How Many Microns Is Silica Sand? Micron, Mesh and AFS Conversion
How many microns is silica sand? How are grain sizes expressed in microns, mesh and AFS, and how do you convert between them? Conversion table and a size guide by application.
"How many microns is silica sand?" has no single answer, because silica sand is produced across a wide range, from fine micron-sized powder to coarse grains several millimetres across. What makes things even more confusing is that grain size is expressed in different units depending on the industry: microns (µm) in some places, mesh (sieve number) in others, and AFS in the foundry sector. In this article we explain these three systems and show you how to convert between them.
How Many Microns Is Silica Sand?
The grain size of silica sand depends on the application. Our product range, for example, spans from about 63 microns (0.063 mm) to 5 millimetres (5,000 microns). At the finest end, micronised products are powders in the micron range; at the coarsest end are grains several millimetres across. So the answer to "how many microns is silica sand" depends on which fraction you use. To determine the right size, you first need to know these units.
What Is a Micron (µm)?
The micron (micrometre, µm) is the most commonly used unit for measuring grain size. One micron is one millionth of a metre — one thousandth of a millimetre (1 mm = 1,000 µm). For comparison: a human hair is about 70 microns thick. Microns are preferred especially for fine materials and filler applications where precision is required, because they express the grain diameter directly.
What Is Mesh (Sieve Number)?
Mesh is the number of openings along one inch (2.54 cm) of a sieve. A 100 mesh sieve, for example, has 100 openings per inch. The important rule is this: as the mesh number increases, the opening gets smaller — meaning the grains get finer. In the USA, the US Sieve Series and Tyler standards are widely used, and they are based on the ASTM E11 standard.
A common convention in mesh notation is this: a "−" sign before a product means the grains pass through that sieve (finer), while a "+" sign means they are retained on it (coarser). For example, −100 +200 mesh means the grains pass through 100 mesh and are retained on 200 mesh — in other words, they fall within the range between the two. A single-number notation (e.g. 60 mesh) indicates an approximate average size, while a two-number notation (e.g. 30/70) indicates a range.
Micron–Mesh Conversion Table
The table below shows the approximate micron and millimetre equivalents of common mesh values (based on ASTM E11 / ISO 3310-1 nominal openings):
| Mesh | Micron (µm) | Millimetre (mm) |
|---|---|---|
| 8 | 2,360 | 2.36 |
| 10 | 2,000 | 2.00 |
| 20 | 850 | 0.85 |
| 30 | 600 | 0.60 |
| 40 | 425 | 0.425 |
| 50 | 300 | 0.30 |
| 70 | 212 | 0.212 |
| 100 | 150 | 0.150 |
| 140 | 106 | 0.106 |
| 200 | 75 | 0.075 |
| 325 | 45 | 0.045 |
As a practical shortcut you can use the relationship Mesh × Micron ≈ 15,000 (for example 200 mesh ≈ 75 µm), but for exact values the table above should be taken as the reference. These values are laboratory sieve openings; on production screens the actual opening may be slightly smaller depending on the wire thickness. A small practical detail: because 200 mesh corresponds to roughly 75 microns, micronised quartz products in Turkey are often referred to simply as "75 micron".
What Is AFS (Grain Fineness Number)?
In the foundry sector, grain fineness is usually expressed with the AFS (American Foundry Society) number. AFS is a weighted average fineness value calculated from the sand's sieve analysis; it is not the opening of a single sieve but the average of the entire grain size distribution. The rule is similar: the higher the AFS number, the finer the sand.
AFS is not exactly the same as mesh; it is calculated by multiplying the percentage retained on each sieve by the relevant factor and summing the results. Still, a rough correspondence can be drawn in practice: the 50–70 AFS range, for example, corresponds to a typical medium-fine foundry sand. You can see which AFS value corresponds to which grain size in our product fraction table.
Which Application Needs Which Size?
Different industries work with different units and different sizes:
- Foundry: fineness is expressed in AFS; typically 50–70 AFS. Foundry →
- Sandblasting: usually fractions in the 60–100 AFS range. Sandblasting →
- Water treatment / filtration: grain size is given in mm; typically 0.5–1.2 mm. Water treatment →
- Paint and fillers: fineness is expressed in microns or mesh; fine micronised products are preferred. Micronised quartz →
Choosing the right size directly affects the performance of your product.
Conclusion
In summary, the grain size of silica sand ranges from microns to millimetres and is expressed in microns, mesh or AFS depending on the industry. Being able to convert between these units is the first step in choosing the right product. To determine the right grain size and fraction for your application, please get in touch with us.