White Ink Underprint on Clear, Metallic and Kraft Pouches: How It Works and How to Set Up Artwork
Quick answer
Process inks are transparent, so on clear, metallised or kraft film they take on the colour of the material underneath. A layer of opaque white printed behind the colours makes them look as they do on white paper. In the artwork, build the white as its own spot colour named clearly (for example "White"), on a separate layer set to overprint; leave it out wherever you want the metallic or clear film to show, choke (shrink) it slightly, commonly 0.15 to 0.25 mm, so it does not peek out at edges, and always put solid white under barcodes and small text. Approve the result on the real film, not on screen.
Quick facts: Cannabis Mylar Bags
- Indicative unit price: about US$0.05–0.10 per piece. This is a guide, not a quotation: the final price depends on size, material, print colours, finish and order quantity.
- MOQ: typically from 500 pcs per size and artwork; the confirmed minimum depends on material, print method and features and is stated on the quotation.
- Lead time: Physical samples 5–7 working days after artwork is confirmed; bulk production 20–30 days after sample approval.
- Who makes it: BestPackFactory’s own factory in Longhua District, Shenzhen, China. Free dieline and artwork proof within 24 hours. See real samples and videos.
- Specifications and quote: Cannabis Mylar Bags · Request a quote
On white paper, the paper itself is the white. On a clear, metallised or kraft pouch there is no white unless it is printed. That single fact explains most surprises buyers see on their first flexible packaging proof: colours that look dark or dull on kraft, a logo that turns silver on a metallised bag, or text that disappears on a clear window. This guide explains how white underprint works and how to prepare the file. For choosing between digital and gravure printing for pouches, see our digital vs rotogravure guide.
How white underprint works
CMYK and most spot inks are transparent. Printed directly on a coloured or reflective material, they act like a coloured filter:
- On clear film, colours look weak and see-through, and anything coloured white in your design file is simply not printed, so it becomes transparent.
- On metallised film or foil, colours take on a metallic sheen, and white areas in the design show as bare silver.
- On brown kraft, colours shift darker and warmer, and light colours and pastels nearly disappear.
A white ink layer printed under the colours gives them a neutral background. In many laminated pouches the outer film is reverse printed, meaning the inks are printed on the inside face of the film and then laminated: the colours are printed first and the white goes behind them. On surface-printed materials such as kraft paper the white is printed first. Either way, the artwork setup is the same; the printer handles the order.
Where to put white by substrate
| Substrate | White under colours | Leave white out to… | Watch for |
|---|---|---|---|
| Clear film (window pouches) | Under all artwork that should look solid | Create see-through windows | Text over the window needs its own white or it becomes hard to read |
| Metallised film or foil laminate | Under colours that should look flat and bright | Create metallic colour effects (colour printed on bare metal) | Barcodes and fine text must sit on solid white |
| Brown kraft paper | Under colours that must look clean and bright | Keep the natural kraft look | White on kraft is rarely fully opaque; some brown shows through |
| White film or white kraft | Usually not needed | Not applicable | Confirm whether the supplier still recommends a white layer |
Artwork setup checklist
- Create a named spot colour for white. Use one clear name such as "White" or the name your supplier asks for, so prepress can find it. Never use the default white swatch (0/0/0/0), because that means no ink.
- Put it on its own layer. Place the white shapes on a separate layer called "White" above or below the artwork, and do not mix it into the colour layers.
- Set the white to overprint. Mark the white objects as overprint so they do not knock out the colours on screen or in the PDF. Display it in a visible tint in your file and tell the supplier it represents opaque white ink.
- Knock out where you want the material to show. Delete or cut out the white where the metallic or clear film should show through. Metallic-effect logos are made by printing colour over areas with no white.
- Choke the white slightly. Shrink the white shape inside the edges of the colour above it, commonly by about 0.15 to 0.25 mm, so small registration movement does not leave a white halo. The exact value depends on the press and is confirmed on the proof.
- Use solid white under barcodes and small text. Barcodes need a solid white patch that also covers their quiet zones; see our pouch barcode placement guide. Fine text and thin lines also need full white or they become hard to read.
- Ask about double white on kraft or clear. A second white hit can increase opacity where colours must look bright. Whether it is available and how it affects cost is confirmed in the quotation.
- Keep the white within the printable area. Stop the white away from seals, the zipper and the tear notch according to the supplier's stand-up pouch dieline.
Decision rules
- Use full white underprint when brand colours must match a reference closely on a non-white material.
- Use selective white when you want a mix of metallic or clear effects and solid colours on the same bag, as is common on cannabis mylar bags and premium snack pouches.
- Use no white on kraft when a natural, darker printed look is the intent, and choose dark colours that work on brown.
- Choose white film instead of clear or metallised film when you need a white background everywhere but no metallic or window effect.
Proofing on real film
A screen or paper proof cannot show what white ink does on clear, metallised or kraft materials. Ask for a printed sample or press proof on the actual film or laminate. Check colour against your reference with and without the white, look at edges for white halos, and view metallic areas under good light. The approval should record the material, whether white is single or double, and the agreed colour reference. Our packaging colour management guide covers colour references.
What to send in your RFQ
- Pouch type, size and material: clear, metallised, foil laminate or kraft.
- Artwork with the white as a named spot colour on its own layer, set to overprint.
- A note of where metallic or clear effects are intended.
- Barcode position and size.
- Colour references for critical brand colours.
- A request for a proof or sample on the real material.
Common mistakes
- Using the default white swatch for logos on clear or metallised film, so the logo prints as nothing.
- Forgetting to set the white to overprint, which knocks out the colours in the PDF.
- Putting a barcode directly on metallised film without a white patch.
- Expecting white on brown kraft to look as bright as white paper.
- Approving colours from a screen proof of a clear or metallic bag.
Related products: custom stand-up pouches.
Frequently asked questions
Why do I need white ink on a clear or metallic pouch?
Most printing inks are transparent. Without a white layer behind them, colours look weak on clear film, metallic on metallised film and dark on kraft. White underprint gives them a neutral background.
How do I set up white ink in my artwork?
Create a named spot colour such as White on its own layer, set it to overprint, remove it where you want the film to show, choke it slightly and use solid white under barcodes and small text.
What choke should I use for the white layer?
A common range is about 0.15 to 0.25 mm inside the colour edges, depending on the press. Confirm the value with the supplier and check it on the proof.
Is white ink opaque on kraft paper?
Usually not fully. Some brown typically shows through a single white layer. Ask whether a double white hit is available and approve the result on a printed sample.
Related pages
Prepare a quote-ready packaging brief
Send the pouch type, size and material, artwork with the white layer set up as a named overprint spot colour, a note of metallic or clear effects, colour references and a request for a proof on the real film. Every BestPackFactory product is made in our own factory, and custom packaging is quoted as a B2B project with a site-wide MOQ of 500 PCS. Reach Lisa Wu at lisa@colorprintingpackage.com or WhatsApp +86 158 8653 0985; anything not listed here is confirmed in the quotation.
Request a project quote