Ink is the part of a UV printing job that customers ask least about and that decides most. The same file printed with a different layer construction on the same substrate can look identical on the bench and behave differently in service, and the difference is decided before the machine starts.

This guide covers how the ink choice is made in practice: why it follows the substrate, what the published configurations include, what a rigid construction suits, when flexibility matters, how white and varnish change the stack, how a new material is tested, and what the record should contain.

Why does the ink choice follow the substrate?

Because adhesion starts at the surface.

The published position is that the substrate, coating and preparation decide whether the ink bonds, so the ink is chosen for the material rather than for the artwork.

The published material guidance for this range is consistent on this point across every substrate it covers. Metal, glass, wood, acrylic, stone and containers are each treated as a qualification exercise, and each begins with identifying the material, the coating and the batch rather than with selecting an ink. That order is deliberate, because a surface that has not been identified cannot be matched.

The practical consequence is that ink selection is a late decision rather than an early one. The artwork is drawn, the material is identified, the preparation is fixed, and the layer construction follows from those inputs. A shop that starts from the ink is working backwards.

What does the published ink configuration include?

Colour, white and varnish channels.

The published configurations across this range run from CMYK plus white plus varnish to extended eight-colour sets that add light cyan and light magenta.

The number of channels matters in two different ways. More colours extend the range that can be reproduced smoothly, which is what light cyan and light magenta contribute. More layers extend what can be built at all, which is what white and varnish contribute. A job that needs a white underbase and a spot varnish needs channels for both, and no amount of colour range substitutes for a missing layer.

What does a rigid construction suit?

Flat and stiff parts that will not flex.

A rigid part such as a panel, a sign or a nameplate does not bend in service, so the ink film is not asked to move with the material.

That makes the rigid case the simpler one, and it covers most of the applications in this range: signage, decorative panels, nameplates, tiles and fixed display work. The published guidance for these substrates concentrates on surface preparation, white coverage and the durability the part will meet, because the film itself is not under mechanical stress.

The complication on rigid work is usually the installation rather than the service. A panel that is routered, drilled, bent or fastened after printing puts mechanical demand on the print at the point of the operation, which is why the published guidance asks for cut paths, clearances and no-print zones to be defined before the artwork is approved.

There is a second practical point about rigid work: the ink is not the only thing that decides how the finished part behaves. Preparation, the white layer and the curing condition all contribute, and a change in any one of them can move the result. That is why the published approach is to qualify the whole construction on a representative part, rather than to treat the ink selection as the answer on its own.

When does a flexible construction matter?

When the printed material moves.

A part that flexes, bends or is handled heavily asks the film to move, and the published approach is to test the real handling cycle on the real material.

Flexibility is not a property of the ink in isolation; it is a property of the film on a substrate under a particular movement. A cured layer that tolerates a slight bend on a rigid panel may behave differently on a thin sheet that is rolled, and differently again on a part that is flexed repeatedly by hand.

That is why the published approach for this range is to test the finished part rather than to select from a list. The published material guidance repeats the same instruction for every substrate: test the actual material and the actual handling, and keep the approved sample with the record so a repeat order inherits the qualification.

How does white change the construction?

It is a layer, not a background.

The published artwork guidance asks for white to be supplied as its own channel, so opacity can be placed deliberately instead of being applied everywhere.

White does different jobs on different materials, and the published substrate guidance reflects that. On a clear panel it defines where the image is opaque. On a dark or coloured surface it decides whether the colour reads at all. On a reverse-printed transparent part it changes the order of the layers entirely, because the image is viewed through the material.

The published artwork guidance for this range asks for white underbase and varnish areas to be defined as separate data rather than as part of the colour image, so that full, selective and spot effects can be controlled independently. On a mixed job that separation is what allows one area to be opaque and another to transmit, which is not possible when everything arrives flattened.

What does varnish add?

A controlled finish and a protected surface.

The same channel can produce an overall gloss, a spot highlight or a raised effect, and the published guidance is to validate it on the real material.

Varnish is often chosen for appearance and then justified for protection, and the order should be reversed. On a handled part the varnish is part of the surface the user touches, which means it should be selected against the handling requirement and then checked for the look it produces rather than the other way round.

The published guidance for this range treats the varnish channel as part of the same layer decision as white, which is why the two are described together in the artwork guidance. Both are layers that can be placed, and both should be approved on the finished part rather than on a proof.

How should a new material and ink be tested?

On the real part, through the real process.

The published rule for this range is that a listed material is not automatically production-ready, so the test uses a representative part rather than a coupon.

The published test sequence asks for more than appearance. Colour, adhesion, scratch resistance, white-underbase coverage and any varnish effect are all checked on a representative sample, and the published guidance is to take that sample through the same handling and finishing sequence planned for production.

Two published methods support the result. Adhesion is assessed with the cross-cut tape method under ASTM D3359 and wear under ASTM D4060. Where the material is handled or cleaned, the corresponding exposure belongs in the same test rather than in a later conversation.

What should the record contain?

The ink, the layers, the substrate and the result.

The published process record covers the artwork version, the settings, the substrate and pretreatment and the inspection result, which is the set that makes a repeat job reproducible.

Three fields are specific to the ink decision. The ink family or batch, so a supplier change is visible. The layer construction, so the white and varnish placement is recoverable. And the preparation method, because on several substrates the preparation is what makes the ink work at all.

The published approach is to keep that record with the approved sample, so a later order is checked against the same physical piece. The chemical and material obligations for the inks follow the applicable regulations (REACH), occupational guidance for the workshop is published by the relevant authority (HSE printing), and colour and process practice is published by the bodies in the field (International Color Consortium, PRINTING United Alliance). Cost per square metre is covered separately in the guide to UV ink cost, and the layer requirements for the file are set out in the article on preparing artwork files.

What the decision comes down to

Ink is a late decision made from three inputs: the material, the handling and the appearance. Identify the surface, decide whether the film has to move, place the white and varnish layers deliberately, and test the construction on the real part before the job is released.

The published configuration and layer guidance for this range sits with the AJ2130EX and AJ360i pages, the cost side is covered in the guide to UV ink cost per square metre, and the layer requirements are set out in the article on preparing artwork files.