I received a handful of questions about using elastic thread in the pleater. Yes, you can do it. Martha Pullen even mentions it in her Pleater DVD. I have found there are a couple of tips that make it easier.
1. Cut your pieces of elastic thread about 2 inches longer than needed so you can tie off the rows.
2. Make sure you thread the needles with a needle threader...then only pull about 1 inch of the thread end through.
3. When you have started pleating the fabric and are pulling it off the needles, grab on to all the elastic thread tails hanging down and gently pull them so that the elastic stretches a little. That will decrease the diameter of the elastic and enable the fabric to move onto the elastic a little easier.
4. Determine if size is correct and adjust pleats. Remove threads from each edge for seam allowance needed. Tie off the ends just like when blocking a pleated piece. I tie them off in pairs of two or three if there is an odd one left over.
1. If pleating a piece of fabric allow approx. 4 inches of fabric for 1 inch of pleated fabric. (4 to 1 ratio)
2. If shirring (with sewing machine) a piece of fabric allow approx. 2 inches of fabric for 1 inch of pleated fabric. (2 to 1 ratio)
For ideas of where to pleat with elastic thread:
1. Across the back of a sundress or top.
2. Across the back and front of a sundress or top. You can also still smock when using elastic thread. Just make sure to leave the elastic thread in and tie off.
3. Smocked sleeves. When smocking is finished leave elastic in and tie it off. The elastic also helps keep the sleeve from becoming stretched out and saggy over time.
*As a side note - I personally would not use elastic thread in an heirloom garment, however I do use it in other clothes.