A fabric window cornice needs to have the fabric supported in some way. The three most common ones are:
Here we'll look at using buckram for a stiffening. You can easily adapt the details here when using an interfacing.
I always specified the sewing method as shown here when making cornices for clients, rather than using adhesives. Adhesives react differently to various fabrics, climate, age, etc. Over time they may discolor or even rot fabrics. But if you want to save time then by all means use adhesives instead.
Buckram and interlining
Design the shape you want, and cut it out from card or paper. Mark this shape on the buckram and cut it out.
Take some interlining and cut this to the same shape, then machine it onto the buckram.
Fabric and lining
Cut the fabric and lining, and seam the widths together. Allow about 2" (5cms) for turnings onto the back of the cornice. Remember to have one complete width in the center, unless the pattern dictates otherwise.
Seam the fabric and lining together to form the top of the cornice. An easy way to attach the cornice to the board is to use Velcro. To do this machine a length of Velcro onto the right side of the lining. Set it about ½" (1.3cms) down from the top.
Set the right sides of the fabric and lining together, and machine along the top just above the Velcro.
Put it all together
Now put the buckram between the fabric and lining, making sure the interlining is against the fabric. Pin in place along the top.
With the cornice face down on the work table, trim the fabric to the shape. Make sure you leave a turning allowance.
Here's a hint for the next stage. Always work outwards from the center.
This applies to whatever sort of cornice you're making. Turn the fabric over the buckram until the fabric on the front is flat, then pin it in place. You need to make the fabric taut, but not too much so it warps the buckram. This is where it helps to use a fairly stiff buckram, because it won't warp when slight pressure is applied.
If you have a shape to the base of your fabric window cornice, you'll need to snip the turnings so the fabric can follow the curves. See the diagram on the right.
Now fold the turnings on the sides. Then place the lining in position on the back of the cornice. Cut the lining leaving turning allowances. You'll need to snip the lining turnings in the same way you did the fabric.
Sew the lining to the fabric
Fold the lining under. It should be about ¼" (0.6cms) from the edge. Slip stitch the lining to the fabric down the sides and along the base. A curved needle is often used for this, because it makes it easier to get the needle back through.
Add any trims
At this stage you can sew on any trims such as fringes, braids or trims. Again, a curved needle is best for this. This is one place where adhesives ok to use. The latex based ones are best, as they don't seem to react very much with fabrics.
Fitting your cornice
To attach your cornice, fix the matching Velcro to the front of the mounting board, then attach the top of the cornice to the board. You can crease the buckram where it bends round to form the returns to the wall.
Stand back and admire your work!
Making a fabric window cornice takes a little time and patience, but it's easy to do.