Fleece fabric is a knitted fabric whose back, or both sides, has been raised into a soft, deep pile. Polar fleece is the polyester version: knitted, napped and sheared, in Polartec’s description of its own fabrics (Polartec 200 Series listing). Raising gives a cloth more heat-holding capacity (US 5,473,801).
- Knitted. A jersey face, with extra yarn held on the back as floats or loops, which are then raised.
- Raised and sheared. Wire-covered rollers pull fibre out of the back yarn; a shearing cylinder levels the pile.
- Fibres. All cotton, cotton and polyester, or all synthetic. Polar fleece is polyester, much of it now recycled.
- Weights. Polartec’s 100, 200 and 300 are weight classes, not g/m² figures. Its own listings give 193 g/m² for a 100 and 251–258 g/m² for a 200.
What fleece fabric is
Cotton Incorporated’s knitting course gives the clearest account (Cotton Works, “Single and double knits”, archived 19 September 2026). In a typical fleece, the yarns that will be napped are knitted on the technical back as floats, and their lower twist lets them raise more easily. A two-end fleece has a face yarn and the back yarn. Leave the back un-napped and the same fabric is sold as French terry. Strictly, French terry is an un-napped fleece: floats make its loops, not a terry sinker. A three-end fleece adds a third yarn, a tie-in yarn between the face yarn and the pile yarn, and is the most stable and fullest fleece. Fleece comes in all cotton, cotton and polyester blends, or all synthetic fibres. The site’s page on knit structures sets these beside the other weft-knit structures, and knitted fabrics and their types lists the fabrics.
Polar fleece is usually made another way. Malden Mills, the company behind Polartec, described it in its patents as a terry knit made on a circular machine by reverse plaiting. A finer stitch yarn forms the technical face, and a bulkier loop yarn lies over it and forms loops on the technical back. Then the fibres are raised on both sides to make a velour on each face (US 6,779,368, Malden Mills). That is why Polartec lists a 100 Series fabric as a “solid double velour” (Polartec 6180 listing).
The word has other meanings. Wool growers call the shorn coat of a sheep or alpaca a fleece. That raw fibre is a different subject, covered on the alpaca fibre page. Fleece can also be woven: a patent with 2005 priority describes polyester fleece pile-woven on a double-side pile loom, with the loops cut and raised (US 7,213,313). Polar fleece, which Polartec calls “a knitted material” (Fleece Series), and the fleeces in Cotton Incorporated’s course are knitted.
How polar fleece is made
1. Knitting
The three-thread fleece in the worked example below was knitted on a circular fleece knitting machine (Hossain et al., 2021). In Cotton Incorporated’s terms its three yarns are a face or ground yarn, a tie-in yarn and a pile yarn, and the loops on the technical back are napped (Cotton Works). For polar fleece’s terry route, Malden Mills gives the yarns. The loop yarn is at least 50% bulkier than the stitch yarn, so the fabric holds together after napping: 150 to 600 denier against 30 to 150. The sinker loops are at least 2.0 mm, because napping pulls them shorter (US 6,131,419, filed 1998). The later double-face patent gives 70–300 denier loop yarn, 50–150 denier stitch yarn and about 28 cut. It gives a fibre fineness of about 0.3 to 1.5 denier (US 6,779,368).
2. Raising (napping, brushing)
A raising machine is a large cylinder carrying smaller rollers clothed in card wire. On the pile rollers the wires point the way the fabric travels; on the counter-pile rollers they point the other way. The patent says finding the balance between pile and counter-pile raising energy is “extremely difficult”. Too much counter-pile action can over-nap and even tear the cloth (US 4,803,761, Leo Sistig). The wire works by a difference in speed between rollers and fabric. It gives the cloth more heat-holding capacity and “a wooly, fleecy handle” (US 5,473,801, Textilmaschinenbau Aue).
3. Shearing
A shearing machine has a cylinder with helical blades that turns against a fixed ledger blade. A cloth rest pushes the pile up into the gap between them, so the pile is cut to a height set by the spacing of the parts. Those parts must be straight and parallel, or the shearing is uneven (US 5,379,498, Guilford Mills). When a fabric is napped on one face and its loops cut on the other, the shearing has to come after the napping (US 6,131,419).
4. Heat setting and finishing
The double-face fabric is heat set to stabilise its width (US 6,779,368). Mills also finish to resist pilling: see pilling below.
Worked example: where the weight of a fleece goes
Hossain and co-authors knitted a three-thread fleece on a 34-inch, 20-gauge machine (Heliyon 7, e06921, 2021). The face yarn was 30 Ne, the binding yarn 100-denier polyester filament and the fleecy yarn 10 Ne cotton. Stitch lengths were 4.6, 3.1 and 1.8 mm, and the grey fabric weighed 264–274 g/m². Put those yarns and lengths into the site’s fleece and terry loop length calculator, converted to 19.7, 11.1 and 59.1 tex:
| Yarn | Count | Length per needle | Weight | Share |
|---|---|---|---|---|
| Face | 30 Ne (19.7 tex) | 4.6 mm | 105.2 g/m² | 39% |
| Tie-in (binder) | 100 den (11.1 tex) | 3.1 mm | 40.0 g/m² | 15% |
| Fleecy (pile) | 10 Ne (59.1 tex) | 1.8 mm | 123.5 g/m² | 46% |
| Total, grey | 268.7 g/m² | 100% |
The shares depend only on the yarns and lengths, so they hold at any stitch density. The paper gives no stitch density. Its grey weight implies 114 to 118 needle loops per square centimetre. The link uses 7.9 wales per cm, the machine’s needle spacing of 1.27 mm, and 14.7 courses per cm to land inside that range. The coarse fleecy yarn is short per needle, yet it carries nearly half the weight. The tool’s note says brushing sheds fibre, so a brushed fabric weighs less than this. Finishing can go the other way: in this paper the fabric narrowed and its weight rose at every stage, to 337–342 g/m² after compacting.
Ignore the tool’s pile-height figure for this fabric. It reads -1.40 mm because it assumes a looped pile (terry or plush), where pile height comes from the extra loop length. In three-thread fleece the fleecy yarn is floated, not looped, and the pile is fibre raised out of the floats.
Worked example: what the raising rollers do
The raising calculator at its default settings takes a 1.25 m cylinder at 20 rpm with 0.07 m rollers. The pile rollers turn at 1,400 rpm and the counter-pile rollers at 900; the cloth runs at 18 m/min over a 300° wrap, in two passes. These are the tool’s starting values, not a mill’s recipe. The cylinder surface runs at 78.5 m/min, so the roller assembly sweeps the cloth at 60.5 m/min before the rollers turn at all. The pile rollers add their own speed, for a pile slip of 368.4 m/min. The counter-pile rollers subtract theirs, giving -137.4 m/min, where the minus sign means they work against the cloth. The pile-to-counter-pile balance is 2.68. Each point of cloth spends 10.9 s under the rollers and takes 67.0 m of wire travel per pass, 134.0 m in two.
Now slow the counter-pile rollers. Below 275 rpm their slip turns positive: at 250 rpm it is +5.6 m/min, and both roller sets raise (see the same run with counter-pile rollers at 250 rpm). That is the balance the Sistig patent calls hard to find. The tool covers raising only: it has no shearing inputs, despite its address.
Fleece vs sherpa vs French terry vs velour
| Fabric | How it is made | The surface | Source |
|---|---|---|---|
| Fleece (two-end, three-end) | Jersey face; pile yarn held as floats on the back, then napped | Smooth face, soft raised back | Cotton Works |
| Polar fleece (double velour) | Reverse-plaited terry; loops on the back; raised on both faces, sheared, heat set | Pile on both sides | US 6,779,368 |
| French terry | The two-end fleece structure, not napped | Smooth face, uncut loops on the back | Cotton Works |
| Knitted velour | Terry loops cut open by shearing, not brushed | Short upright cut pile | US 6,131,419 (cut-loop fabric) |
| Sherpa | No standard or patent definition found; the name is used for deep-pile fabrics. Deep-pile knits that imitate fur are made by knitting fibre sliver into a ground yarn, then shearing and polishing | Deep pile on one face | US 8,397,542, Kaneka (sliver-knit pile) |
A woven terry has loops on both faces and stays looped; see terry towels.
Fleece weights: 100, 200, 300 and GSM
Polartec sells its fleece in four weights: Micro, 100, 200 and 300. It describes them as ultra-lightweight, lightweight, mid-weight and heavyweight, but gives no g/m² (Polartec, Fleece Series). The figures below come from Polartec’s own listings on the Performance Days fabric marketplace, which marks them as supplier-provided.
| Fabric | Weight class | g/m² | Fibre |
|---|---|---|---|
| Polartec Micro 6125RC, micro velour | Micro | 159 | 100% recycled polyester |
| Polartec 100 Series 6180, double velour | 100 | 193 | 80% recycled, 20% polyester |
| Polartec 200 Series 6213RC | 200 | 251 | 100% recycled polyester |
| Polartec 200 Series with Shed Less, 9280US | 200 | 258 | 100% recycled polyester |
| Polartec 300 Series | 300 | no listing found | – |
| Three-thread fleece, Hossain et al., after compacting | – | 337–342 | Cotton fleecy yarn, polyester-cotton face |
The class number is a name, not a measurement. A heavier knit with a lower pile can outweigh a lighter, loftier one. To estimate a knit’s weight from its yarn and loop length, use the knitted fabric GSM predictor.
Pilling and anti-pill fleece
Pills form when fibre ends stick out of a fabric and wear rolls them into balls. Polyester pills stay on because polyester fibres are strong, so the balls cannot drop off. Low-pill polyester is made deliberately weaker, which lets the pills break away (US 7,189,794, Trevira). DuPont found its fabric’s pill rating improved as the polymer’s viscosity was lowered (US 5,817,740). A fleece patent states the problem plainly: fleece made of polyester, with its high strength and extensibility, pills easily (US 7,213,313).
Finishing helps too. Hossain and co-authors tested their three-thread polyester-cotton fleece in an ICI pilling box to ISO 12945-1:2000, for 14,400 revolutions. Untreated fabric rated grade 1, the worst. With heat setting at 190 °C and singeing, it rated grade 4 (Heliyon, 2021). Any “anti-pill” label is a claim to check against a test like this:
- ISO 12945-2:2020, the modified Martindale method (catalogue entry), and ISO 12945-4:2020, the visual assessment. Its scope names napped fabrics, “fleeces, inlay fabrics” (catalogue entry).
- ASTM D4970/D4970M, pilling on the Martindale tester, and ASTM D3512/D3512M, the random tumble pilling tester.
To compare pill counts taken over different numbers of cycles, use the site’s pilling propensity calculator. The visual grade remains the contractual result.
Fleece and microfibre shedding in the wash
Pirc and co-authors washed six new polyester fleece blankets, each about 320 g. The fabric was a weft-knitted base with loop piles of about 1 dtex microfibre. They washed for 15 minutes at 30 °C in a front-loader and filtered the waste water at 200 µm (Environ. Sci. Pollut. Res. 23, 22206–22211, 2016). The first wash released 0.008–0.021% of the fabric’s mass, 25.6 to 67.2 mg for one blanket. Over later washes release settled near 0.0012% a wash. Detergent and softener made no significant difference, and tumble drying released about 3.5 times as much as washing.
At that settled rate, the microfibre release calculator gives 3.84 mg a wash and 192 mg over 50 washes, 0.06% of the blanket. That is a floor, because the higher first washes are left out. Hartline and co-authors found far more from jackets and sweaters, four of them fleece, in home machines, washing without detergent and filtering down to 20 µm. Up to about 2 g came from one garment in one wash, more than 0.3% of its mass. Top-loaders released about seven times as much as front-loaders, and garments aged by a 24-hour wash released more than new ones (Environ. Sci. Technol. 50, 11532–11538, 2016). A wash that sheds 0.3% of a 320 g blanket, 0.96 g, is about 5 times the 50-wash total above. The test method decides the result. ISO 4484-1 now standardises the collection (ISO 4484-1:2023), and its scope warns that results do not correlate directly with domestic laundering. Polartec says its Shed Less fleece cuts shedding by up to 85% on average in home laundering; that is the maker’s claim (Polartec). More on the wider problem: microplastics from synthetic fabrics.
Recycled fleece
Polartec dates the first fleece with recycled content to 1993, launched in “Soda-Bottle Green”, the colour of the bottles. It moved its whole product line to fabrics with recycled content in 2007, after development work with Unifi (Polartec, About). Today it says most of its fleece is post-consumer recycled polyester from water bottles (Fleece Series). How bottles become fibre is on the polyester fibre page, and the limits of recycled yarn are on recycling and re-spinning post-consumer fibres.
A short history of polar fleece
Polartec traces itself to Malden Mills, which it says has made textiles for over 100 years. Its own timeline begins with “The synthetic fleece is born” in 1981. Then come Patagonia’s Synchilla Snap-T pullover in 1985, Polarfleece prints on European ski slopes in 1986 and the Polartec brand in 1991 (Polartec, About). The Victoria and Albert Museum holds a Snap-T. Its record dates the design to 1985 and describes Synchilla as a softer, double-faced fabric developed with Malden (V&A, Snap-T Fleece). Accounts that date polar fleece to 1979 cite no primary source this page could find.
Caring for fleece
- Follow the label. Care symbols are standardised in ISO 3758; the garment’s own label sets the limits.
- A front-loader sheds less. In Hartline’s tests, top-loaders released about seven times the mass (2016).
- Line drying sheds less. Pirc’s dryer released about 3.5 times what the wash did (2016).
- Softener made no difference to shedding in Pirc’s tests. Whether it suits a particular fabric is the label’s call.
- Pills on polyester fleece stay put. Remove them; they will not wash off. A worn fleece also sheds more: Hartline’s garments, aged by a 24-hour wash, released more fibre.
Questions about fleece fabric
Is fleece knit or woven?
Polar fleece and the fleeces Cotton Incorporated describes are knitted: a jersey face with yarn floated or looped on the back, then raised. Woven pile fleece also exists (US 7,213,313).
What is the difference between double knit and fleece?
A double knit is knitted on two needle beds, so both faces are knitted surfaces. Fleece is a single-jersey face with a raised back, so its two sides differ. Polar fleece is the exception: it is raised on both faces. See knit structures.
Is a polyester fleece blanket the same fabric as a fleece jacket?
It can be. Pirc’s test blankets were a weft-knitted polyester base with microfibre loop piles (2016).
What is the difference between cotton fleece and polyester fleece?
Cotton fleece has a cotton or cotton-rich back yarn, as in Hossain’s fleece with its 100% cotton fleecy yarn. Polar fleece is all polyester. Cotton Incorporated lists all three blends: all cotton, cotton and polyester, and all synthetic.
What is microfleece?
The lightest class. Polartec calls its Micro “ultra-lightweight” and lists one at 159 g/m². Pirc’s fleece blanket used microfibre of about 1 dtex for its pile.
How this page is kept
Last verified: 17 October 2026. Construction comes from the patents of the companies that made the fabrics and machines, read on Google Patents, and from Cotton Incorporated’s knitting course, read in an archived copy. Weights come from Polartec’s own fabric listings, and shedding and pilling figures from peer-reviewed papers, each cited where it is used. The worked examples are computed in the site’s calculators; this page’s figures are generated by the same formulas when it is built. The page describes fabrics in general; it is not a specification, and a garment’s own label and test reports take precedence. Corrections are welcome through the contact page.
