Filament length, torsional rigidity, fineness, uniformity and cross sectional shape are critical factors for rope strength. The higher the grade, the longer and stronger the fibres. Impurities are a weak point.
Bangladesh and India use different systems, e.g. BTS (Bangla Tossa Special), BTA, etc. are paper trading grades. With the advice of the National Jute Laboratory, we aggregate grading thus:
Grade 1: uniform golden to reddish of the finest structure, min. filament 1.5m very strong and very good lustre, completely free of defects and blemishes, no breaks, dark bark, waste, specks, cuttings or habijabi tangles.
Grade 2: uniform silver grey to golden of fine structure, min. filament 1.25m, strong and good lustre, completely free of blemishes.
Grade 3: clean, sound, light/medium grey to copperish grey of good texture, fairly strong and good average lustre, min. filament 1m, free of blemishes.
Grade 4: mixed colours, fair to average strength, occasional bark and soft specks, but free from runners, min. filament length 0.75m, slightly cropped and gummy tops permissible, free of black wiry tops and root ends.
Grade 5: average colour and strength, min. filament unspecified, occasional bark and speck, croppy and gummy tops permissible, but free of black root ends and runners.
Quality is strength. Analyse and grade your own rope. Take a length and unwind the strands and yarns.