If you prepare your lining and interlining fabric you'll be able to concentrate on the actual drapery making itself, and not worry if you've left anything out. Working in logical steps makes any activity easier to manage, whether it's cooking or making drapes.
You'll have worked out how many widths of fabric you need, and the cut lengths. From this you can work out how much lining is needed. It's easy to work out the lining quantity if the lining width is the same as the fabric. If it isn't, make sure you have enough widths of lining to match the total fabric width.
When the lining is the same width as the fabric, the amount required is the same as that of the fabric. (There's only a few inches involved so it's really not worth bothering with.)
If your fabric was patterned, you could reduce the quantity by using the cut length rather than the adjusted cut length. Sometimes this could be worth it if there was a large difference between these two values. (See the drapery yardage page)
Use plain seams to machine sew the lining panels. Remember to keep the front sides of the lining together. Once the seams are in place, put the lining face down on the table and press the seams flat while keeping them open.
It doesn't hurt to snip the seams at regular intervals to release any tension.
When your drapes will be composed of an uneven number of widths, remember to have a half width on the outsides of your linings, so they match the drape fabric.
Fold the hem of the lining up 2" (3.0cms) and press it. Then fold it up again, pin it in place, and machine it.
The depth of the lining hem (and drape hem) is a matter of preference. Many workrooms use a 2" hem for their linings and a 3" hem for the curtains. Use whichever you prefer.
When joining your interlining use an overlapping seam which is flatter and less bulky than a plain seam. Use an overlap of between a ¼" and ½" (0.7 - 1.3cms).
With half widths, I prefer to match them up as with lining. But others are of the opinion that this isn't necessary. They are probably right, because the interlining will never be seen, unless stong light coming through shows up the seams. So once again, you decide!
The motto 'Be prepared' is as applicable to making drapery as any other activity! Getting your lining and interlining fabric prepared means you can move on to the next stage of making your drapes with confidence.