Mesh in one paragraph
A mesh number counts the openings per linear inch of a test sieve. A 325-mesh sieve has openings of about 45 µm, so "325 mesh talc" means most of the powder passes that sieve. Each step up in mesh is a smaller opening and a finer powder.
| Mesh | Opening (µm) |
|---|---|
| 200 | 75 |
| 230 | 63 |
| 270 | 53 |
| 325 | 45 |
| 400 | 38 |
| 500 | 25 |
| 635 | 20 |
Sieves stop being practical at around 500–635 mesh. Finer talc grades are described by laser particle-size results instead. Plant capacities quoted in mesh beyond that — company records give 250 to 2,500 mesh for SKZ's Peshawar plants — should be read as equivalent fineness, and confirmed with a D50/D97 figure on the order.
D50, D97 and why the median is not enough
Laser diffraction analysers such as the Bettersizer ST used by SKZ Laboratory Peshawar measure the whole particle-size distribution. D50 is the size at which half the particles, by volume, are smaller. D97 (or D98) is the size below which nearly all particles fall. It is the "top cut", and it matters for grit in films and coatings.
Two powders can share a D50 and still behave differently if one has a long coarse tail. Ask for both numbers when fineness is critical.
Sieve residue
Sieve residue is the small share of material retained on the test sieve. The two SKZ lab reports on this site both show 0.03 for above-325 and above-400 mesh samples. For coatings, films and thin-walled plastics, low residue means fewer visible specks.
Choosing a fineness
- Ceramics and rubber: often coarser grades, around 200–325 mesh
- Paints and paper: commonly 325 mesh and finer
- Plastics reinforcement: fine to micronized grades, specified by D50
- Cosmetic and pharmaceutical users: micronized grades, qualified by the buyer's own testing
These are common starting points, not rules. Your formulation and process decide. Send your current specification or a sample of the talc you use today, and it can be matched against what the plants produce.