Traditional Sri Lankan palm vinegar acetification: wooden troughs and mother-of-vinegar?

Crafting authentic Sri Lankan coconut vinegar (Pol Kadi) relies on traditional surface-culture acetification. Fermented sweet toddy (4-6% ABV) is transferred into shallow wooden troughs (vats) fashioned from Halmilla or teak. Unlike submerged aeration tanks in industrial plants, traditional makers rely on natural surface contact with air. Unpasteurized "mother of vinegar" (a gelatinous cellulose biofilm composed of Acetobacter aceti strains) is floated across the liquid surface. Over 60 days at ambient tropical temperatures (28-32°C), bacteria oxidize alcohol into 5% acetic acid without mechanical stirring.