Smocking adds more detail and drama to the top of your curtains. If you want to make a minor change to your existing curtains, it's relatively simple to do, but it looks as if it took a lot of time. Smocking works best for stationary curtains, those that you don't pull back and forth, and with fabrics of medium to heavy weight. Smocking also looks best on fabrics with little to no pattern, since the smocking tends to stand out better against plain fabric.
Turn the curtains right side up and position the smocking tape approximately 1/10-inch away from the top edge of the curtain. Make sure that the hook pocket faces upward.
Tuck the raw edges under, and secure the smocking tape to the curtains with pins.
Sew across the top and of the tape with a sewing machine. Sew across the tape only in one direction to prevent the fabric from puckering.
Tuck under any raw outside edges of the tape, and sew both of the edges of the tape vertically.
Pull on the cord at one end of the tape slowly and evenly. This will gather the fabric together and create the smocking. Push the pleats across the top of the header evenly as you pull on the cords. Make sure that you have an even number of pleats at the top of your curtains.
Pull on the cord at the opposite end of the tape in the same manner as before.
Thread four strands of embroidery thread though an embroidery needle, and knot it at the end.
Place the fabric right side up, and pinch the first two pleats together, approximately 3/8-inch down from the top of the curtain, and stitch the pleats together with the embroidery thread and needle. Loop the thread over the front of the pleat and then through the back of the curtain through the tape several times.
Tie the thread at the back of the curtain and cut it off. Rethread the needle and move on to the next two pleats. Repeat the pinching and sewing process for each set of two pleats, working across the curtains at the same height, 3/8-inch down from the top. For example, you'll sew together pleats one and two, and then sew together pleats three and four. Repeat pinching and sewing the pleats together until you have gone across the entire curtain.
Pinch and sew the pleats down near the bottom of the smocking tape, approximately 3/8-inch from the bottom. Work your way across the curtains for each set of pleats.
Find the middle between your top and bottom pinched pleats. Pinch and sew the pleats together all the way across the curtains for each set of pleats, but working on the opposite gathered pleats. For example, instead of pinching and sewing pleats one and two, you'll pinch and sew together pleats two and three and then pleats four and five; this creates the diamond pattern in the smocking. Continue pinching and sewing all the way across the curtain until you're done.
Slide your curtains on a rod or attach with curtain clips as normal.