Acid Washing of Denim Garments - an over view!

ACID WASH

Acid wash is also considered to produce an worn-out effect that is harsher than stone wash. This treatment is mainly being carried out on denim and coarser varieties of garments.

• Acid wash is also known as  Ice wash, Snow Wash and White wash.

• In acid wash a complete discharge or removal of  color possible

• Uses pumice rocks,  bleaching agents and dyestuffs that are sensitive to the bleaching agents.

• Porous rocks that have a medium to high dusting capability are soaked in solutions of bleaching agents such as sodium hypochlorite or  potassium permanganate.  The chemical is absorbed and is transferred by  the cutting action of the rocks and deposited with the dust onto the garment surfaces.

Some more points a garment washer should take care of during acid wash:

-  Rocks must have ability to

• absorb chemistry in less  than 2 hours
• dust easily
• apply dust evenly on smooth surfaces and on high peaks of garment such
• around cuffs, waist band, fly, side seams, etc. and not in recessed spaces
• in those same areas.

-  Load size in pounds of garments should only be 25 -  33% of  rated capacity to allow for free  tumbling of  the garments and stones and for proper drop distance. 

-  Ratio of  the weight of  the stones to the garments should be
                                    0.5 : 1  for a light wash out
                                      3  : 1 for a complete white out

Procedure for Acid Washing:
1) Load  (25 - 33% rated capacity)
2)  Desize for starch with alpha-amalase enzyme or oxidative desize
3)  Rinse
4)  Extract to a certain uniform moisture
                 60 - 70% light frost
                 70 - 90% medium frost
                 90 - 100%  heavy frost (white-out)
5) Add presoaked stones (machine should be dry)  with ratio dependent 

6) Tumble  for 10  - 30 minutes
7)  Remove garments
8) Neutralize
9)  Soften and/or brighten upon desired effect (0.5-3.0 :  1,  stones to garments)
10) Tumble dry 

Some more points about Acid Washing:

• Stones should be allowed to drip or blotted with waste fabric  to remove
  excess solution to prevent spotting.  Stones can be used up to three times
  in some cases before resoaking is necessary.
• Neutralization usually takes place in another machine and the exact proced
  ure is dependent on the discharge agent used.
  Potassium permanganate (KMnO  and  purple in  solution )  converts
  to manganese dioxide (MnO  which is orange-brown in color)
  which must be neutralized with sodium bisulfite or  hydroxylamine
  sulfate ((NH  OH)  H SO  ).