By: Patricia Bel-Berger and Grant Roberts
Introduction to Neps
What is a cotton nep - what do they look like?
A nep can be defined as a small knot (or cluster) of entangled fibres consisting either entirely of fibres (i.e. a fibre nep) or of foreign matter (e.g. a seed-coat fragment) entangled with fibres. In contrast to the loose arrangement of a worsted nep, a cotton nep generally has a tight formation.
In most cases, fibrous neps are found to contain at least five fibres, with the average number being 16 or more. (van der Sluijs, 1999). The structure of a raw cotton lint nep has been described by British Standards Institute as well-defined and as containing a core structure of relatively dense entangled fibres. This core typically ranges from 0.3 to 3 mm in diameter and may contain a piece of trash or seed; pieces of seed without attached fibres are not neps (Verschraege, 1989). From this core, an array of fibres extends 5 to 10mm, sometimes even up to 25 mm, in length. 1
Due to the apparent differences of formation, there are different classifications for neps. Neps have been grouped in three ways: seed coat with entangled fibres; trash with entangled fibres, and solely entangle fibres without contaminating particles, which primarily consist of immature or dead fibres. In addition, neps are defined in two distinctions as either mechanical or biological.
Biological neps are neps that contain foreign material, whether the material is seed coat fragments, leaf, or stem material (Figure 1) (Hebert, 1988). In unginned cotton, biological neps are typically associated with motes (malformed seed, unfertilized ovules, and dead seed), while in ginned cotton (i.e. cotton lint); they typically contain seed-coat fragments (SCF).
Mechanical neps are those that contain only fibres and have their origin in the manipulation of the fibres during processing (Figure2) 1.
The last type is a shiny nep or white speck nep, found on the surface of dyed fabrics, they appear as light or white spots and are seen only in the finished fabric (Figures 3 and 4) 4.