Stonewash is the traditional jeans treatment. Up to the 70ies jeans were sold only as greige, unwashed goods. The “right” look appeared only after wearing longer time and several home-washes. The demand for that used look increased much. It could be done today with
Pumice stone is of volcanic origin. It is formed in the beginning phase of a volcanic eruption, still rich of gas, the magma is loosened by the gasses and during the eruption lava is solidified and a porous structure is formed. The pores have got sometimes very sharp edges giving the pumice stones its abrasive character.
Depending on the mining field the formation goes back approx. 15-20.000 years. The highest amounts were found in Turkey, Greece, Iceland, Philippines, Indonesia, China, Japan, as well as in Mexico, USA and Equador.
About 75% of the pumice stone is Silicium dioxide and ca. 10 – 15% is made of Aluminium dioxide. The rests are Sodium oxide, Calcium oxide, Iron oxide etc.
The used look is put in place due to the fact that the cotton yarn is dyed with Indigo only in the exterior part of the thread. The pumice stones remove only the exterior layer of the thread and the un-dyed, white interior part of the fiber appears. With the pumice stones a very nice used look is possible. But it came out some disadvantages in using pumice stones:
Rapid waste of drum plates
High amounts of sludge in combination with fiber rests and Indigo pigments
Exhausting unloading of machines, cleaning of pockets, loss of time
It was necessary to make trials without stones => acid enzymes were developed as useful replacement of pumice stones. They work at a pH of 4 -5 and are pretty strong. The disadvantages of the pumice stones could be solved with acid enzymes. They are strong but aggressive and unfortunately other trouble appeared:
Acid enzymes are active in the fiber interior and reduces the fastness to tearing
The goods show a much higher Backstaining of blue Indigo (Redeposition)
That’s why neutral enzymes were developed. They work at a neutral pH, 6 – 7 and they are less strong but less aggressive, the tearing fastness is higher and the Backstaining of blue indigo is lower. But the used effect is not the same as with acid enzymes.
Nowadays it is useful to work with a combination of neutral enzymes and pumice stones.
A standard recipe in bulk for a 100 kg load should look like this:
First step desize and rinse
Waterratio 1:5 - Temperature 40 – 45 °C - Time depends on look, 20 to 60 min
100 kg pumice stones size 2 -4 or 3 -5 cm, 50% new and 50% used
1,0% neutral enzymes
1,0% dispergent agent
Rinse, take out stones, rinse again
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