Ponte Roma (double knit) development: from yarn to tested fabric

A step-by-step development guide for Ponte Roma: the four-feeder interlock-based structure, polyester/viscose and elastane yarns, heat setting, two-bath dyeing, pilling control, GSM and width, and testing, built on our development records and labelled typical practice.

Ponte Roma, also written Ponte di Roma and often sold simply as “double knit”, is the stable, heavy knit behind tailored trousers, pencil skirts, sheath dresses, school and office wear and soft blazers. It has the body of a light woven but still stretches like a knit. It is knitted on an interlock machine with a four-feeder repeat, and is very often made from polyester/viscose yarn with elastane, so you plan a double jersey construction, heat setting and two-dye-class dyeing. This guide follows the route from the buyer’s request to a tested fabric. Our records for ponte are very thin: 16 entries in our fabric register, only two yarn constructions with enough entries for medians, and no lab reports at all. So this guide says plainly where the data stops, and fills the rest with general practice, marked as typical.

What Ponte Roma is

An interlock course plus two single-bed courses

Ponte Roma is a weft knitted double jersey made on a circular machine with a dial and a cylinder in interlock gauging. Each bed has two sets of needles, usually called set 1 and set 2 (or long and short butt), which run in different cam tracks, so each feeder can make one set knit while the other misses. In the most common construction the machine works in repeats of four feeders:

• Feeder 1. Set 1 needles on both beds knit. Because each feeder works on alternate needles of each bed, this is a half-gauge course: a 1×1 rib on half the needles.
• Feeder 2. Set 2 needles on both beds knit. It fills the gaps left by feeder 1. Feeders 1 and 2 together make one full interlock course.
• Feeder 3. All cylinder needles knit and the dial misses. This is a plain single jersey course on the cylinder only.
• Feeder 4. All dial needles knit and the cylinder misses. This is a single jersey course on the dial only.

If interlock is new to you, read the interlock fabric development guide first; ponte is interlock with something added. For the single-bed courses, the loop basics in the single jersey development guide apply directly.

The two single-bed courses are the heart of the fabric. Between two interlock courses, the cylinder course and the dial course are not connected to each other, so they form a thin, flat tube. Repeated all down the fabric, these tubes act like small pockets. They add thickness and weight without making the fabric open, and they hold the wales apart so the fabric does not narrow much when it is pulled in length. Both faces look alike: fine and smooth, often with faint horizontal lines. Other set-outs exist, so always ask for the cam chart of the machine you are using.

Properties you must design around

• Stability. Ponte stretches less in width than interlock and much less than single jersey, and it recovers well. That is why it can be cut and sewn like a light woven for structured garments.
• No curling and low spirality. The structure is balanced between the two beds, so cut edges lie flat and wales stay straight.
• Weight and thickness. With the same yarn and similar stitch length, ponte is heavier and thicker than interlock, because each needle knits two loops per four-feeder repeat and the pockets add bulk. Typical ponte runs from about 250 to 400 GSM.
• Pilling. Ponte is usually made from spun blends such as polyester/viscose. Spun polyester fibre holds pills on the surface, so pilling is the most common quality complaint on this fabric. It has its own section below.

Where it is used, and its variants

Ponte goes into smart trousers and leggings, skirts, dresses, jackets and uniform wear. The variants are:

• Polyester/viscose/elastane ponte. The main fashion quality: soft, slightly lustrous, with stretch and good recovery.
• Cotton or cotton blend ponte. A heavier, more matt fabric with a natural handle, often without elastane.
• Viscose with polyester filament. A stretch ponte where the polyester is a filament, not a staple fibre, which helps pilling.
• Yarn-dyed or melange ponte. Knitted from coloured or heather yarns and finished without piece dyeing.

How ponte relates to scuba-like and bonded fabrics

Ponte, knitted double face, scuba-type fabric and laminated bonded fabric are often confused, because all are smooth, firm knits with body. They are built differently, and that decides how you knit and dye them.

So a ponte is one fabric with one yarn system, while a double face has separate yarns for each face and a tie yarn. Our register has no scuba entries, so this guide gives no scuba data. For the knitted double face, see the bonded interlock (double face) development guide; for the wet route of scuba-type fabric, see the scuba fabric dyeing and finishing flowchart.

What our records hold

The register has 16 ponte entries under four type names: PONTE ROMA, PONTI ROMA and the stretch versions L/PONTE ROMA and L/PONTI ROMA. All 16 were finished open width on stenter plus compactor, and 14 of them (88%) carry a heat-set flag. The register’s fibre grouping puts 7 entries in cotton/polyester with elastane, 4 in cotton and 5 in a mixed “other” group. Eleven entries were knitted on 24 gauge, four on 18 gauge and one on 28 gauge; fifteen on a 34 inch machine and one on 36 inch. Only two yarn constructions have enough entries for medians, four entries each. That is a small base, so treat every number below as a pointer, not a standard.

What is ponte knit fabric made of?

Ponte knit (short for Ponte di Roma) is a thick, firm double knit with the same smooth look on both sides. It is a knit, not a woven, but it is stable enough to be cut and sewn like a light woven, which is why it is used for smart trousers, leggings, skirts, dresses and jackets.

Ponte can be made from almost any spun yarn. The common blends are:

• Polyester / viscose / elastane: the main fashion quality, soft with a slight lustre and good stretch and recovery.
• Polyester / viscose without elastane: firmer, used for uniforms and structured pieces.
• Cotton or cotton blends with elastane: softer and more breathable, but less stable in size.
• Modal or viscose-rich ponte: very soft drape, but needs more care with shrinkage.

What makes ponte ponte is the construction, not the fibre: an interlock course followed by one course on each needle bed, which builds small pockets that add thickness without making the fabric open. Most fashion ponte is polyester/viscose based, which is why pilling is its most common complaint.

Development inputs

Read the buyer’s request carefully

Write every requirement in one place before choosing yarn. For ponte the request should state:

• Finished GSM with tolerance, often ±5%.
• Finished width, usually open width in cm.
• Composition, for example a polyester/viscose/elastane split, or cotton/elastane. The label depends on the weight share of each yarn, so it must be worked out, not guessed.
• Stretch and recovery: how much stretch in width and length, and whether a growth or recovery test applies.
• Shade and light source. On a blend, both fibres must reach the same shade.
• Wash care: many ponte garments are labelled for a cool wash or dry cleaning, which changes the test conditions.
• Tests: dimensional stability, GSM, pilling, colour fastness, stretch and recovery, pH and fibre content.

If the buyer says only “ponte, 300 GSM”, ask about stretch and pilling; they decide the yarn.

Choosing the yarn

Polyester/viscose spun yarn. The usual main yarn, in blends such as 65/35 or 70/30, typically from about 30/1 to 40/1 Ne. Polyester gives strength, shape and fast drying; viscose gives softness, drape and moisture comfort. A higher polyester share pills more and feels firmer.

Spinning system. Ring-spun yarn is soft but hairy, and hairiness feeds pilling. Compact yarn is less hairy. Air-jet spun yarn has its fibres wrapped round a parallel core, so it is far less hairy and usually pills less, at the cost of a slightly firmer handle. One of our two main constructions uses 30/1 air-jet spun viscose.

Elastane. Usually 20 to 40 denier, fed bare or as a covered yarn. Some elastane types are made to take dye more readily, which reduces “grin-through” of white elastane when the fabric is stretched; our viscose construction records a 20 denier dyeable type. Elastane is a polyurethane fibre: it tolerates heat only up to a point and is damaged by chlorine and strong alkali, so it limits heat setting and dyeing.

Air-covered yarn. An elastane core entangled with a filament, here polyester, by an air jet at intervals. It feeds like a filament and hides the elastane better than bare feeding. Our viscose construction records a 75 denier air-covered polyester.

Cotton. Combed ring or compact yarn; our cotton construction uses 20/1 and 26/1 on 18 gauge.

Common mistake: choosing a cheap ring-spun polyester/viscose yarn for a ponte that the buyer will test for pilling. The fabric looks perfect at approval and fails after rubbing. Choose the yarn for the pilling test first, then for price.

Knitting

Gauge and diameter

Ponte in our records is knitted mostly on 24 gauge (11 of 16 entries), with 18 gauge (4 entries) for a heavy cotton quality and one 28 gauge entry. A coarser gauge takes a coarser yarn and gives a heavier, bulkier fabric; a finer gauge a smoother, lighter face.

Diameter decides the width. The number of needles on each bed is diameter × π × gauge, and the open width after finishing is that number divided by the wales per cm on the face.

Worked example. A 34 inch, 24 gauge machine has 34 × 3.1416 × 24 = about 2,564 needles per bed. Our viscose construction finishes at 178.5 cm, which works out at about 14.4 wales per cm. If finishing pulls the fabric in to 15 wales per cm, the width falls to about 171 cm. The same sum for 34 inch, 18 gauge (about 1,923 needles) and our cotton construction’s 158 cm gives about 12.2 wales per cm. (Fifteen of our 16 entries were on 34 inch machines; check the job card.)

Stitch length and GSM

The basic rule is the same as for any knit: GSM is the weight of yarn in one square metre. For a single-yarn fabric, GSM = (courses per cm × wales per cm × stitch length in mm × tex) ÷ 100, with tex = 590.5 ÷ Ne. Ponte has more loops to count: in each four-feeder repeat every needle knits twice, once in the interlock course and once in its single-bed course. So the formula must be applied to each yarn and course type and the results added. The knit GSM from stitch length calculator and the GSM calculator show how stitch length or count moves the weight, but for a multi-yarn ponte a knitting trial is the real answer.

A shorter stitch length gives a tighter, heavier, firmer fabric with better pilling; a longer one gives a softer, lighter, more open fabric. Elastane pulls the loops together after knitting, so a stretch ponte finishes much more compact than it looks on the machine.

Two constructions from our records

The table shows the two ponte constructions with enough entries for medians. Stitch length is given as the register writes it; where there are two values, they are the stitch length per yarn as recorded, in yarn order.

The cotton construction is a heavy 350 GSM quality on 18 gauge, with one stitch length of 3.05 mm recorded for both cotton yarns; it finished slightly heavy at 357 GSM and 158 cm wide. The viscose stretch construction is a 290 GSM fashion quality on 24 gauge that finished on target, 289.5 GSM, at 178.5 cm. Both show 2% spirality, low as expected for a balanced double knit.

Knitting points specific to ponte

• Cam arrangement. Set the four-feeder repeat exactly as on the cam chart, and check that the number of feeders on the machine is a multiple of four. A wrong cam in one feeder shows as a repeating line or a band of different handle around the tube.
• Interlock and single-bed courses. The stitch cams for the interlock feeders and the single-bed feeders may be set to different stitch lengths. Measure and record each, because the balance between them changes thickness, weight and width.
• Elastane feeding. Feed elastane or covered yarn from positive feeders at a fixed draft, and keep it the same on every feeder that carries it. Uneven draft shows as bars and as stretch differences across the width. The Lycra single jersey development guide covers draft setting in more detail.
• Barre. One yarn lot per order, and the same yarn on all feeders of the same type. See barre in knit fabric.

Machine settings to record

• Machine number, diameter, gauge, total feeders and the cam chart of the repeat.
• Yarn on each feeder: count or denier, blend, spinning system, lot and supplier.
• Stitch length per yarn and per course type, measured on the greige fabric.
• Yarn input tension, elastane draft, and positive feed setting.
• Take-down tension and machine speed.
• Greige tubular dia, greige GSM and roll weight.

Greige inspection

Inspect for holes, drop stitches, needle lines, elastane breaks, oil stains, barre and wrong-cam lines. Measure greige GSM and dia after the roll has rested. A stretch ponte is narrow and heavy in greige, because the elastane has pulled it in; its size is set later on the stenter. Check that elastane oil spots are not present, because heat setting can fix them into the fabric.

Dyeing and finishing route

All ponte in our register went through an open-width route with stenter and compactor. The route below is the usual one for a polyester/viscose/elastane ponte, with typical parameter ranges. A cotton or viscose ponte without polyester skips the disperse dyeing and the reduction clear. The site’s ponte roma dyeing and finishing flowchart gives a short overview, and the full wet processes are in polyester viscose knit dyeing process and viscose elastane knit dyeing process.

Heat setting elastane blends

Heat setting fixes the elastane and the polyester at a chosen width and length before wet processing. Without it, the elastane pulls the fabric in during dyeing, and it creases and comes out narrow and heavy. In our register 14 of the 16 ponte entries carry a heat-set flag.

• Temperature and time. Typically 180 to 195°C for 30 to 60 seconds of fabric time in the stenter. With viscose in the blend, many dye houses stay at the lower end, about 180 to 190°C, because viscose can yellow and harden at high heat. Elastane loses power if it is set too hot or too long.
• Width and overfeed. Set at, or a little above, the planned finished width, with overfeed to control length. The heat-set width largely fixes the final width and weight, so record it.
• Greige or after a pre-wash. Setting greige is common, but oil and dirt on the greige can be fixed in by the heat. If the greige carries heavy oil or stains, a short pre-scour before heat setting is safer.

Scouring

Polyester/viscose ponte needs only a mild scour, typically 60 to 80°C with a detergent and mild alkali, to remove spinning oil and dirt. Viscose is weaker when wet than cotton and swells strongly in water, so strong alkali, long hot treatments and harsh bleaching are avoided. Cotton ponte is scoured and bleached like other cotton knits; see the 100% cotton knit dyeing process.

Dyeing polyester/viscose/elastane

The polyester takes disperse dye. The viscose takes reactive dye, the same class as cotton (see how reactive dyes work). The usual route has two baths:

1. Disperse dyeing of the polyester. Typically 120 to 130°C at pH 4.5 to 5.5 with a dispersing and levelling agent. With elastane present, many dye houses keep to about 120 to 125°C and a shorter hold time to protect the elastane’s power.
2. Reduction clear. Sodium hydrosulphite and alkali, typically 70 to 80°C for 15 to 20 minutes, removes disperse dye from the fibre surfaces and from the elastane. Elastane takes up disperse dye easily but holds it badly, so this step decides wet rubbing and wash fastness on medium and dark shades. Keep it mild for viscose.
3. Reactive dyeing of the viscose. Typically around 60°C with salt and alkali dosed in steps. Viscose dyes faster than cotton and often needs less salt, so control the start of the dyeing for level results. See level dyeing and uneven shades.
4. Wash-off and soaping to remove unfixed reactive dye, then softener.

Shade matching is the hard part. If one fibre is lighter, the fabric looks frosty or skittery, with light flecks. Check the shade after the disperse step and match the reactive shade to it, and keep the recipe and liquor ratio fixed from lot to lot (see shade variation lot to lot). For a cotton/polyester ponte the logic is the same as for CVC; see the CVC fabric dyeing process. For cotton/elastane ponte see the cotton elastane (Lycra) knit dyeing process.

Common mistake: running a heavy viscose ponte in a jet at high reel speed and a tight liquor ratio. Wet viscose is weak and swollen, the fabric is thick, and the result is rope marks and surface fibre rubbed up, which later pill. See crease marks in knit dyeing.

Finishing

• Softener. Typically pH 5 to 6 at 30 to 40°C. Some slippery softeners make fibres slide out of the yarn more easily and can worsen pilling, so test the chosen softener on pilling, not only on handle.
• Slitting and de-watering. Slit along a marked needle line and de-water with low tension; ponte is heavy and holds a lot of water.
• Stenter. Typically 130 to 160°C with overfeed, below the heat-set temperature. On dark polyester shades, high stenter heat can draw disperse dye to the surface (thermomigration) and lower rubbing fastness.
• Compactor. Steam and overfeed compress the length. Avoid very hot, hard compaction on polyester-rich ponte, which can leave a shiny, glazed face.

Pilling: why PV ponte pills and what helps

Rubbing pulls fibre ends to the surface, they tangle into a small ball, and the ball either breaks off or stays. Cotton and viscose anchor fibres are weak, so pills tend to break off; spun polyester fibres are strong, so pills stay. That is why polyester/viscose ponte, especially ring-spun with a high polyester share, so often fails pilling.

The controls are mostly in the yarn and construction:

• Polyester type. Low-pill polyester staple fibre, which has lower strength so pills break off, or polyester filament in place of staple.
• Yarn. Air-jet spun or compact yarn instead of ring-spun; slightly higher twist.
• Construction. A shorter stitch length and a tighter fabric hold fibres in.
• Processing. Shorter, gentler jet cycles. Singeing (with care, because polyester melts) or an enzyme treatment on the viscose removes surface fibre; an anti-pilling finish can help a little.

Test pilling with the method the buyer specifies, usually the Martindale or the pilling box, as described in how to test pilling (box and Martindale). Many of the causes and remedies in pilling test fail causes and remedies apply to ponte too, apart from the brushing points.

Hitting finished GSM and width

What our records show

Ponte hits its weight better than most knits in our register. Across all 16 entries the median finished GSM is 1.9% below the required GSM. Eleven entries (69%) finished within ±5% of the target, three (19%) were more than 5% light and two (12%) more than 5% heavy. Compare that with cotton single jersey, which in our records finishes a median 5% light. The stable structure and the heat setting both help: once the width is set, the fabric has little room to move.

After-wash GSM gain and shrinkage

The dye-house wash test tells a different story. After that wash the GSM rises by a median 9.3% (16 entries). In the two main constructions, 357 rose to 383 GSM and 289.5 to 324.5 GSM. The rise comes from relaxation shrinkage. The cotton construction shrank 2% in length and 5% in width; the viscose stretch construction 5% in length and 2% in width. With four entries each these are only pointers, but they make sense: heavy cotton stretched in width on the stenter gives it back when washed, and elastane pulls the stretch construction together in length.

Remember that these are dye-house wash test values from the register. The buyer’s lab shrinkage test is a separate test with its own method and limits, covered in the testing section.

Why the fabric moves

• Viscose swells and relaxes strongly when wet, giving back length stretched in during processing.
• Elastane recovers any stretch left after the stenter.
• Stenter width. Setting wider than the heat-set width makes the fabric lighter now and shrinks it later.
• Compaction. Too little compactor overfeed leaves length in the fabric, which keeps finished GSM low and length shrinkage high.

You can estimate the effect of shrinkage on garment size with the fabric shrinkage calculator, and compare fibres in our knit GSM and shrinkage by fibre study.

How to plan greige GSM and dia

1. Start from the closest construction in the table, or from interlock records for the same yarn if there is no ponte match.
2. Decide the heat-set width first; it fixes most of the finished width.
3. Knit a short trial, record greige GSM and dia, and run it through the full bulk route, including heat setting.
4. Measure finished GSM, width and the GSM after the wash test. If finished GSM is right but after-wash GSM rises a lot, improve relaxation and compaction rather than changing the knit.
5. Write the greige-to-finished ratios on the record sheet.

Worked example. A buyer asks for a 290 GSM stretch ponte. Our viscose construction on 24 gauge finished at a median 289.5 GSM, which is on target, but its GSM after the wash test was 324.5, about 12% higher, and length shrinkage was -5%. If the buyer tests GSM and shrinkage after washing, that construction needs better relaxation before dispatch: more compactor overfeed and a stenter width no wider than the heat-set width. Re-test after each change, one change at a time.

Testing the developed fabric

No lab reports on ponte reached our desk, so we cannot give pass or fail figures for this fabric. The requirements below are typical values; they vary by buyer and end use, so work from the buyer’s own test manual.

Test pilling and stretch-recovery first, because they are tied to the yarn and hardest to fix after knitting; then dimensional stability and GSM after the buyer’s wash. The method guides are:

• How to test shrinkage of knit fabric and shrinkage test fail: causes and remedies
• How to test GSM of knit fabric and GSM test fail: causes and remedies
• How to test spirality of knit fabric and spirality test fail
• How to test bursting strength and bursting strength fail
• Wet rubbing fastness fail: causes and remedies

Development record sheet and troubleshooting

Record sheet template

Use one sheet per trial and keep the requested and actual values side by side. For ponte, the cam chart and the heat-set conditions are as important as the yarn.

Troubleshooting

When a trial misses, start with the most likely cause and change one setting at a time.

Choose the yarn for pilling and stretch, set the cam chart with care, fix the width at heat setting, dye the polyester first and clear it well, and finish below the heat-set temperature. Our 16 records suggest ponte hits its finished GSM well but still gains weight in the first wash, so plan relaxation, and record every trial.

Ponte or scuba? For the smoother, springier polyester-elastane double knit, and scuba vs neoprene, see what is scuba fabric.

Questions

What is Ponte Roma fabric?

It is a double jersey knitted on an interlock machine in a four-feeder repeat: two feeders knit one interlock course, then one feeder knits only the cylinder and one only the dial. The single-bed courses form small pockets that make the fabric thick, firm and stable.

Is ponte the same as scuba or bonded fabric?

No. Ponte is one fabric from one yarn system. A knitted double face has separate face and back yarns joined by a tie yarn, scuba-type fabric is usually a fine polyester/elastane double knit with a smooth filament face, and laminated bonded fabric is two fabrics glued together.

Why does polyester/viscose ponte pill?

Rubbing pulls fibre ends to the surface, and strong spun polyester fibres hold the pills on instead of letting them break off. Low-pill or filament polyester, air-jet or compact yarn, a tighter construction and gentler processing reduce it.

How is polyester/viscose/elastane ponte dyed?

Usually in two baths: disperse dye on the polyester, typically at 120 to 130°C and at the lower end when elastane is present, then a reduction clear, then reactive dye on the viscose at about 60°C. The fabric is normally heat-set before dyeing.

Does ponte hit its finished GSM?

In our 16 records the median finished GSM is 1.9% below required, and 69% of entries finished within ±5%. GSM still rises a median 9.3% after the dye-house wash test, so plan relaxation and compaction.

What is ponte knit fabric made of?

Usually a polyester/viscose blend with a little elastane. Ponte can also be made from cotton, modal or polyester blends. What defines it is the double knit construction, not the fibre.

Kamrul Islam

Textile engineer with 14+ years in dyeing and fabric development. He writes every guide on Dyeing Solution from real production work. Full profile