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Retting: 'loosening' of the bast fibre from the core material in the plant stalk
After harvesting, the hemp straw remains on the land for several weeks. During this period, microorganisms weaken the glue layer between the bast fibre and the woody core in the plant under the influence of water (rain and dew); this process is called 'retting'. During retting, the hemp is turned several times to make sure the retting process is homogeneous and optimal. By weakening the glue layer (pectin layer), the fibre and core material (shives) can eventually be separated during the further processing step (§6§6.1 for technical application and §7§7.1.1 for textiles). The exact duration of retting depends on the weather; decomposition depends on rain, dew, and temperature.
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When the retting process proceeds beyond needs, the stems are over-retted: the hemp fibres become weaker and have a lower value. Over-retted hemp results in relatively large share of short fibres during scutching and hackling (§7§7.1.1, 7.1.3). Conversely, when the straw is under-retted, separating the bast fibre from the core material will require more energy (§6.1), which also results in damages to the fibres.
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