Madeira ‘Smocking’ thread is a special yarn which reacts to heat. Stitch the fabric using Madeira ‘Smocking’ in the bobbin. Run a warm household iron over the stitched fabric slowly and the thread will react to the heat, creating controlled gathering whilst the fabric is unaffected. The rippled or crinkled effects are beautiful and limitless. No special needles are needed, and shrink embroidery can be created on any type of home sewing or embroidery machine.Smocking works well on all home sewing and embroidery machines.