I saw a pretty scarf treatment at a Ladies Night show recently. Someone took a store-purchased scarf and sewed 2 lines down either side about 4 inches in from the 2 edges with elastic thread.  When I stretched out the scarf, the stitching stretched out.  When I let go, the scarf ruffled up on both sides making pretty, soft ruffles.  The elastic thread was on both sides, meaning that it was used on the top thread and bobbin.  Does anyone know how this was done?  I have never seen elastic thread that was thin enough to be used like this. How was the elastic thread used in a bobbin?  Thank you.  Nancy