Mesh size is the single specification that most often decides whether a mineral filler works or fails in your process. This guide explains what mesh actually means, how mesh relates to D50 and D97, and how to pick the right grade for plastics, coatings, paper, rubber and construction.
Mesh is a screening convention, not a particle measurement. A "325 mesh" powder has passed through a screen with 325 openings per inch, which corresponds to roughly 44 µm. Because screens are made of woven wire, the practical floor for screening is around 400 mesh (about 37 µm). Anything described as 600, 1250 or 3000 mesh was not actually sieved — it was classified in an air classifier, and the mesh figure is an industry shorthand for fineness.
That is why mesh alone is a poor purchasing specification. Two suppliers can both quote "1250 mesh" and deliver powders that behave completely differently, because mesh says nothing about the shape of the distribution.
Mesh to micron: the conversion you actually need
| Mesh | Approx. opening | Typical use |
|---|---|---|
| 200 | 74 µm | Construction filler, desulphurisation, bulk plastic filling |
| 325 | 44 µm | General industrial filler — paint, rubber, ceramic, mortar |
| 400 | 37 µm | Plastic modification, general coatings |
| 600 | 23 µm | Masterbatch, fine coatings, paper filling |
| 800 | 18 µm | High-gloss plastics, coatings, premium paper |
| 1250 | 10 µm | High-gloss and transparent plastics, fine inks |
| 1500 | 8 µm | High-end coatings, cosmetic auxiliaries |
| 2500 | 5 µm | Nano coatings, optical plastics, cosmetics |
| 3000 | 4 µm | Ultra-fine functional filler, EVA foaming |
D50 and D97 are the numbers that predict performance
D50 is the median particle size — half the particles are smaller. It controls surface area, oil absorption and how much filler you can load before the melt viscosity becomes unworkable. D97 is the size below which 97% of particles fall; it governs the coarsest particles in the powder, and those coarse particles are what cause surface defects, film roughness and pinholes in thin coatings.
As a rule of thumb, a well-classified powder has D97 no more than about 3× its D50. A wide, uncontrolled distribution with an oversized tail is the most common cause of "the filler ruined my surface finish".
Choosing by application
- Plastics and masterbatch: 800–3000 mesh depending on the required stiffness and gloss. Higher mesh increases impact strength retention and surface gloss but reduces the maximum loading.
- Architectural and industrial coatings: 800–1500 mesh for opacity and film smoothness; 325–600 mesh where film build and cost dominate.
- Papermaking: 600–1500 mesh for filling, 1500–2500 mesh for coating colour, where brightness and printability matter more than loading.
- Rubber: 325–800 mesh; the layered structure of talc also aids processing and release.
- Construction and mortar: 200–400 mesh for bulk filling; 10–80 mesh when a decorative aggregate is wanted rather than a filler.
What to put in your enquiry
Rather than "please quote 1250 mesh talc", send us: the application, the target D50 and D97, the required whiteness and SiO₂ or CaCO₃ content, the loading level in your formulation, and the packaging format. We will come back with the grade that fits, a TDS for bench testing, and a free sample.
If you are still narrowing it down, our technical team can compare two or three grades against your formulation — most projects settle after one round of samples.
Written by the technical team at TDHX Minerals, Haicheng, Liaoning, China.
