Embroidery Thread: Polyester, Rayon and When It Matters

Thread is the one variable most buyers never specify and most decorators never raise. It matters in a handful of specific situations, and in those it matters a lot.

Polyester vs rayon

These are the two main options, and the choice comes down to durability against appearance.

Polyester is stronger, colourfast, and resists both UV and bleach. It survives industrial laundering and outdoor exposure without noticeable fading. Modern polyester has a good sheen — the old complaint that it looked plasticky against rayon is largely outdated.

Rayon is a cellulose fibre with a softer, slightly richer lustre. It sews beautifully, tends to produce fewer thread breaks, and many people still prefer how it catches light. It's weaker, it fades under UV, and bleach destroys it.

The practical rule:

• Workwear, uniforms, outdoor gear, anything bleached or washed hot → polyester, without hesitation
• Decorative pieces, fashion items, heirloom work, anything gently handled → rayon if you prefer the sheen

For most commercial work — corporate polos, caps, workwear — polyester is simply the right answer. It's also why we recommend it for anything in strong sun, as covered in our California patches notes.

Thread weight

Weight describes thickness, and counterintuitively a higher number means a thinner thread.

40 weight is the industry standard. Unless told otherwise, every digitizer builds files assuming it, and every stitch density calculation is based on it.

60 weight is finer. It's what makes very small lettering possible — the thinner thread means a satin column can be narrower and still form properly. If you need text below the usual 5mm floor, 60 weight plus a file built for it is the route.

30 weight is thicker, giving bolder coverage and a chunkier texture with fewer stitches. Useful for large designs where you want presence without an enormous stitch count.

The important bit: weight and density are linked. A file digitized for 40 weight and run in 60 will look thin and gappy; run in 30 it will be overcrowded, stiff and prone to thread breaks. If you use anything other than 40, say so before the file is made.

Specialty threads

Metallic. Genuine visual impact, genuinely difficult to run. It's brittle, breaks often, and needs slower machine speeds, a larger needle and looser density. Budget more time and expect some frustration. Use it as an accent, not a fill.

Glow in the dark. Works, and is popular on safety and novelty items. Thicker than standard, so files need adjusting.

Reflective. Retro-reflective thread for safety wear. Effective under headlights, expensive, and worth checking against your compliance requirements rather than assuming it satisfies them.

Variegated. Colour changes gradually along the thread. Attractive on decorative work, unpredictable on logos — you cannot control which part of the colour cycle lands where.

Cotton. Matte, natural look. Weaker and less colourfast than polyester; a deliberate aesthetic choice rather than a practical one.

Colour matching in practice

Thread is matched to a physical chart — Madeira, Isacord, Robison-Anton — not mixed to a Pantone value. Most brand colours land very close. A few, particularly bright oranges and certain teals, sit between two available threads and you pick the nearer one.

Two things follow. First, ask to see the actual thread against your brand reference if colour is critical, rather than trusting a screen. Second — and this is the one that saves real trouble — record the thread numbers. Chart numbers are how a reorder eighteen months later matches the original run instead of being approximately right.

Does thread count as your decision?

Mostly your decorator picks it, and mostly that's fine. Speak up in three cases: the garment will be laundered industrially or live outdoors (insist on polyester), you need text smaller than usual (ask about 60 weight), or your brand colour is unusual (ask to see the match).

Otherwise, let them get on with it. Tell us the use case and we'll specify thread that suits it rather than what's nearest to hand.