BulkBulk can be defined as wool's filling power or "bounce" and is the volume occupied by wool fibres at a prescribed load. It can be applied to loose wools, sliver, or yarn and is expressed as cm3/g (that is, cubic centimetres per gram) measured in a bulkometer. Loose wools can range from 20 to 35 cm3/g with the values for sliver and yarn being progressively lower. The more the fibres are twisted together the lower the bulk.
The higher bulk wools produce springier and more resilient yarns, making this is a highly desirable property for carpets and knitwear. The extremely high bulk breeds are Southdown, Suffolk and Cheviot and the very low bulk wools are Lincoln and Leicester.
High bulk wools have a helical fibre crimp (like a corkscrew) where each fibre tends to lie independently and the staples look spongy and indistinct. Lower bulk wools have staple crimp where the crimps lie together to form the "character" of the staple. They also usually have high lustre whereas high bulk wools have little or no lustre. Incidentally, high bulk wools do not felt (great for garments, not so good for felters). Low bulk wools felt readily so choose these for felting.
© Pat Old 2002