Elastic
Braided, knitted, woven, clear and specialty elastics compared, how to measure and cut elastic to length, casing vs stitched-on methods, and joining the ends so the waistband doesn't twist or roll.
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Sewing elastic is a narrow band with stretchy threads (rubber or spandex) running through it, covered or interlaced with polyester, cotton or nylon yarns. It's used wherever a garment needs to stretch on and then hold close: waistbands, cuffs, necklines, swimwear, lingerie and the shoulder seams of knit tops. The type of construction makes a big difference to how it behaves, and choosing the wrong one is behind most twisted, rolling or saggy waistbands.
Types of elastic
| Type | How to recognise it | Behaviour | Best for |
|---|---|---|---|
| Braided | Ridges run lengthwise; narrows when stretched | Lighter grip; loses stretch if stitched through | Casings, sleeves, light waistbands |
| Knitted | Soft, thin; stays the same width when stretched | Can be stitched through; softer | Light to medium fabrics, stitched-on waistbands |
| Woven (non-roll) | Firm, stable, often with horizontal ribs | Strongest grip; resists rolling | Heavy waistbands in casings, trousers and skirts |
| Clear elastic | Transparent polyurethane strip | Very stretchy; light | Stabilising shoulder seams in knits, swimwear, gathering |
| Lingerie and plush-back | One soft side, often a decorative (picot) edge | Soft against the skin | Underwear, bras, sleepwear |
| Swimwear elastic | Rubber or chlorine-resistant | Resists chlorine and salt water | Swimsuits |
| Buttonhole elastic | Slots along its length | Adjustable on a button | Children's and maternity waistbands |
How much to cut
Elastic has to be shorter than the body measurement to grip, but how much shorter depends on the elastic's stretch and the effect you want:
- Waistbands: a common starting point is your waist measurement minus 2-4" (5-10 cm), or about 85-90% of the waist. Firmer elastic needs less reduction, very stretchy elastic more.
- Cuffs and leg openings: wrap the elastic around the wrist, arm or leg at a comfortable tension, without stretching it.
- The best method: wrap the elastic around the body where it will sit, stretched to a snug but comfortable tension, and mark it. Pin it into a loop and pull it on over the hips or hands before cutting, to check it will still go over the widest part.
Add a seam allowance for joining the ends: about 1/2" (1.3 cm) for an overlapped join.
Inserting elastic
In a casing (a channel made by folding over the fabric): the simplest method, and the elastic can be replaced later.
- Make the casing about 1/4" (6 mm) wider than the elastic, so it slides through without twisting.
- Leave a gap of about 2" (5 cm) when stitching the casing.
- Thread the elastic through with a safety pin or bodkin on the leading end, pinning the trailing end to the fabric so it doesn't disappear inside.
- Check it isn't twisted, overlap the ends and join them, then close the gap.
- Distribute the gathers evenly, and stitch through the casing and elastic at each side seam ("stitching in the ditch") to stop the elastic twisting or shifting.
Stitched directly to the fabric: used for knit waistbands, lingerie and swimwear.
- Join the elastic into a loop and divide both the elastic and the garment edge into quarters, marking each point with a pin.
- Match the quarter marks, then stretch the elastic to fit the fabric between pins as you sew, using a zigzag or an overlocker.
- Fold the elastic to the inside and topstitch with a zigzag, twin needle or coverstitch.
Stitching through braided elastic weakens it and makes it narrow and lose stretch, so use knitted or woven elastic for this method.
Joining the ends
Overlap the ends by about 1/2" (1.3 cm) and stitch a square, or a box with an X, with a wide zigzag. This is flatter than a seam. For a thinner join, butt the ends together over a small patch of fabric and zigzag across both edges.
Care and lifespan
Elastic degrades with heat, chlorine, body oils and age. High dryer heat is its biggest enemy, so dry elastic garments on low or line-dry them. Elastic that's been stored for years can lose its stretch in the packet: stretch a little before using old stock, and if it doesn't spring back fully, replace it.