Calcium Carbonate Knowledge Hub
What Is 400 Mesh Calcium Carbonate?
2026-09-04 16:37:43
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400 mesh calcium carbonate is a fine ground calcium carbonate (GCC) grade in which the powder is specified to pass through a No. 400 sieve. Under ASTM E11 sieve conventions, a No. 400 sieve has a nominal opening of 38 µm, or 0.038 mm.
It is finer than 200 mesh and 325 mesh calcium carbonate and is commonly used where a smoother filler, lower coarse residue, and more uniform texture are needed—such as wall putty, rubber, artificial stone, floor tiles, selected plastics, sealants, paints, and construction chemicals. However, “400 mesh” is a sieve reference, not a complete technical specification. The buyer should also define the required passing percentage, chemical purity, whiteness, moisture, and application performance.
What Does 400 Mesh Mean?
Mesh describes the number of sieve openings per linear inch. As the mesh number rises, the opening becomes smaller. A No. 400 sieve has 400 openings per inch and a nominal aperture of 38 µm.
| Term | Value | Meaning |
|---|---|---|
| 400 mesh | No. 400 test sieve | A sieve with 400 openings per linear inch |
| Nominal opening | 38 µm | Equivalent to 0.038 mm or about 0.0015 inch |
| Passing percentage | Agreed buyer–supplier requirement | Defines how much material passes through the No. 400 sieve |
| Residue | Material retained on the sieve | Controls oversized particles and grit |
A 400 mesh powder is not made up of identical 38 µm particles. It contains a particle-size distribution, usually including many particles much smaller than 38 µm. Because particles are irregularly shaped and can form soft agglomerates, sieve analysis should follow an agreed method and sampling procedure.
400 Mesh vs Other Grades
| Grade reference | Nominal sieve opening | Relative fineness | Typical use direction |
|---|---|---|---|
| 200 mesh | 75 µm | Coarse powder | Mortar, asphalt, agriculture, general construction filler |
| 325 mesh | 44–45 µm | Fine powder | Putty, mortar, rubber, sealants, selected coatings and plastics |
| 400 mesh | 38 µm | Finer powder | Rubber, artificial marble, floor tiles, putty, selected plastics, construction chemicals |
| 500 mesh | 25 µm | Very fine sieve grade | Finer fillers and applications needing lower coarse residue |
| Low-micron GCC | Defined by D50 and D97 | Ultrafine | Premium PVC, masterbatch, coatings, paper, sealants, and specialty products |
400 mesh remains a sieve-defined powder grade. At finer levels, the industry increasingly uses laser particle-size measurements such as D50 and D97, because fine powders can agglomerate and routine sieving becomes less reliable for showing the complete particle-size distribution.
How 400 Mesh Calcium Carbonate Is Produced
400 mesh calcium carbonate is usually made by dry processing calcite-rich limestone, marble, chalk, or calcite ore. The material is crushed, dried when necessary, ground, and screened or air-classified to limit oversize particles.
Selected carbonate feed → crushing → moisture control → fine grinding → No. 400 screening or air classification → powder collection → quality testing → bagging, FIBC, or bulk loading
The raw material strongly affects final product quality. High CaCO3, low silica, controlled MgO, low iron, and stable whiteness are important for applications such as white wall putty, artificial stone, rubber, light-colored plastics, and floor tiles. Hard impurities such as quartz, chert, and flint can increase mill wear and leave abrasive grit in the final powder.
Production controls
Stable mill feed: Consistent crushed feed size supports steady grinding and product fineness.
Low moisture: Wet powder can reduce mill capacity, blind screens, create agglomerates, and cake during storage.
Air classification: Often used to remove coarse particles and control residue more efficiently than screening alone.
Dust collection: Captures fine powder, improves product recovery, and maintains clean plant conditions.
Contamination control: Magnets and clean handling reduce tramp iron and dark-speck risk.
Batch testing: Passing percentage, residue, moisture, chemistry, whiteness, and bulk density should be verified.
Common Applications
400 mesh calcium carbonate is generally used as a fine mineral filler. The correct grade for each application depends on more than mesh: surface treatment, purity, moisture, color, and particle-size distribution can all influence results.
| Application | Role of 400 mesh calcium carbonate | Key product controls |
|---|---|---|
| Wall putty and skim coat | Fine filler that supports smoothness, coverage, and formulation economy | Whiteness, particle size, moisture, flowability, and batch consistency |
| Rubber products | Cost-effective filler that can adjust hardness, volume, and processing behavior | Purity, fineness, moisture, dispersion, and compatibility with the rubber compound |
| Artificial marble and engineered stone | Mineral filler that contributes to color, particle packing, and cost control | Whiteness, controlled residue, low moisture, and compatibility with resin systems |
| Floor tiles and ceramic-related products | Filler used in selected formulations to support color and material cost control | Whiteness, CaCO3, low impurities, fineness, and formulation testing |
| Sealants and adhesives | Fine filler for rheology, density, extrusion behavior, and formulation economy | Particle size, moisture, oil absorption, surface treatment, and low grit |
| Selected plastics and PVC compounds | Mineral filler where a medium-fine powder is acceptable | Whiteness, PSD, low moisture, coating condition, and compound performance |
| Paint and construction coatings | Extender filler in selected systems | Whiteness, low grit, dispersion, oil absorption, and viscosity response |
Industry application guidance identifies 400 mesh GCC as a common rubber filler and describes its use in floor tiles, artificial marble, coatings, plastics, and construction-related products.
400 Mesh for Rubber and Plastics
In rubber, 400 mesh calcium carbonate can provide economical volume filling and may influence hardness, processing behavior, and compound cost. The actual effect depends on the rubber type, filler loading, cure system, other fillers, and mixing process. A finer or coated calcium carbonate may be needed when better dispersion or more controlled mechanical performance is required.
In plastics and PVC, 400 mesh material may be appropriate for some cost-sensitive applications, but it is usually coarser than the grades used for high-surface-quality products. For white PVC profile, cable compounds, thin film, high-filler masterbatch, or high-gloss products, buyers often require finer GCC with tighter D50, D97, moisture, and surface-treatment specifications.
If the material is intended for PE, PP, PVC, rubber, sealants, or adhesives, confirm whether it is uncoated or stearic-acid-coated. A surface coating can improve compatibility with hydrophobic polymer matrices, but it does not replace particle-size control or improve low-quality raw material.
How to Specify a 400 Mesh Grade
“400 mesh calcium carbonate” should be a starting point for a technical specification, not the full specification. The following items help avoid disputes and ensure the powder fits the target process.
| Specification item | Why it matters |
|---|---|
| Passing percentage at No. 400 sieve | Defines the amount of powder finer than the 38 µm opening |
| Maximum No. 400 sieve residue | Controls coarse particles and grit |
| Test method and sample preparation | Ensures comparable results, especially for fine or agglomerated powder |
| CaCO3, CaO, and MgO | Confirms chemical purity and high-calcium or dolomitic character |
| SiO2, Fe2O3, and acid-insoluble residue | Controls abrasive impurities, color, and product cleanliness |
| Whiteness and brightness | Important for white putty, artificial stone, PVC, coatings, and tiles |
| Moisture | Controls powder flow, storage stability, packaging, and polymer processing |
| Bulk density | Important for formulation dosing, packing weight, and silo capacity |
| Coating condition | Confirms uncoated or treated GCC for polymer compatibility |
| Laser PSD, if needed | Adds D10, D50, and D97 data where the fine fraction affects performance |
Key Takeaway
400 mesh calcium carbonate is a fine GCC grade associated with a No. 400 sieve opening of 38 µm. It is used in applications such as wall putty, rubber, artificial marble, floor tiles, sealants, selected plastics, paints, and construction chemicals where a finer filler is needed than 200 or 325 mesh grades.
For reliable purchasing and production, define the required No. 400 passing percentage and residue, then confirm chemical purity, whiteness, moisture, bulk density, coating condition, and end-use performance. This is more useful than relying on “400 mesh” alone, especially where powder smoothness, dispersion, color, or low grit are important.
