Stone-Wash Treatment for Denim Garments

LIPARI PUMICE AND THE HISTORY OF JEANS
STONE WASH AND PUMICE
In the last three decades there have been two decisive events in the history of jeans, both of which were not only driven by the influence of fashion,
but also by the need to make denim garments more comfortable and hence widely acceptable, for though denim was renowned for being
extremely comfortable, they were in reality not so. The first event regarded the abandoning of rivets, with the substitution of stitching, a problem
which was solved with the help of great technical efforts (and special sewing machines), the second was STONE WASH.
Pumice plays an important role in STONE WASHING. The introduction of Lipari Pumice in the STONE WASH process has above all improved
productivity, i.e. the number of garments processed in a given time and wash volume, the parameters of which essentially determine the acceptability
of the cost.
STONE WASH is a washing procedure that use stones,
mainly pumice, in order to obtain well defined effects.
Every part of the jeans is effected; pockets, belt loops,
stitching and edges all appear “worn and torn” as if the
jeans might be a few years old.
This is the technical difference between bleaching with
sodium hypochlorite (an old method for obtaining a
homogeneous discolouring effect) and the STONE
WASH technique (a new procedure with a localized
discolouring effect). Fashion trends may be the main
reason for this process, but fortunately the material after
STONE WASHING is also softer, more comfortable and
hence widely accepted.
The resulting effects achieved with STONE WASHING,
i.e. the localized discolouration, helps explain why all
other attempts to directly process materials before garment
manufacture, have not met with success, simple
process such as high velocity rotating brushes, have not
in the past and will not in the future ever have a lasting
success.

THE ROLE OF LIPARI PUMICE IN STONE
WASH
As already anticipated, the success of Lipari
Pumice in STONE WASH is essentially due to
the increase in productivity. By using Lipari
Pumice, one can process simultaneously a
large quantity of garments, with an increase in
productivity in the region of 20% to 30% with
respect to pumice from alternative origins,
which are almost always less dense and more
brittle, but also frequently contain a high content
of impurities that end up damaging a certain
number of garments during the washing
process. Hence Lipari Pumice helps decrease
the total cost due to increased productivity,
with less rejects and less rework.
It is however difficult to calculate the
effective consumption of pumice for jeans
(kg / per garment), since one needs to
account not only for the different garment
size, but one must also take into account
other factors:
- The apparent density, porosity and buoyancy
(or not) of the pumice
- The type of washing machine
- The ratio pumice to material
- Percentage of water used in the machine
washing (the lower the value, the
higher the pumice consumption, and the
faster the process cycle time).
However taking into account the data and
experience of STONE WASH customers,
who find that it is possible to complete 4
to 5 wash cycles with Lipari Pumice,
given the average ratio of pumice to garment
material as 2,5 : 1, and with the
average pair of jeans weighing between
700 gr to 900 gr., it is possible to calculate
an average consumption of 350 gr. of
Lipari Pumice per pair of jeans.