Structural Division
Mechanical separation of compound flax fibre bundles into thinner technical filaments occurs during hackling and carding stages of bast fibre preparation. Plant stems contain technical fibres held together by pectinaceous middle lamellae, which require progressive longitudinal division to achieve spinning fineness. Processors monitor bundle splitting to ensure that raw stricks transition into uniform slivers without generating excessive short fibre waste.
The operation determines the ultimate linear density achievable during wet spinning.
Mechanical Separation
Pin sets on hackling frames apply high shear forces parallel to the fibre axis, cleaving weak inter-bundle pectin bridges. Modern mills regulate pinned roller speeds and pin density settings to control the degree of division across successive hackling zones. When mechanical action is too gentle, coarse intact bundles pass into the sliver, causing thick places and uneven draft during roving.
Conversely, aggressive mechanical impact fractures primary cell walls, producing broken fragments rather than long split filaments. Mills document this process in internal hackling quality logs, noting the balance between bundle division and fibre breakage.
Fineness Limit
Pectin degradation achieved during retting establishes the ultimate boundary of longitudinal division. Chemical retting residue limits how far mechanical pins can divide bundles without snapping individual ultimate cells. Standard mill inspections evaluate the resulting fibre fineness before sliver drafting, verifying that bundle splitting has achieved targeted decitex values without compromising tensile strength.
