Window valances are short pieces of ornamental material hung or draped over the top edges of windows. Hemming window valances can sometimes be tricky, but with care, anyone can do it.
Consider Your Options
Is the fabric you have chosen sheer or opaque, natural or synthetic, brocade or organdy? The varying care requirements of fabrics affect which techniques you can safely use.
What type of valance do you like? Choose from gathered, swag, shaped, or box.
For those with minimal sewing skills you can try anti-fray, fusible webbing, or fabric glue.
Anti-fray is a liquid applied to raw edges to prevent them from fraying. This is particularly great if you're using filmy fabric and are creating an uneven or "ragged" hem. Just cut the hem the way you want it and apply the anti-fray right along the edges on the "wrong" side of the fabric. Experiment on a scrap until you get the knack. It is suitable for gathered, swag, and some shaped valances.
Fusible webbing comes in narrow strips for hemming; one brand is Stitch Witchery. Create a hem by turning a narrow length of fabric up to the backside ("wrong sides together"), put a strip of webbing between the layers and press with an iron for a few seconds. The webbing melts and becomes invisible, making it ideal for those filmy fabrics that can withstand heat. Suitable for gathered and swag valances.
Fabric glue works similarly to fusible webbing, without the heat. Turn a narrow strip (1 inch or so) of fabric over, wrong sides together. Use an iron if possible to make a crease. Run a narrow bead of fabric glue between the layers and press together. Make sure no glue oozes out, then put weight on the edge until it dries. It's a little heftier than fusible webbing, and less invisible than anti-fray, so avoid using it on the sheerest fabrics because it will stiffen slightly and interfere with the "hang." Suitable for gathered and swag valances.
You can also try a blind stitch. Turn fabric to the wrong side twice, first about ¼ to ½-inch, then again about 1" to eliminate all raw edges. Straight-pin the edges (perpendicularly) to hold in place and press with an iron if possible. With matching thread, run the needle inside the fold for perhaps ½", then out to grab just a few threads of the "front" of the valance, then back into the fold. This should produce a hem that is nearly invisible on the front of the fabric. Suitable for all heat-tolerant fabrics and gathered and swag valances. It can be done without pressing but is harder to control.
A rolled hem is another option. This is used mostly on sheer fabrics and can be tricky. It's a tiny blindstitched hem like you'll find on a silk scarf. The trick is to keep the raw edges rolled under as you sew, use one thickness of thread, and take small stitches. Suitable for gathered, swag, and some shaped valances.
Using Sewing Machines
A simple, well-sewn single row in a matching color does the trick simply and unobtrusively. An alternative is to make the stitching part of the design, using the many decorative stitches most machines now offer. The key is to sew straight and even. If your machine doesn't have fancy stitches, you can make a simple but striking statement with rows of straight stitches, perhaps in contrasting colors.
You may want to make your valance hang in scallops, points, or other shapes. While you can cut the shapes and use anti-fray, or give them a tiny rolled hem, you can also make them so that they are lined, in either a matching or contrasting fabric, and the hemming is taken care of right as you make the valance.
Pin two shaped pieces wrong side together, and machine stitch all around the shaped edge of the valance leaving at least ¼-inch seam allowance. Trim the corners carefully and turn the valance right-side out, making sure to gently poke the points out so they're sharp. Press and you've got instant hem.
Since the fabric is usually stapled around padded pieces of plywood, these need no hemming. You may need to invisibly stitch the fabric of the adjoining corners together—a little blindstitching will do the trick.