Effect of gloss coating on matte canvas d-max

[Ryan Mack]

I don't fully understand how light scattering works with paper coatings. If you put a gloss coat on a matte canvas (printed with matte black ink) can you achieve the same d-max as you would by printing on a gloss paper? Or does the underlying matte canvas still cause light scattering that reduces contrast?

[Doug Gray]

I don't fully understand how light scattering works with paper coatings. If you put a gloss coat on a matte canvas (printed with matte black ink) can you achieve the same d-max as you would by printing on a gloss paper? Or does the underlying matte canvas still cause light scattering that reduces contrast?

The basic difference between MK and MPK inks is that the latter incorporates a gloss surface on the black pigments. This improves the DMax for glossy media but makes DMax worse for matte media. The reason it's worse for matte media is that matte texture is such that some light reflects off the gloss surface of the MPK ink. A similar worsening occurs when you coat matte media with a gloss coat.

[Mark D Segal]

What is "MPK"? I thought the ink choice is either MK or PK?

[Mark D Segal]

The reason it's worse for matte media is that matte texture is such that some light reflects off the gloss surface of the MPK ink. A similar worsening occurs when you coat matte media with a gloss coat.

What do you mean by this: that the gloss surface contributes to more scatter?

[Doug Gray]

What do you mean by this: that the gloss surface contributes to more scatter?

Yes, PK's glossy surface, just like window glass, reflects a portion of light hitting it. When it's on a glossy type surface, the surface, even with dimples such as semi-gloss or luster, doesn't deviate more than 15 degrees or so from flat. So reflected light from the PK surface does not extend to the angle where DMax is measured, which is at 45 degrees. Matte surfaces are rough by design and includes much larger angles. As a result, a portion of the PK ink gets positioned to reflect light by 45 degrees and this degrades the DMax. PK inks are really quite black and absorb nearly all light that isn't reflected from their encapsulated, glossy resin coat. This is why DMax is so much better on glossy media.

[Ryan Mack]

So what does applying a gloss varnish do to dmax on a matte canvas printed with matte black?

[Doug Gray]

So what does applying a gloss varnish do to dmax on a matte canvas printed with matte black?

Depends. For most true mattes it will make DMax worse. There are some media I've seen that are called semi-matte but they act more like luster and less like a true matte. Those might be unchanged or even get better.