Many knit garments will benefit from a lining. This may be due to a number of factors, including the sheerness of the fabric, the need for a protective underlayer, or the comfort of the wearer. When lining a knit garment, it is wisest to choose a lining that has similar properties to the outer fabric. A knit lining is a beautiful addition to your garment!
Most knit linings are synthetics; if this is the case with your lining, pretreat by machine washing in cold water, then dry in a cool dryer. You may also choose to hand-wash your lining and lay it flat to dry.
Use a ballpoint/jersey needle (size 75/11) for sewing knit linings. All polyester thread is the best choice for sewing these fabrics.
Use a stretch stitch or a small zigzag (2.0 length, 1.5 width) for seams in knit linings. If you have a serger, use a 3 thread balanced stitched, or you could choose to use a rolled hem stitch for seaming lightweight knit linings. Knit linings do not ravel; seam finishes are not necessary. Hems in knit linings are often incorporated into the lining of the outer garment. If you are hemming the outer fabric by hand, do so by pulling your stitching only through the lining fabric. It will make the hem invisible from the outside. If your lining hem is independent of the outer fabric, use a twin needle hem (size 2.5/75 stretch needle) or a coverstitch hem.
You likely will not choose to interface the lining of your garment; interfacing is generally reserved for the outer garment. However, if you encounter a need for interfacing your lining, use the same interfacing as you are using in the outer garment. In most cases, this will be a knit interfacing such as Fusi-Knit or So-Sheer. Be sure to match the stretch of the interfacing to the stretch of the outer fabric.
Use your linings in tops, tanks, tees, tunics, dresses, pants, or shirts. If you like, you can line only the bodice for modesty, leaving sleeves unlined for coolness.
To handle slippery fabrics and linings as one, spray a washable temporary adhesive such as the type used for quilting or machine embroidery on the lining. Lay the outer fabric over the lining and smooth it into place. This will help control the fabrics as you stitch. After garment completion, hand wash to remove the adhesive. For a nearly invisible lining, use a color close to your skin tone.