Most matting projects in waterborne clear wood systems start with a gloss number. The customer wants 25 GU, or 40 GU, and the obvious question is which grade reaches that target at the lowest loading.
That framing produces a poor first screening round, because reaching the gloss target is rarely the hard part. Almost any silica of the right particle size will pull gloss down. What separates a usable grade from an unusable one is what happens to the film while gloss drops: whether the coating stays clear, whether the grain stays legible, and whether the surface still feels right under a hand.
Why clarity is the constraint
A matting agent works by creating microscopic roughness at the film surface, which scatters reflected light instead of returning it in one direction. The particles that create that roughness sit within a film that, in a clear wood topcoat, is typically 20–40 µm thick after cure.
Two things can go wrong. If particles are too large relative to film thickness, they protrude and scatter light inside the film as well as at the surface — the coating reads as hazy or milky, and the wood grain underneath greys out. If particles agglomerate rather than disperse, the same problem appears in patches rather than uniformly, which is worse because it looks like a defect rather than a finish.
On a pigmented system neither failure mode matters much: the film is already opaque. On a clear wood topcoat, where the entire point is that the substrate shows through, both are immediately visible and both are grounds for rejection.
Film build changes the answer
The same grade can behave differently in a 20 µm film and a 40 µm film. Thicker films tolerate larger particles because the particle sits proportionally deeper relative to the surface. Thinner films need finer routes.
This is why a grade that worked in one customer's system fails in another's with the same nominal gloss target. The gloss target was the same; the film build was not.
What particle size actually tells you
Particle size is the first number anyone looks at, and it is a useful starting point. But it is one input among several, and treating it as the whole picture leads to two specific mistakes.
Mistake one: assuming finer is always better for clarity. Finer particles do reduce haze, but they also reduce matting efficiency — you need more of them to reach the same gloss, and higher loading brings its own problems with viscosity and film integrity. There is a point where a finer grade at high loading produces a worse film than a slightly coarser grade at moderate loading.
Mistake two: comparing grades at matched loading rather than matched gloss. If you run two grades at 3% each and one lands at 30 GU while the other lands at 45 GU, you have not compared their clarity. You have compared one grade at target against another grade that has not reached target yet. Adjust loading until both hit the same gloss, then compare haze, grain definition and feel. That is the comparison that means something.
Structure and surface treatment
Beyond size, two properties change how a grade behaves in a waterborne system:
- Pore structure affects how much binder the particle absorbs during film formation, which influences both matting efficiency and how the surface feels once cured.
- Surface treatment — typically a wax after-treatment — changes dispersibility, settling behaviour and scratch resistance. Untreated grades disperse differently and tend to give a different tactile result.
These are not visible in a particle size figure, which is why two grades with the same nominal range can produce noticeably different films.
Structuring the first screening round
The most common way a first round is wasted is running a single grade and adjusting loading until the gloss target is met. That answers whether one grade can reach the target. It does not tell you whether a different route would reach the same target with better clarity, better feel, or at lower cost.
A more useful structure is two grades from different routes, both adjusted to the same gloss target:
- A lead grade — the route most likely to work based on your resin system, film build and gloss target.
- A comparison grade — typically finer, to establish whether the extra clarity is worth the additional loading, or coarser, if the lead grade is struggling to reach target.
Both run against your own current product as a control. Without a control, "acceptable clarity" is a judgement call; with one, it is a comparison.
What to measure
Five dimensions decide whether a grade progresses past the first round. Test them in this order — the first two are pass/fail, the rest are trade-offs.
| Dimension | What to look for |
|---|---|
| Gloss | Lands in the target window at a reasonable loading. Measure at your standard geometry — 60° and 85° readings tell different stories on a matte surface. |
| Clarity and haze | Over a dark substrate, look for milkiness or whitening. Grain should stay legible and the film should retain depth rather than reading flat. |
| Surface feel | Run a hand across the panel. Drag, chalkiness or a coarse texture at target gloss usually points toward a finer route. |
| Viscosity and dispersion | How long to disperse, how much viscosity rises, whether the process window stays open at production shear rates. |
| Storage stability | After accelerated storage, does material settle into a soft sediment that stirs back in, or hard-pack? Soft settling is workable; hard packing is not. |
A note on gloss measurement
On low-gloss surfaces, the geometry you measure at matters more than it does at high gloss. A 60° reading and an 85° reading on the same panel can suggest different conclusions, and two labs comparing results at different geometries will disagree about whether a grade hit target. Agree the geometry before the samples ship.
When to change route
Three signals suggest the lead grade is wrong rather than the loading:
- Haze appears before the gloss target is reached. The particle size is too large for the film build. Go finer.
- Loading is very high but gloss barely moves. Either the grade has low matting efficiency for this system, or dispersion is incomplete — check dispersion before assuming it is the grade.
- Appearance is patchy rather than uniformly hazy. This is usually dispersion or wetting, not particle size. Changing grade will not fix it.
The third case is worth dwelling on, because it is frequently misdiagnosed. A grade gets rejected for producing a mottled surface when the actual problem was dispersion energy or a wetting additive. The next grade produces the same result, and the conclusion becomes "silica matting does not work in this system." Check dispersion first.
Where Vistamatt grades fit
Our waterborne clear wood route is organised around this constraint. The lead grade for most systems is Vista-660 (5.0–5.3 µm), which balances matting efficiency against clarity in typical clear topcoat film builds. Vista-651 (4.9–5.2 µm) is the finer comparison route where smoothness and tactile quality lead the brief. Vista-351C serves as a bridge grade for customers moving from a general-purpose matte system.
Which of these should lead depends on your resin, film build and gloss target — that is the conversation we would rather have before samples ship than after they fail.
Screening starts with the system
Resin, target gloss, film build, current problem. We reply with a plan.