Polyester thread

Polyester thread is spun (or more often filament-wound) synthetic fiber that has largely replaced rayon as the default embroidery thread since the 1990s. It runs most commonly at 40wt for general logo work, comes in enormous color libraries matched to standard systems like Isacord and Madeira, and holds up to tensile stress on high-speed multi-head machines running 800-1000+ stitches per minute without shredding.

This is the thread we reach for on anything that's going to see a commercial laundry cycle or years of wear — restaurant uniforms, hotel housekeeping shirts, gym towels, hi-vis workwear. A polo embroidered with polyester and run through an industrial wash 200 times still looks close to day one; the same logo in rayon would fade and dull noticeably by then. It's also the safer pick for anything that might see bleach or chlorine, like pool-staff shirts or medical scrubs.

Pros spec polyester by default for uniforms, workwear, and anything with a long service life, saving rayon for retail and gift items where sheen matters more than years of laundering. Cost is roughly comparable between the two at retail, so the decision comes down to expected wear and wash conditions rather than price.

Buyers sometimes think all embroidery thread is interchangeable and are surprised when a logo on a well-worn uniform shirt looks duller than a newer one — that's almost always a rayon-vs-polyester difference, not a manufacturing defect. If a garment is going into heavy rotation, ask for polyester thread specifically rather than assuming the shop defaults to it.