White Ink and Underprint

A production guide for CMYK + White workflows: object white, white masks, generated underprint, choke/spread, proofs, and common failure checks.

Purpose

This tutorial explains how to decide when white ink is required, how to configure it in Label Studio Creator, and how to validate white plates before printing.

It applies to OKI CMYK + White workflows, external RIP packages, and any production route where white is treated as a fifth color or separation.

White inkUnderprint White maskChoke SpreadTransparent media Dark mediaSeparation proof

1. Decide whether white is needed

Media	Recommended white strategy	Reason
White paper or white PP	Usually no white layer.	The substrate already provides the white background.
Transparent film	White underprint below CMYK, plus optional white objects.	CMYK inks are translucent and need a white base.
Black or colored media	Object white and selective underprint.	White areas and color opacity must be built intentionally.
Metallic media	Selective underprint only where metallic effect should be blocked.	Leaving parts without white preserves metallic shine.
Kraft / textured media	Partial underprint for logos and barcodes.	White improves contrast where needed while preserving the substrate look.

2. Choose the right white mode

Print in white

The selected object is printed as white ink. Use it for white text, logos, symbols, or decorative graphics.

Use object as white mask

The object defines a white separation but does not need to appear as CMYK artwork.

Generate underprint

The app creates white below visible CMYK artwork. Use this for transparent or dark media.

Exclude from underprint

Use this when part of the artwork should remain transparent, metallic, or substrate-colored.

3. Understand choke and spread

White and CMYK registration is never perfectly mathematical on a real press. Choke and spread compensate for this.

Choke: makes the white shape slightly smaller.
Spread: makes the white shape slightly larger.
No adjustment: best when registration is stable and halos are not visible.

Start conservative: small choke values are safer than large changes. Always test physically.

4. Build a clean white layer

White separations should be simple and intentional.

Prefer vector masks for logos, text, and flat shapes.
Avoid noisy white masks generated from compressed images.
Lock white mask objects to prevent accidental movement.
Name layers or objects clearly when possible.
Preview the white plate before sending the job.

5. Proof before printing

White Plate Proof

Shows only the white separation. It must match the intended mask or underprint.

CMYK Plate Proof

Shows process color plates and helps confirm that CMYK is not accidentally encoded as white.

Separation Proof

Shows CMYK, white, and spot separations together for production review.

RIP Package

Use when the job must carry white, spot, ICC, and print intent metadata to an external production workflow.

Stop condition: if the white proof looks wrong, the print will be wrong. Fix the document before testing on media.

6. Common mistakes

Problem	Likely cause	Fix
White halo around artwork	White layer is too large or registration shifted.	Use choke, simplify mask, run a short physical test.
CMYK is dull on transparent media	No white underprint below process color.	Enable generated underprint or create a white mask.
Transparent window becomes opaque	Underprint generated below an area that should stay clear.	Mark object as excluded from underprint or remove white mask there.
Small white text fills in	White density or object size is too aggressive.	Increase font weight/size, reduce density, test on media.
Barcode fails on dark media	Insufficient contrast or wrong white support.	Add white background/quiet zone and validate after printing.