Elastic core yarns based on linen, or hemp, or other materials, and elasticized fabrics therefrom

A method for making an elastic core yarn comprising the steps of:

• providing a core comprising:
• an elastic fibre;
• and
• a continuous yarn arranged along said elastic fibre;
• providing a covering yarn made of a natural fibre, said covering yarn having a linear mass density Nm, said covering yarn twisted with an initial twist direction selected between “Z” and “S” and with an initial number of twists per meter;
• conveying said core towards a collecting bobbin, causing said core to pass through a wrapping space;
• conveying said covering yarn in said wrapping space;
• said steps of conveying said core and said covering yarn taking place at respective conveying speeds,
• helically wrapping said core with said covering yarn in said wrapping space, obtaining said elastic core yarn consisting of said core wrapped by a helix of said covering yarn;
• and
• collecting said elastic core yarn on said collecting bobbin,
• wherein said step of helically wrapping provides:
• causing said number of twists per meter of said covering yarn to decrease from said initial number of twists per meter to an untwisted condition and afterwards to increase in a direction opposite to the initial twist direction, such that said covering yarn becomes twisted with a final twist direction “S” or “Z” opposite to said initial twist direction “Z” or “S”;
• and
• selecting said conveying speeds in order to cause a coil number T of coils, of said helix of said covering yarn wound about one length unit of said elastic core yarn, to be larger than a predetermined minimum value T0 which depends upon said linear mass density Nm, and
• wherein said wrapping space is a space enclosed in a container.