The most basic lining is a good quality sateen. A satin weave is more pliable than a plain weave. My go-to lining is a 100% cotton sateen in pale ivory. This is the equivalent of wearing a slip under your dress (fellas--use your imagination!). The lining protects the face fabric and gives body to the treatment. If the face fabric is white or has a white background, it is important
with white sateen with ivory sateen
to choose a white colored lining so that there is no yellowing of the face fabric. Sateens are also available in tan or putty. Colored linings differentiate custom window treatments from ready-mades and also have nice curb appeal on dark colored or brick homes.
Interlining is a lining that is sandwiched between the face fabric and the drapery lining. Interlining is primarily used to add body and give a rich elegant look, particularly when used with silk. The interlining layer can be heavy flannel, English bump, or a 3-layer woven blackout. If you have budget or space constraints and can't use multiple width panels, consider adding a layer of interlining to help plump up single width panels. Another option for the budget conscious client is to use a napped sateen lining with silk. Napped sateen is a sateen lining that has undergone additional processing to brush and raise the fibers on one side. Silk with napped sateen looks much better than silk with only a basic sateen but it is NOT a replacement for interlined silk draperies!
Traditional blackout linings contain several layers of acrylic foam. The layers block light and provide excellent thermal insulation. In recent years, there have been several advances in blackout linings making them more fluid and better draping, but they still have a drawback when used in roman shades. Pin holes are formed when rings are sewn on the shades. One option to overcome this is to use the technique known as French blackout where there are four layers in the window treatment: face fabric - interlining - black sateen - ivory (or white) sateen.
As a custom workroom to the trade, I stock many different linings and special order as needed. I discuss lining choices with my designer clients and quote the best fit for each project/end customer. But I have been known to switch linings (after talking to the designer) during the fabrication process because after seeing and touching the face fabric, I just can't let a window treatment experience a wardrobe malfunction!