Whipped back stitch
Whipped back stitch makes a heavier line than a back stitch. It gives a similar effect to a stem stitch but a touch finer with the added bonus that it can be stitched in two separate colour threads if required. This technique is useful when a raised line is required on a fabric which is too delicate for a heavy thread to be embroidered directly through the weave.
For more background see the entry for back stitch.
First, work a foundation row of back stitches ensuring each stitch is equal in size and not too small.
Using a second thread, whip over this line from right to left, as shown, without picking up any ground fabric. Use a blunt-ended tapestry needle for the whipping thread to avoid splitting the foundation stitches.
Structure of stitch
This technique is useful when a raised line is required on a fabric which is too delicate for a heavy thread to be embroidered directly through the weave.
Mary Thomas, Jan Eaton, Mary Thomas’s Dictionary of Embroidery Stitches (Revised Edition) (1989) , p.13