Of the 10 M m2 of raw hides produced annually in Bangladesh
only a fifth is tanned by 175 odd tanneries, using imported tanning
materials. Vegetable tannins can be extracted from roughly 10,000
tors of mangrove barks available annually at the felling coupes in
the Sundarbans. Amelioration of the properties of these tannins is,
however, a precondition to their use as tanning materials.
Tannins were extracted by various methods from goran {Ceriops
decandr a), kankra (Brugiera gymnorrhiza) and passur {Xylocarpus
molluccensis) barks collected from the Sundarbans. The percentages
of tannins obtained were 24, 21 and 17 respectively. A method was
developed for overall purification and improvement of colour and
quality of tannin. Chemical analysis indicates that the tannin is of
catechol group and quantitative analysis of the extractives shows that
the production of mangrove tannins would be an economically viable
proposition. Tanning experiments with goat skin show that light coloured
and fine-grained uppers and soles can be made with the purified tannins.
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