Physical properties of wool of good and poor quality
Home Physical properties of wool of good and poor quality Last update: April 2, 2012 02:00:28 PM
THE PHYSICAL PROPERTIES OF WOOL OF GOOD AND POOR QUALITY J. J. VENTER, Agricultural Research Institute of the Karoo Region, Middelburg, Cape Province 5900 ABSTRACT
Keywords: wool, Merino, physical properties
The physical properties of wool of Merino sheep purposely selected and bred for wool of good and poor quality were compared. For nine successive years (1969 to 1977) midrib wool samples were taken from the two-tooth ewe and ram progeny. The quality of the wool was subjectively assessed and points awarded according to grade; a wool of good quality 4 to 5 points and wool of poor quality 1 to 2 points. The wool samples were analysed for the following properties: fibre diameter, crimp frequency, fibre length, crimp ratio, compressibility, feltability and degree of weathering.
The wool of good quality was significantly (P<0,01) finer, by one to two micro metres, having fewer crimps per 25,4 mm, and was longer than wool of poor quality. Wool of good quality was consequently much more under-crimped and had a significantly (P<0,01) lower resistance to compression and a higher feltability. It was also significantly (P<0,01) more weathered in the tip portion.
A gradual decline in resistance to compression and an increase in felting propensity were noted over the nine years of purposeful selection for good quality wool. Sex differences at the age of two-tooth (18 months) were inconsistent.
Over-emphasizing softness of handle as a prerequisite for good quality may not only cause the wool to become finer but will also cause it to become more under-crimped, flabby and lacking in substance and, consequently, more liable to deeper weathering.
DIE FISIESE EIENSKAPPE VAN WOL VAN GOEIE EN SWAK KWALITEIT
Sleutelwoorde.. wol.. Merino.. fisiese eienskappe
Die fisiese eienskappe van wol van Merinoskape wat doelbewus vir goeie of swak kwaliteit geselekteer en geteel is, is vergelyk. Wolmonsters is vanaf die middelrib vir nege agtereenvolgende jure (1969 tot 1977) van die tweetand-ooie en -ramme geneem. Op grond van subjektiewe beoordeling is 4 tot 5 punte vir 'n wol van goeie kwaliteit en 1 tot 2 punte vir swak kwaliteit toegeken. Die wolmonsters is ontleed ten opsigte van veseldikte, kartelfrekwens, vesellengte, gekarteldheid (d/d'-verhouding), kartelverhouding, weerstand teen same persing, verviltingsvermoë en graad van verwering.
Wol van goeie kwaliteit was oor die algemeen (van een tot twee mikrometer) betekenisvol (P<0,01) fyner, met minder kartels per 25,4 mm en ook langer as wol van swak kwaliteit. Die wol van goeie kwaliteit was gevolglik in 'n groter mate ondergekarteld. Verder het wol van goeie kwaliteit 'n hoogs betekenisvol laer weerstand teen samepersing besit, met onder woorde papper, en het ook 'n hoër verviltingsvermoë gehad. Die wol van goeie kwaliteit was gevolglik ook hoogs betekenisvol meer en dieper verweerd in die tipgedeelte.
Die doelbewuste seleksievoorkeur vir wol van goeie kwaliteit in teenstelling met swak kwaliteit is moontlik die oorsaak dat die wol vanaf 1969 tot 1977 gaandeweg papper geword her met 'n lae weerstand teen same persing en 'n hoe verviltingsvermoë. Geslagsverskille op die ouderdom van 18 maande (tweetand) was in die algemeen wisselend.
Gehalteverskille in wol kan hoofsaaklik gewyt word aan verskille in die aard van karteling in verhouding tot die veseldikte. Die seleksie en teling van Duerden-getroue wol word aanbeveel ten einde die gewenste eienskappe te behou en terselfdertyd weg te doen met ongewenste eienskappe. Published
Agronimalia 12 (3)