The selvedge, or selvage, is the 'self-finished edge' which runs the length of the fabric. parallel with the warp threads. On woven fabrics the selvedge is usually frayed with two rows of holes.
Because selvedges look different and behave slightly differently to the main body of the fabric, they are not normally incorporated in garments. However, Chanel jackets famously make use of the selvedge as a decorative trim.
Working with selvedges
Try not to use the selvedge with a narrow seam allowance. The selvedge is stiff and behaves differently to the rest of the fabric. If you use it in the seam allowance, usually for the two back pieces of a garment with a centre back zip, remember to clip it, like you do for anything with a curve. This will release the stiffness.
Before laying out your pattern pieces, pinning and cutting, clip the selvedges every couple of inches. This will relase the stiffness at the edges and let the whole weave relax.
Underlining is when a stabilising fabric is used with the fashion fabric, working with both layers as one piece. In the photo you can see that the fashion fabric (pink) and the underlining have been used as one - the bodice darts have been sewn through both fabrics.
Underlining is used for a number of purposes: to strengthen flimsy fabrics (such as georgette) or convert lightweight fabrics for use in more structured garments (such as a jacket); to eliminate undesired stretch from a fabric; to add warmth to a garment; to make an opaque backing for a sheer or see-through fabric (such as lace); to hide seam allowances showing through sheer fabrics; to reduce creasing. Underlining solves so many problems!
The fabric of choice for underlining is silk organza. Silk organza is stiff but light weight making it ideal for the job. Cotton batiste is also popular. However, you can use just about any fabric to underline a garment: experiment with different combinations to find which works best.
The differences between ordinary lining and underlining are numerous. Underlining is worked as one with the fashion fabric and thus it changes the handle of the fabric completely. Lining is usually only joined to the fashion fabric at the armhole or wrist and the neckline, or waistline if you are making a skirt. Underlining is joined to the fashion fabric at every seam. Underlining does not conceal seams on the inside, whereas lining does.
When working with underling, you must allow for what is called 'the turn of the cloth'. Your fashion fabric piece will be slightly bigger than the underlining fabric because it must turn over it. When you press the seam allowances under, the fashion fabric will fall slightly short of the underlining, as above.
"A walking foot has built-in feed dogs that grip and advance the upper layer of fabric that's traveling through the sewing machine in unison with the machine's feed dogs, which grip the underside of the fabric. The action of this special sewing machine foot helps keep the layers from shifting apart as they move through the sewing machine" (about.com).
A walking foot is essential for quilting. It is also really useful for sewing slippery fabrics, piled fabrics (like velvet), bias garments or sewing through a number of layers. If you've ever started sewing a seam with your edges aligned and got to the end and found one piece is significantly overshooting, you need a walking foot!
Try this: grab a piece of ordinary cotton.
- Pull along the length of the fabric. You'll notice that the warp threads have very little give.
- Now pull crossways. The weft threads should feel slightly more stretchy.
- Now, pull diagonally across, in either direction (top left to bottom right or top right to bottom left). You'll notice that the fabric is considerably more stretchy this way. This is called the bias.
Garments cut on the bias tend to drape very nicely and tend to hug the wearer flatteringly. Garments cut on the bias should always be left to hang for at least 24 hours before hemming in order to let it settle. If you don't let it fall, you'll notice bits of your hem seem wonky; they appear to sag even though you had sewn the thing straight!