Flexo dot gain: TVI, compensation curves, and repeatable press conditions

Flexo dot gain is the increase between a tint value in the source file and the tone value measured in print. The preferred technical term is tone value increase, or TVI.

X-Rite gives a simple example: if a 50% control patch measures 68% in print, the TVI is 18 percentage points. That number is not automatically a defect. The real question is whether the result matches the target curve for the approved press condition.

Dot gain is measured against a defined condition

A useful TVI target is not a universal flexo number. It belongs to a defined production condition that includes the press, substrate, ink, anilox, plate, screening, mounting tape, impression, and other controlled settings.

The Flexographic Technical Association describes the traditional workflow this way: print tonal scales during a press fingerprint, measure the result, compare it with the selected aim curve, then calculate an adjustment curve for the plate output.

That distinction matters:

• The fingerprint describes how the condition prints.
• The compensation curve changes plate output so the printed result reaches the aim.
• Production control checks whether the condition still behaves like the fingerprint.

A curve can correct predictable tonal behavior. It cannot make an unstable press condition repeatable.

Compensation and troubleshooting are different jobs

If the same controlled condition repeatedly produces the same tonal response, a prepress curve can compensate for it. If TVI moves during production or between reruns, investigate the condition before changing the curve.

Common causes of a changed result include:

• Impression pressure. More pressure deforms the flexible plate and can enlarge printed dots.
• Plate and mounting package. Plate family, surface, gauge, relief, hardness, tape thickness, and tape hardness change how the image meets the substrate.
• Ink and anilox. Ink strength, viscosity, transfer, anilox volume, and cell condition affect the ink film reaching the plate and substrate.
• Screening and minimum dot. Line screen, screen type, highlight structure, and the minimum printable dot set the tonal structures the plate must hold.
• Substrate and press stability. Surface, absorbency, tension, speed, temperature, and mechanical condition can move the printed response.

Do not use a new compensation curve to hide a worn plate, changed anilox, excess impression, or uncontrolled ink. That creates a curve for the problem instead of restoring the approved condition.

A practical dot-gain workflow

1. Define the print condition. Record the press, substrate, inks, anilox rolls, plate system, screening, tape, and intended production settings.
2. Optimize before fingerprinting. Establish stable ink transfer, impression, registration, drying, and mechanical settings.
3. Print and measure a controlled target. Include solids, tone scales, gray balance, overprints, highlights, and other relevant test elements.
4. Choose the calibration method and aim. Traditional TVI curves use measured tone scales. Near Neutral Calibration or G7 also evaluates gray balance. SCTV provides a colorimetric tone-value method for spot colors.
5. Build and verify the plate curves. Apply the calculated curve set, make verification plates, and confirm that print falls within the approved target and tolerance.
6. Monitor production. Measure the same control points during production and separate normal variation from a real change in the condition.

Density alone is not enough to prove color is correct. X-Rite notes that a press can reach the expected solid density while tone value, overprint, or ink color is still wrong. Use the measurement method that matches the process-control goal.

What belongs on the job record

For reliable reruns, keep the curve with the condition that validated it:

• curve name, version, target method, and approval date;
• press, substrate family, ink system, and color sequence;
• anilox identity, line count, volume, and condition;
• plate family, gauge, screening, minimum dot, and imaging setup;
• mounting tape family, thickness, and hardness;
• fingerprint and verification measurements, tolerances, and approved sample;
• operator, equipment, production date, and any approved exception.

If a substrate, plate, tape, anilox, or press changes, the old curve may no longer describe the job. A flexo-native MIS keeps the approved curve and measurement evidence beside the customer and job specification so prepress and the plate room can see whether a rerun still matches the validated print condition.

The short version

Flexo dot gain is TVI, the difference between a source tint and the printed tone value. Measure it on a controlled target, compensate predictable behavior with a curve, and troubleshoot condition drift before changing that curve. Store the curve with the press, plate, tape, anilox, ink, substrate, and verification data that made it valid.

Flexo dot gain FAQ

What is dot gain in flexographic printing?

Dot gain is the increase between a tint value in the source file and the tone value measured in print. A 50% file tint that measures 68% in print has 18 percentage points of TVI.

How is flexo dot gain measured?

Print a controlled tone scale under a defined press condition, measure its tint patches with a densitometer or spectrophotometer using the selected method, and compare the printed values with the source values and approved target curve.

What causes excessive dot gain in flexo?

Common causes include excess impression, a changed plate or mounting package, ink or anilox changes, unstable press conditions, and a compensation curve built for a different substrate or production condition.

Should every flexo job use the same dot-gain curve?

No. A curve belongs to the production condition used to create and verify it. Reuse it only when the relevant press, substrate, ink, anilox, plate, screening, tape, and production settings still apply.

Sources and related reading

• FTA: TVI, NNC and CIE Lab color management — fingerprinting, measured tone scales, TVI adjustment curves, and gray-balance calibration.
• X-Rite: Establishing flexo process control — production targets, press fingerprinting, control patches, and condition-specific measurements.
• X-Rite: Measuring density with a densitometer — TVI definition, the 50% to 68% example, density limits, and SCTV.
• FTA: Natural Plate Compensation Curves for Flexography — plate compensation based on ISO 20654 SCTV measurements.
• Flexo minimum printable dot — how minimum-dot, bump, and cutoff settings interact with the print condition.
• Flexo printing defects — a practical plate-versus-press troubleshooting method.
• Anilox line screen selection — how anilox volume and line count constrain plate screening and tonal control.