Last updated: October 2026
Quick answer: Flexo dot gain (tone value increase) is the difference between the dot size in the file and the printed dot. It comes from the plate, anilox, impression, mounting tape, ink and substrate together. Gain is normal in flexo and higher than in offset. Control it by stabilising the press, measuring a fingerprint with a densitometer or spectrophotometer, and applying a compensation curve in prepress.
Key takeaways
- Dot gain is a system result: plate, anilox, impression, tape, ink and substrate all contribute.
- Gain is highest in highlights and mid-tones and is normal in flexo; the target is stable, known gain.
- Measure tone value increase on a test form under fixed press conditions (a fingerprint).
- Correct gain with a compensation curve per plate, press and substrate combination.
- Change the plate type only after the press is stable, or you will chase the wrong cause.
The complaint usually arrives from the customer first: highlights print much darker than proof, colours drift from proof, or vignettes break into a hard edge. Under pressure, many printers assume dot gain is just the plate’s fault and that a new plate will fix the colour. Sometimes the plate is part of the story, but flexo dot gain is a system effect. This guide explains where gain comes from, which plate and press factors you can control, how to measure gain properly and how to bring it under control. It is written for prepress managers and press supervisors in packaging and label plants.
Flexo dot gain in brief
Dot gain, more correctly called tone value increase (TVI), is the difference between the tone value in the file and the tone value measured on the print. A 50% dot in the file that measures larger on the print has gained. Gain has two parts: mechanical gain, where the dot physically spreads under pressure and ink squeezes out, and optical gain, where light scatters inside the substrate and makes dots look larger.
Flexo has more mechanical gain than offset because the plate is soft, the ink is fluid and the plate prints directly onto the substrate. That is why dot gain must be managed in flexo, not eliminated. The goal is gain that is stable from job to job and can be corrected in prepress.
Where flexo dot gain comes from
| Source | Effect on gain | What you can control |
|---|---|---|
| Plate | Dot size and shape, durometer and relief change how dots deform | Plate type, gauge, exposure, relief |
| Anilox | Too much ink volume floods dots; coarse ruling lets small dots dip into cells | Cell volume and ruling per job |
| Impression | Extra pressure squashes dots and spreads ink | Kiss impression, set by operator |
| Mounting tape | Hard tape transmits more pressure to highlights | Tape density per job type |
| Ink | Low viscosity and high ink film spread more | Viscosity and pH control |
| Substrate | Absorbent and rough substrates increase optical and mechanical gain | Substrate choice, priming or coating |
Plate factors that affect dot gain
The plate is one controllable part of the system:
- Imaging method. Digital LAMS plates hold smaller highlight dots than analog plates; see analog vs digital flexo plates.
- Dot shape. Round-top dots grow as impression rises; flat-top dots keep a more stable printing area. Read flat-top vs round-top flexo dots.
- Plate durometer and gauge. Thinner, harder plates usually give less gain on smooth film; thicker, softer plates give more but conform to rough board.
- Relief and floor. Fine dots on very deep relief can flex and gain unevenly; see flexo plate relief depth.
- Exposure consistency. Lamp ageing changes dot size on the plate itself, which shows up as drifting gain.
Our digital flexo plates are the usual choice for process colour work where gain must be tight, and our flexo plate range covers analog and corrugated grades as well.
Press factors: anilox, impression, ink and substrate
Anilox. The anilox roll meters the ink film. If cell volume is too high, dots are flooded; if the anilox ruling is too coarse compared with the plate screen ruling, small dots can dip into the cells and pick up extra ink. Typical in the industry, the anilox ruling is chosen several times finer than the plate screen ruling, often in the range of about 4 to 6 times. Your ink and anilox supplier can confirm the right specification.
Impression. Over-impression is the most common cause of sudden gain on press. Set kiss impression: just enough pressure for full solids, no more. Mark the settings so the next shift starts from the same point.
Mounting tape. Softer foam tape absorbs pressure in highlights and reduces gain; harder tape gives better solids. Many process jobs use different tape for line and process plates. See flexo plate mounting. We can also supply mounting tape, sleeves and anilox rolls with your plate order; ask in your quote request.
Ink and substrate. Ink viscosity drifts during the run as solvent or water evaporates, so control it at regular intervals. Uncoated paper and kraft board gain more than film or coated board.
How to measure flexo dot gain
Measure on a standard test form with tone patches (for example 2, 5, 10, 25, 50, 75 and 95 percent tints, plus solid) for each colour:
- Stabilise the press: correct anilox, tape, kiss impression, ink viscosity and speed.
- Print the test form on the production substrate without any compensation curve (linear plates).
- Measure each patch with a densitometer or spectrophotometer and record tone value.
- Tone value increase = measured tone value minus file tone value, for each patch.
- Repeat on several sheets or metres and average the results.
This set of measurements is the press fingerprint. International standards such as ISO 12647-6, the part of the ISO 12647 series for flexographic printing, describe how tone value increase is specified and measured; many brand owners refer to it in their print specifications. For recording plate-side results, use our plate test protocol.
How to reduce and control dot gain
- Fix the press first. Anilox, impression, tape and ink control remove most unstable gain.
- Fingerprint each combination. Plate type, press, anilox set and substrate group.
- Build a compensation curve. The RIP reduces dot sizes on the plate so the printed result matches the target. Set a minimum highlight dot that the plate holds reliably.
- Lock plate making. Fixed exposure, relief and processing settings per TDS; log lamp hours.
- Re-check regularly. Repeat the fingerprint after changes in plate grade, anilox, tape or substrate.
Printers often object that they have no time for a fingerprint. A fingerprint takes a few hours of press time; colour complaints and reprints usually cost far more. Done once and kept up to date, it gives print that matches the proof, smooth vignettes to zero and fewer colour complaints.
Dot gain troubleshooting table
| Symptom | Likely cause | What to check |
|---|---|---|
| Highlights much darker than proof | Over-impression, hard tape, no curve | Kiss impression, tape density, compensation curve |
| Vignette breaks to a hard edge | Minimum dot not held or too large | Minimum dot in curve, plate exposure, dot shape |
| Gain grows during the run | Ink viscosity rising, plate swelling | Viscosity control, plate and ink compatibility |
| Gain differs across the web | Uneven impression or worn anilox | Impression parallel, anilox condition |
| Gain changes between plate sets | Exposure or processing drift | Lamp hours, relief, TDS settings |
| Dirty print, filled shadows | Too much ink volume, low relief | Anilox volume, relief depth |
If you suspect the plate, send us your measurements; our technical support team will review them with you before any plate change.
FAQ
What is dot gain in flexo printing?
Dot gain, or tone value increase, is the difference between the dot size in the file and the measured dot on the print. In flexo it comes from dots spreading under pressure and from light scattering in the substrate, and it is normally higher than in offset.
What causes dot gain in flexography?
The main causes are excess impression, anilox volume and ruling, mounting tape hardness, ink viscosity, substrate absorbency and plate factors such as dot shape, durometer and relief. Gain is a result of the whole system, not one part.
How do you reduce dot gain in flexo printing?
Stabilise the press first with kiss impression, a suitable anilox, the right mounting tape and controlled ink viscosity. Then print a fingerprint and apply a compensation curve in prepress, with plate making locked to the TDS settings.
How is flexo dot gain measured?
Print a test form with tint patches on the production substrate without a curve, measure each patch with a densitometer or spectrophotometer, and subtract the file value from the measured value to get the tone value increase.
What is a flexo compensation curve?
A compensation curve is a correction applied in the RIP that makes plate dots smaller so the printed tone matches the target after gain. It is built from a press fingerprint and must be redone when the plate, anilox, tape or substrate changes.
Fighting dot gain or changing plate grade? Request a quote with your press type, anilox and tape, ink system, substrate, screen ruling and current measurements. Or request trial plates / contact us.
Disclaimer: values on this page are typical and for reference only; final specifications, MOQ, price and lead time are subject to the grade TDS and the quotation.
