(I think I've seen ways to do continuous bias tape, but this method is more than sufficient for most purposes.)
First, get out the fabric you want to turn into bias tape (any width or amount is fine). Get out a good pair of scissors, a ruler, and your trusty framing square (you DO have one of those, right?).
Next, mark a 3" wide strip of fabric on the bias (at 45 degrees to the weft and weave of the fabric; just do forty-five degrees from the selvege edge. An easy way to find 45 degrees is to measure the down the length of the fabric from one corner and make a mark there at the width of the fabric [typically 58 or 44 inches]. A line drawn to the opposite corner from that mark is a 45 degree line). I draw a 45 degree line through one corner and then make a few marks at 3" in from that line. Then, I lay my framing square and strike a line. Chalk works well for me.
Cut your strip out:
Trim the ends to squares.
Now, get out your iron (you've got one of those, too, right?) and put a little water in it. This is the part that puts most people off of making bias tape, but it's really not hard.
Now, fold your fabric strip in half like a hot dog bun and press it closed. Pressing is like ironing, but don't just slide the iron down the length; pick it up and press it down, then lift it back up, scoot down some, and press it back down, and repeat. That will prevent the tape from warping.
This will result: (This is called single-fold bias tape, by the way.)
Now. Open your folded strip up partway and fold each edge of the fold in to meet the crease in the middle.
Now, close the fold you've already ironed. You should have this:
Iron the whole thing flat. You should now have a piece of double-fold bias tape! It will be four layers of fabric thick.
To use double-fold bias tape, just wrap the main fold around the edge of whatever you want to seal and stitch it down! The fact that the tape is cut on the bias means that it will curve around even heavily curved edges.
That way, you bind the entire edge such that no unfinished edges are still exposed. Your garment will not have little stringy bits falling off all the time, won't rip from the edges in, and won't unravel when you wash it.
Good luck making and using your very own custom bias tapes!
(Garment shown is my new gambeson (still in progress). It will be posted about at a later date.)
