01How spot UV works
UV coatings are liquids that cure into a hard, clear film the moment ultraviolet light hits them. Duplo, a maker of finishing equipment, describes the cure as instant, hardening the coating for immediate handling. Coating the whole sheet is flood UV. Coating only some areas, through a mask, is spot UV.
The effect is contrast. A glossy logo on a matte box catches light when the box turns; on a gloss background there is little contrast. That is why spot UV is usually paired with matte or soft-touch lamination, and why one German finisher's spec says it works best on a single-color dark background.
02How it is applied
| Method | How | Register | Notes |
|---|---|---|---|
| Offset UV varnish | In line on the press or in a second run | Matches the offset print closely | Fine detail; can run over folds and into the bleed |
| Screen-printed spot varnish | Off line, after printing | Minor shifts are unavoidable | Minimum line width 0.5 mm at this finisher; needs a laminate over metallic inks |
Raised (3D or dimensional) spot UV builds the coating up so the glossy area stands up to the touch. Digital inkjet coaters do it without dies or screens; Duplo's DDC-810 Pro, for example, lays down 15 to 80 microns. Not every printer offers it; ask how they make it and for a sample at the thickness being quoted.
03How to set up a spot UV file
- Duplicate the artwork and keep only the areas to be coated.
- Fill those areas with solid 100% black (K). No gradients, tints or gray.
- Supply it as a separate layer or a separate file, aligned exactly to the artwork and the dieline.
- Ask the printer before running spot areas across folds and creases.
- Leave small gaps around tight edges if the printer's register tolerance is loose.
Printers differ: 4over4 asks for solid 100% K, Duplo describes defining the areas in black, and Topac takes the areas as vector or halftone elements in the artwork. Use the instructions your printer sends.
04Where spot UV fails
- Uncoated and porous stock: on uncoated or porous materials the gloss level drops and the varnish tends to crack, according to Topac's screen varnish spec. Uncoated kraft is in this group, so ask for a sample.
- Metallic inks: screen-printed spot varnish does not adhere to metallic inks without a laminate under it (Topac).
- Foil on top: matte UV finishes are not a suitable base for hot foil stamping, and a foil stamp cannot go on top of UV matte varnish (Topac).
- Tiny type and hairlines: Tradeprint advises against them because its spot UV can land about 0.5 mm off, and Topac sets a 0.5 mm minimum line width for screen varnish.
- Recyclable claims: the Paperboard Packaging Council tells converters not to print its recyclable logo on UV-printed boxes, so check any "recyclable" claim with the printer before adding UV.
05Spot UV vs other finishes
| Finish | What you see and feel | Pairs with spot UV? |
|---|---|---|
| Gloss lamination | Shiny film over the whole surface | Little contrast between gloss and gloss |
| Matte or soft-touch lamination | Flat, velvety surface | Yes, the classic pairing |
| Embossing or debossing | Raised or pressed-in shape | Ask the printer about combining them and in which order |
| Foil stamping | Metallic or colored foil | Check order and base with the printer |
For raised shapes without coating, see embossing vs debossing. Spot UV is used on folding cartons and the wrap of rigid boxes. If you are quoting finishes with an overseas factory, The Vault in the Product Sourcing Secrets course lists packaging factories with contacts.
06How to spec it with a supplier
Spot UV is one line on a packaging quote. Make it specific so every printer quotes the same thing.
| No. | Field | What to write |
|---|---|---|
| 01 | Finish | Spot UV gloss, flat or raised, and the thickness if raised |
| 02 | Base | The lamination or coating under it: matte, soft-touch or none |
| 03 | Areas | Which panels, and the mask file name |
| 04 | File | Separate layer or file, solid 100% K, aligned to artwork and dieline |
| 05 | Board | Coated paperboard or the wrap paper name and GSM |
Questions to ask the supplier
- Do you apply spot UV on press, by screen or digitally, and what register tolerance should we design for?
- What is your minimum line width for the spot areas?
- Can you send a printed sample of spot UV over this exact lamination?
07FAQ
Q01What is spot UV?
A clear, glossy coating applied only to selected areas of a print and cured instantly with UV light, usually over a matte background so those areas shine.
Q02Is spot UV raised?
Raised or 3D spot UV is: it builds the coating up so the area stands up to the touch (Duplo's digital coater lays down 15 to 80 microns). Ask your printer which kind it is quoting.
Q03How do I set up a file for spot UV?
Make a separate layer or file with the coated areas in solid 100% black and nothing else, aligned to your artwork. Follow your printer's own instructions.
Q04Can spot UV go on kraft or uncoated paper?
Test it first. Topac warns that on uncoated or porous stock the gloss drops and its screen-printed varnish tends to crack. Coated board or a laminated surface is the safer base.
Q05What is the difference between spot UV and gloss lamination?
Gloss lamination is a film over the whole surface. Spot UV is a coating on chosen areas, used for contrast against a matte surface.