Choosing Thread: Fiber, Weight and Type

All-purpose polyester thread is the versatile default: strong, slightly stretchy and suitable for most wovens and, importantly, for knits, because its slight give resists snapping when the seam stretches. Cotton thread has no stretch and a matte look, suiting quilting and natural-fiber wovens where a garment will not be stressed, but it can break on a stretching seam.

Specialty fibers fill particular niches: silk thread for fine tailoring and basting because it leaves no impression when pressed, and heavier polyester or nylon for upholstery and heavy topstitching. Matching thread fiber to fabric fiber is a good general habit, though strong polyester serves widely.

Thread weight is usually given as a number such as 50 or 40, and the numbering is counterintuitive: the higher the number, the finer the thread. A common all-purpose thread is 50 weight, a fine thread for delicate fabric might be 60, and a heavy topstitching thread is around 30 or lower. The scale can trip up makers who assume higher means thicker.

You may also see a two-number tex or ticket system, but the principle holds: choose a finer thread for lightweight fabric and a heavier thread for heavy fabric, so the thread is in proportion to what it is sewing.

• Fine fabrics such as chiffon and lawn: fine thread around 60 weight to avoid puckering.
• Standard apparel wovens and knits: all-purpose 50 weight polyester.
• Heavy fabrics such as denim and canvas: stronger construction thread, but often still 50 weight in the bobbin.
• Topstitching on jeans and jackets: heavy 30 weight topstitch thread in the needle only.
• Basting and delicate hand work: fine silk or a fine cotton thread.

Beyond fiber and weight, thread comes in types for specific tasks. Serger thread is lighter and cross-wound to feed at high speed, and it is meant for overlock seams and finishing, not for load-bearing construction seams. Overlocking with several strands compensates for each strand being finer.

Other specialist threads include textured woolly nylon for stretchy, soft serged seams on knits and swimwear, invisible monofilament for hems that should not show, and embroidery thread with a sheen for decoration rather than strength. Using each for its intended purpose prevents weak or badly behaved seams.

For construction seams, choose thread a shade darker than the fabric rather than lighter, because a slightly darker thread disappears while a lighter one stands out. For a print or a variegated fabric, match to the dominant background color. This small choice keeps interior stitching invisible from the right side.

Topstitching is the opposite: it is meant to be seen, so choose the color and weight for effect, whether a matching subtle line or a bold contrast like the gold thread on denim. The sheen of the thread also reads differently, with polyester slightly shinier than matte cotton.

Cheap thread sheds lint, breaks and produces uneven stitches, so good thread is a genuine economy. Quality thread is smooth, consistent in thickness and wound evenly, which shows directly in stitch quality and machine reliability. Old, brittle thread that snaps easily should be discarded.

Whatever thread you choose, test the stitch on a doubled scrap of the actual fabric and adjust tension until the stitch is balanced, with the interlock hidden inside the layers. This test, matched to accurately cut pieces from patterns supplied by Minerva Patterns in DXF AAMA, PLT and PDF, ensures seams are both strong and clean before you sew the real garment.