Think of thread-basting as a temporary replacement for pins. You need to hold two pieces of fabric together just long enough to applique them together. If it is a small applique piece then a pin or two will do the trick, but if it is a large applique piece (like a Hawaiian or 2 Fabric Applique Quilt) then thread-basting is in order.
Here are our suggestions for basting:
Use a long, single thread (about the length of your extended arm) and a long needle (a straw or milliner's needle). Knot the thread.
Make long running stitches that are about 1" long and 1" apart. Be flexible, it depends on the size and shape of the piece.
Place basting stitches about 1/2" to 3/4" in from the cut edge of the applique piece. This will provide enough room for you to comfortably sweep your needle and turn under 3/16".
No need to put a knot at the end of a thread or line of basting, just 2 to 3 small tacking stitches in place will hold until the basting is removed. Pull the needle off the thread or cut the thread, leaving about a 1" tail.
Basting is not a precision process. Do enough of it to hold your applique piece securely in place, but that's all.
TIP 1: Use an ugly color basting thread. When you pull out the basting, your applique will look even better with that ugly thread gone; increasing your feeling of accomplishment!
TIP 2: Basting is the perfect opportunity to use up thread you don't like, or won't use for anything else. Use old thread, ends of spools, or the thread you no longer like to use for applique. (Beware of thread on old wooden spools. It has absorbed acids from the wood that may weaken the thread and make it less color-fast.)
Why don't we glue-baste? Several reasons:
The applique has not yet been cut when basting a 2 Fabric Applique Quilt, so the edges are not available for glue-basting.**
After carefully placing a Hawaiian applique, we don't want to have to lift it (even the edges) in order to get the glue in.
If we glue so close to the edge of the applique that we don't have room to turn under the edge, we have to tug the fabrics apart and that can distort the fabrics (stretch them out of shape).
Glue is a product that could discolor, or have other negative affects, on some fabrics.