In recent years, spinners have complained of the increasing quantities of short fibres which they are finding in cotton bales. By contrast, we have shown in our laboratory that the percentage of short fibres in seed cotton is low and that more than 90 % of these short fibres are located at the micropylar end of the cotton seed. Between the seed cotton on the plant and the bale, the fibres are subjected to several mechanical operations - mechanical harvesting in industrialized countries, cleaning, ginning and possibly more cleaning. It is obvious that those mechanical operations are causing fibre breakage which result in the creation of short fibres. Interest in the nature and strength of the attachment between fibre and seed has been growing recently based on the expectation that varieties with a low degree of attachment would pass through mechanical operations with less fibre damage.

They should require less vigorous ginning which would result in less damage and fewer neps. Under equal ginning conditions, a higher out-turn could also be expected. However, it is clear that the attachment force (Fa) is not the only parameter involved in fibre breakage. Fibre strength and fibre length are certainly also of importance but these parameters can be easily measured by existing equipment.

Some work on fibre to seed attachment forces has already been carried out by Smith and Pearson (1941), Iyengar (1954) and Chapman (1969-72). The instruments proposed were a small tensile tester (Iyengar) working at a constant rate of loading of 20 cN per minute or a modified Scott tester (Chapman). Both instruments are static loading machines which have actions far removed from commercial ginning where tufts of fibres are roughly ripped from the seeds at high speeds.

After much discussion and experimentation, a ballistic tester has been developed in which a bundle of fibres is snatched from the seed in a shearing movement which is similar to that involved in actual ginning.