1960s. Sand blasting can expose workers to extreme health hazards and can cause death within months or years of starting work as a sandblaster. Sand blasting using natural sand is especially problematic because workers inhale crystalline silica dust particles during production, causing serious damage to the respiratory passages. These particles are so tiny that they are invisible to the naked eye.

The body is unable to expel the silica particles, causing diseases such as silicosis. The particles penetrate the pulmonary alveoli and the connective tissue, gradually impairing lung capacity and the workers’ ability to oxygenate blood. Symptoms include shortness of breath; as the disease develops, this is common even when resting. This puts additional strain on the heart, eventually leading to death. However, the progress of silicosis can be slowed if symptoms are diagnosed at an early stage.


You may also like:

  1. Denim and Jeans Manufacturing Process
  2. Different Types of Denim
  3. Denim Fabric Production Process
  4. Denim Washing Process: Objectives, Evolution, Advantages and Limitation
References:
  1. Denim : Manufacture, Finishing and Applications. Edited by Roshan Paul
  2. Sustainability in Denim. Editors: Subramanian Muthu