Machine-embroidery thread is commonly sold in polyester and in rayon, and from a few feet away a logo sewn in either looks much the same. The difference shows up later: in the laundry, under a bleach cycle, under an iron, and in the way the stitches catch the light.
This guide compares the two fibers property by property, then looks at what the choice means for color matching — because a polyester thread and a rayon thread with the same name are often not the same color.
The Short Answer
Choose polyester for anything that is washed hard: uniforms, workwear, chef coats, kids' wear, towels and sports kit. It holds up to hot, frequent and industrial laundering, and it is the usual choice where garments are bleached.
Choose rayon for decorative and fashion pieces, monograms and gifts, where its softer, deeper luster is the point and the item will be washed gently and less often.
When in doubt, the garment decides, not the color. A logo on a work shirt should be stitched in polyester even when a rayon thread is the closer color match, because the closer color may not stay close after a season of hot washes and bleach.
What Each Fiber Is
Polyester embroidery thread is a synthetic filament: a manufactured polymer spun into continuous fibers and twisted into thread. It generally keeps its color through hot washes and bleach better than rayon does.
Rayon (viscose) is regenerated cellulose: plant cellulose dissolved and re-formed into continuous filaments. That gives it a soft hand and a rich luster, but chlorine bleach weakens and fades it.
Both are filament threads, which is why both have the sheen that makes machine embroidery look like embroidery, and why both change shade with the direction of the light.
Side-by-Side Comparison
| Polyester | Rayon | |
|---|---|---|
| Fiber | Polyester filament, a synthetic | Rayon (viscose), regenerated cellulose |
| Laundering | Holds up to hot, frequent and industrial washing | Better on garments washed gently and less often |
| Chlorine bleach | More resistant; the usual choice where garments are bleached | Weakened and faded by chlorine bleach |
| Sheen | Bright, slightly harder shine | Softer, deeper luster |
| Heat | Thermoplastic: can glaze or melt if pressed too hot | Cellulosic: scorches rather than melts |
| Typical work | Uniforms, workwear, kids' wear, towels, sports kit | Decorative and fashion pieces, monograms, gifts |
| Robison-Anton colors in our data | 447 codes, 416 distinct colors | 419 codes, 308 distinct colors |
| Cost | Varies by brand and supplier; compare current price lists | Varies by brand and supplier; compare current price lists |
The property rows describe the fibers in general, not any one manufacturer's product. For a specific line's colorfastness, bleach and pressing guidance, check the thread maker's own documentation.
Washing, Bleach and Durability
For most commercial jobs, this is the deciding property. Uniforms, workwear, chef coats and team kit go through hot, frequent and often industrial laundering, sometimes with chlorine bleach. Polyester thread is the fiber built for that: it holds its strength and color where rayon would weaken and fade.
Rayon is not fragile in normal use. A monogrammed gift towel, a decorative cushion or a fashion jacket washed on a gentle cycle is a reasonable home for rayon, and its luster is a real advantage there. The mistake is putting it on a garment whose care routine it was never chosen for — the embroidery can fade while the garment around it does not.
Do not switch a bleached garment to rayon to get a closer color. A rayon thread that matches the brand color on day one is unlikely to match it after the garment has been through chlorine bleach. Sew the nearest polyester option out instead, and get it approved.
Sheen and How Each One Stitches Out
Both fibers reflect light along their length, so stitches running toward the light read lighter than stitches running across it. Rayon's deeper luster makes that effect stronger: the same rayon thread can show as two clearly different shades in one logo, depending on stitch direction. Polyester has a bright, slightly harder shine with a little less of that swing.
Stitch type matters too. Long satin stitches show the most sheen and read brightest; dense fill (tatami) stitches break the light into short runs and read deeper and flatter. A design that relies on luster — a satin monogram, a decorative border — is where rayon earns its place.
Heat and Pressing
Polyester is a thermoplastic: too much heat softens it, and an iron or heat press that is too hot can glaze the stitches to a flat shine or melt them. Rayon is cellulosic, so it does not melt; at too high a temperature it scorches instead.
Either way, the safe rule is the same. Follow the thread maker's pressing guidance, press from the back of the embroidery or through a pressing cloth where you can, and test on a sewn scrap before pressing a finished garment. If a job combines embroidery with a heat-applied decoration on the same garment, the embroidery has to survive that press as well.
Color Range and How Close Each Gets to Pantone
Fiber is not only a durability decision — it changes which colors you can reach. Robison-Anton makes both lines and numbers them separately, so they make a direct comparison:
- Polyester: 447 codes, 416 distinct color values in our data.
- Rayon: 419 codes, but only 308 distinct color values, because far more rayon codes share one color value with another code.
Fewer colors does not mean worse matches. Across the whole Pantone coated deck, the nearest Robison-Anton rayon thread is a median ΔE*00 4.0 away, against ΔE 4.8 for polyester; about 67% of Pantone colors have a rayon thread under ΔE 5, and 53% a polyester one. The two lines simply cover different parts of the color space, and which one lands closer changes from color to color.
Single-fiber lines are a separate question. Isacord, for example, is a polyester line: its nearest thread lands a median ΔE 4.1 from a coated Pantone, and the Isacord polyester thread converter matches against its 387 distinct colors. Comparing brands of the same fiber is a stock decision; comparing fibers is a garment decision.
Same Name, Different Color
The trap in a two-line brand is the names. In our Robison-Anton data, 248 thread names appear in both lines, and 245 of those pairs even end in the same two digits — Foxy Red is 5563 in polyester and 2263 in rayon. It looks like a system you can translate.
It is not. The two threads in a same-named pair are a median ΔE 11.0 apart in color — far beyond anything that reads as a match — and only 24 of the 248 pairs are within ΔE 5 of each other. Never swap one line's code for the other line's same-named thread. Convert from the Pantone in each line separately.
Why Our Robison-Anton Converter Offers Both Lines
Because the fiber is chosen first and the color second, a converter that only matched one line would answer only half the question. The Pantone to Robison-Anton converter has a line selector: Polyester, Rayon, or Both side by side.
- Set it to the line you will actually sew. For a uniform order that is polyester, even where the rayon result is closer.
- Use Both when the garment could go either way — a decorative item, a fashion piece — and you want to see whether one fiber reaches the brand color and the other does not.
- To jump straight to the rayon results, open the converter on the rayon line.
Whichever line you pick, the converter's answer is the first cone to test, not the approved color. The rest of the process — thread card, daylight, sew-out, work order — is covered in matching a Pantone to thread, start to finish.
Frequently Asked Questions
Related Tools
Polyester and rayon thread matches, one line or both side by side.
Closest Isacord polyester threads for any Pantone color.
From the brand guide to an approved sew-out.
Find the closest Pantone for an existing Isacord thread.
Isacord and Robison-Anton thread colors are adapted from the thread palettes of Ink/Stitch, the open-source machine-embroidery extension for Inkscape, which publishes them under the GNU GPL-3.0 license (retrieved 2026-10-13).
PANTONE® is a registered trademark of Pantone LLC. Isacord and Robison-Anton are trademarks of their respective owners. PantoneConverter.com is not affiliated with, endorsed by or sponsored by Pantone LLC, Amann or Robison-Anton. Thread color values shown here are sRGB approximations for on-screen reference and are not color-managed reproductions of the physical thread.