Tulle is a very fine lightweight netting which originated in the south of France. Made from silk, cotton, nylon or rayon, tulle is used in veils, dresses and ballet tutus. Look at your tulle closely. Does it form a tiny pattern of hexagons? If so, it is actually bobbinet, a weave invented in 19th century England that is slightly more durable than a traditional French tulle weave. Because the fabric is delicate, it has a floaty, airy look and is often added to formal wear and wedding dresses to give accent. Unfortunately, it is very vulnerable to tears and damage.
Set up a work area, with a table if possible, next to a window or under a powerful light. Lay your tulle out carefully on top of a dark table or a patch of fabric in a contrasting colour; it is important that you have a good view of the fabric.
Thread the needle with the monofilament.
Make a first stitch, connecting the two sides of the tear, and lay the tail of the monofilament in the place you will be stitching.
Whip stitch the slash in the fabric, sewing over the tail of your thread. Catch one side of the tear, then the other side, then the first side again, and continue to stitch to the end of the tear. Do not go any deeper into the tulle than the closest weave, or you will create gathering, which can be even more visible than a rip.
When you have reached the end of the tear, whip stitch back through half an inch of the repair.
This method will work only if you have a clean tear, with the fabric on either side intact. If there is fraying, extensive damage, a burn or a hole, the only way to repair your tulle is by patching. However, this is not an ideal method, because it will be visible; replacing the tulle is often a better course of action. Repair shops and dry cleaners can mend tulle but will charge high prices as it is fiddly work. If your garment is made from silk tulle, you can use silk thread in a matching colour.
Whip stitch is not a strong stitch, so the area of the rip will be vulnerable. You can use feather stitch instead, but this is more likely to be visible. Do not use glue on tulle. Do not use a hot iron on tulle.