Varnish in UV printing: gloss, protection and effects

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Varnish, often called gloss or clear coat in UV printing, is ink without pigment. It is printed and cured like any other colour, but stays transparent. With it you can make surfaces shine, highlight parts of a design and protect the print from abrasion.

What varnish is and how it is printed

Many UV printers have a dedicated channel for varnish, alongside CMYK and white. It is usually printed as the last layer over the colour. Because it comes from the print head, it can be placed just as precisely as colour: over the full area, only on individual elements or in several layers on top of each other.

Not every machine has a varnish channel. Some desktop machines use the channel for either varnish or primer, others have none at all. Check this in your machine’s data sheet.

Gloss varnish

A full-area layer of varnish makes the print glossier and the colours look richer. For photos on metal or wood, this is often the difference between “printed” and “finished product”.

How strong the gloss becomes depends on how smoothly the varnish flows before it cures. Many machines offer a dedicated mode for this: the lamp cures a little later, the varnish can level out and becomes glossier.

Spot varnish

With spot varnish, only part of the design gets varnish. Typical examples are a logo, a lettering or individual details such as water droplets. The contrast between the matt surface and the glossy element creates the effect. It is well known from high-quality business cards and packaging.

With several layers of varnish on top of each other, a tangible relief is created. This can imitate embossing, braille or textures such as leather or brush strokes. More on this in Relief and texture.

Matt instead of glossy

A matt look is also possible. For this, the varnish is cured immediately after it lands, before it can flow. The tiny droplets remain as a rough structure and scatter the light. Some machines have a dedicated matt mode for this, with others the effect results from the lamp setting.

One note: how matt or glossy the result is depends heavily on the machine, the lamp and the substrate. A test print is unavoidable.

Protective function

Varnish protects the colour layer beneath it. Scratches end up in the varnish first, not in the colour. This is particularly useful for:

• key rings, phone cases and other things that are handled a lot
• metal and photo prints that get cleaned
• outdoor products, although varnish does not guarantee the UV resistance of the colours

Varnish does not make a print indestructible, though. If adhesion to the material is poor, everything flakes off together, varnish included. The foundation remains the right preparation with primer.

Cost and time

Varnish is not free:

• Ink: Clear varnish costs about as much as coloured ink. Over a full area on large plates, that adds up.
• Print time: Every layer of varnish is another pass. A glossy varnish with delayed curing often takes even longer. With relief in many layers, the print time can multiply.
• Maintenance: An additional channel means additional nozzles that have to be looked after.

So factor the varnish into your calculation instead of seeing it as a free extra. More on this in the UV costing.

Setting up varnish in the file

For the print software to know where varnish should go, you need a separate layer or spot colour. The principle is the same in most programs:

1. Set up the design normally in CMYK.
2. Create the area that should get varnish as a separate element, for example as a copy of the logo.
3. Fill this element with a spot colour named the way your RIP or print software expects.
4. Set the layer to “overprint” so that the colour beneath is not knocked out.

With greyscale it depends on the software: usually a dark spot gets more varnish, while some programs do it the other way round. A test print shows how it works for you. This is how domes and gradients can be created in relief. What the spot colour must be called and how to separate white and varnish cleanly is explained in Preparing print data.

For business use

Spot varnish is one of the simplest ways to make a product look more high-quality. For customers the difference is immediately visible and tangible. Offer it as a paid option. For products that are handled a lot, full-area protective varnish as standard is worthwhile, because it reduces complaints about scratches.

Continue with: Preparing print data and Relief and texture.

Bubbles, dots or craters in the varnish? Causes and solutions are in Bubbles and craters in varnish.