Six soaked sheepskins were dehaired using a standardized
dehairing process as developed earlier [16]. The wet weight after
dehairing was noted for each skin and termed the dehaired
weight. One sheepskin was used for each trial. Six different
percentage of sodium hydroxide were used, viz, 0.25, 0.30,
0.35, 0.4, 0.45 and 0.5 with the float 350% (percentages based
on dehaired weight). The duration of the treatment was one
day with 5 min running per hour for 6 h and left overnight
in the bath. Next day, the pelts were fleshed. The pre-fleshed
and fleshed weight of the skins were noted. The percentage increase
in weight after swelling was calculated from the difference
in weights between the dehaired and pre-fleshed weights.
Cross section pH of the pelts was recorded. The optimal opening
up process was based on percentage increase in weight and
performances of final leather. The pelts were bated and pickled
conventionally. Chrome tanning was done using conventional
tanning procedure. The leathers after chrome tanning were
piled for 24 h. The leathers were then sammed and shaved
to uniform thickness (0.7e0.8 mm). Rechroming was not
done. The wet blue leathers were converted into crust upper
leathers using conventional post-tanning recipe. Then an experienced
tanner assessed the leathers.