One brand orange, three substrates, one tolerance
A beverage brand specifies its signature orange only as Pantone Orange 021 C, with a tolerance of ΔE00 ≤ 2.0 against the master chip. The colour appears on three substrates in one campaign: a 350 gsm GC1 one-side coated carton printed offset with a spot ink plus CMYK; a 90 gsm uncoated label printed offset; and a 1,200-copy short run of the same label on a dry-toner digital press with CMYK plus orange, green and violet. On press, the carton first-off measures ΔE00 1.1 against the chip. The uncoated label, from the same ink batch, measures 3.9 and reads dull and brownish. The digital label measures 4.6 and reads flat. The foreman proposes raising ink density on the uncoated stock until it matches the chip; the brand owner refuses to change the master; the job ships in five days. The lab measures with a 45/0 spectrophotometer, D50, 2° observer, M1.
1. Explain why the same ink cannot deliver the same measured result on coated and uncoated stock, and why raising density on the uncoated label is the wrong remedy.
Read the worked answer
The chip is a printed patch on coated stock, so the number in the brand manual is a substrate-specific target, not a property of the ink. On coated board the film sits on a sealed surface: high holdout, thick effective film, high gloss, high chroma. On uncoated stock the vehicle is absorbed into the pore structure, pigment packs closer to the surface with less binder above it, and the substrate's own shade and optical brighteners show through a transparent orange. The result is lower chroma at the same ink film weight, plus a darker, browner appearance under M1 because UV excitation of the base is suppressed.
Raising density adds film weight but cannot restore holdout. It pushes the colour toward brown, raises the risk of set-off and back-trapping on a 90 gsm sheet, slows drying, and may bring total ink coverage to a level the stock cannot take. You could bring ΔE00 down slightly while failing on hue and on setting, which is a worse outcome than a documented, agreed uncoated target. The correct path is a second target for that substrate, not a denser print.
2. Set out the measurement and target protocol you would use for each of the three substrates so that the ΔE00 ≤ 2.0 clause can be enforced or formally varied.
Read the worked answer
Measurement
- Instrument: 45/0, D50, 2° observer, M1 (UV included), because the uncoated stock contains optical brighteners.
- Patch: solid 100% area of at least 6 × 6 mm, measured in a position representative of the run, on the production substrate, over the same backing used for the approved target (white backing for opaque cartons, the production label backing for labels).
- Average three readings, record Lab*, ΔE00 and ΔH, and keep the measurement position marked on the approved sheet.
Targets
- Carton: the master chip, measured in the lab on the same instrument. Continues at ≤ 2.0.
- Uncoated label: no chip on that substrate exists, so derive and sign off a second target from a printed uncoated reference, and widen the tolerance to something achievable, for example ΔE00 ≤ 3.0 with ΔH ≤ 1.5. Put it in writing as a brand variant before the run.
- Digital label: same agreed target as the uncoated variant, but verified through the device's ICC profile and a printed patch on that machine.
Without the written variant, every uncoated and digital delivery fails the contract while the print is commercially correct, and the argument lands on the printer.
3. The brand will not relax the tolerance and will not print the digital run by another process. What are your options for the 1,200-copy digital label, and how do you verify the chosen one?
Read the worked answer
First test whether the target is inside the device gamut: convert the agreed Lab* target through the digital press ICC profile and compute the predicted ΔE00. A dry-toner CMYK-only build for a clean orange typically lands outside gamut on the yellow/red edge, which is exactly what the 4.6 reading shows.
Options, in order of preference:
- Use the OGV channels properly. Build the orange as a controlled combination of Y/M plus a small orange channel rather than a CMYK approximation, and keep total area coverage within the machine's limit. This often pulls ΔE00 under 2 on a 1,200-copy run.
- Print the label as a hybrid job - digital for the variable or short part, one spot screen or offset pass for the orange - if the schedule allows a second pass on a different machine.
- Move the short run to a device with a wider gamut (inkjet or a press with an extended-gamut ink set) if the first two fail.
Verification: print a test sheet with the target patch and the actual label, measure five positions across the sheet, confirm ΔE00 ≤ 2.0 and uniformity within ΔE00 1.0, then have the approved sheet signed and retained as the run reference.