Particle size is the parameter that appears on almost every botanical extract specification and is understood on almost none of them. It is written as a single number — 80 mesh, 100 mesh — as though that described a powder, when in fact it describes one point on a distribution, measured by a method that is rarely stated, against a standard that is rarely named. Two materials both sold as "80 mesh" can behave very differently in the same filling line. This guide covers what a mesh figure means, why the same material gives different numbers in different laboratories, and which process outcomes the particle size distribution actually governs.
What a mesh figure describes
Mesh is a count, not a size. A US mesh number refers to the number of openings per linear inch in a test sieve, so the higher the number, the finer the powder. Converting that to a physical dimension depends on which mesh standard is being used, because US, Tyler and British Standard sieves are not identical. The practical ladder runs like this. A 20 mesh sieve is roughly 850 µm, and its material is coarse herbal cut, sometimes sold as tea material; 40 mesh, at about 425 µm, is a coarse extract powder used where dusting is a problem; 60 mesh, at about 250 µm, is the standard extract powder for dry blending; 80 mesh, at about 180 µm, is the most commonly quoted extract specification in international trade; 100 mesh, at about 150 µm, is a fine grade for encapsulation and tableting; 140 mesh, at about 106 µm, serves suspension and colour-critical work; 200 mesh, at about 75 µm, is very fine, and there flow and dust control become the constraint; and 325 mesh, at about 45 µm, is micronised material for specialist applications, carrying dust-explosion precautions.
The openings are nominal, and the standards differ slightly at the same mesh number. If the specification says only "80 mesh" without naming the standard, it is not reproducible, and the first supplier to test against a different sieve stack will produce a figure that looks wrong without anyone having made a mistake.
"Through 80 mesh" is not the same as "80 mesh"
This is the single most common misreading in the category, and it costs buyers real money in rejected batches.
A pass-through specification says that a stated proportion of the material passes a given sieve — for example, not less than 95% through 80 mesh. That permits an unlimited quantity of fine material below the sieve: the powder can be almost entirely fines and still comply.
A cut specification describes material held between two sieves, for example 80 to 100 mesh. That defines a window and controls both the coarse and the fine ends.
A single number, used alone, is ambiguous between the two. It also says nothing about the quantity of fines, which is the fraction that causes dust, segregation and caking. Where a supplier quotes one figure, ask three follow-up questions: what proportion passes, what proportion is retained on the next sieve down, and was the analysis done on an as-is or a dried sample. Moisture changes the result, and a hygroscopic powder can measure differently depending on how long it has been exposed to air before testing.
Why two laboratories disagree about the same powder
Two method families dominate, and they answer the question differently.
Sieve analysis is the classical approach: a stack of certified sieves is agitated for a defined time, and the mass retained on each is reported. It measures the smallest cross-section that will pass an aperture, which means a long, needle-shaped particle can pass a sieve that a spherical particle of the same mass would not. Agitation method and duration affect the result, so the method has to be part of the record. Certification of the sieves matters too — a worn sieve is a slow, invisible error.
Laser diffraction reports a distribution derived from light scattering, usually as a set of percentiles such as D10, D50 and D90, where D50 is the median particle size. It is fast, it repeats well, and it assumes a particle shape and a refractive index. For irregular botanical powders, that assumption is an approximation, and the resulting figures can differ systematically from sieve data — sometimes by enough to look like a different product.
Neither method is wrong. They are not interchangeable, and comparing one supplier's sieve result with another's laser result is comparing two measurements rather than two materials. The specification should name the method, the standard and the sample preparation, and the buyer should insist on the same triad from every supplier.
What particle size actually changes
Flow and dosing and dust generation are the first two effects, and both are decided on the filling line. Fine powder flows poorly and bridges in hoppers, while coarse powder flows better at moderate sizes but can hang up if it is very coarse — and fill weight accuracy on a high-speed line depends on exactly this. Fines also generate a great deal of dust, with a dust-explosion risk below roughly 50 µm, whereas coarse material produces little; operator exposure and containment costs follow the dust rather than the sieve number.
Segregation in a blend and wetting behaviour come next, and they pull in opposite directions. Fines sift downward through a coarser component while coarse particles rise, and the outcome is sachet-to-sachet variation even from a blend that looked homogeneous. Fine powder wets quickly but tends to form surface lumps; coarse powder wets slowly and shows visible grit if it fails to dissolve. Both of those reach the consumer as complaints about floating powder or sediment.
Colour perception and tableting are where the process meets the finished product. In many materials a fine powder gives higher colour strength per unit weight, so the dosage needed to hit a colour target shifts with particle size. On a tablet press, fines compress better but generate more dust, while coarse material compresses poorly and flows better; direct compression routes are sensitive to that difference.
Caking and handling losses are the storage and yield consequences. Fine powder has a higher surface area and takes up more moisture, which makes water activity control more important at fine sizes, while coarse powder takes up less moisture but holds more air between particles. Fines also adhere to surfaces and packaging while coarse material stays free-flowing with less retention, so yield accounting differs between grades.
The pattern is that no single direction is "better". Finer improves colour strength, wetting speed and compressibility while worsening flow, dust and caking. Coarser improves flow and dust while worsening dissolution and colour uniformity. The specification should therefore be derived from the process, not from a generic preference.
Matching particle size across a blend
Where a botanical extract is one component of a dry blend, its particle size and bulk density have to be matched to the other components, or the blend will separate between the blender and the sachet. Segregation is driven by differences in size and density, and it is rarely caused by the blender.
The controls are practical: specify a distribution rather than a single mesh figure for each component, require bulk density alongside it, add a granulation or binder step where components differ sharply, and verify with in-line uniformity checks across the run rather than at the start alone.
Writing the specification
A usable particle size specification carries five elements: the method (sieve analysis or laser diffraction, with the standard named), the statistic being controlled (a pass-through percentage, or a percentile such as D50 with a tolerance), the limits, the sample preparation, and the test frequency. Where the material is hygroscopic, add the water activity or moisture condition at which the test is performed.
Where the material is a granulated or agglomerated grade, remember that the particle size describes the granule, not the primary particle inside it. A granulated product can be coarse on the sieve and instant in the glass, which is the entire point of granulating it — so the dispersion test belongs alongside the particle size figure, not instead of it.
Frequently Asked Questions
What is 80 mesh in microns?
Approximately 180 µm opening on a US mesh sieve. The exact figure depends on the mesh standard, since US, Tyler and British Standard sieves differ, so the standard should be named alongside the number.
Is "80 mesh" the same as "95% through 80 mesh"?
No. A pass-through specification permits an unlimited fines fraction, and a bare mesh figure does not say whether a pass-through or a cut specification is intended. Ask what proportion passes, what is retained, and what the fines content is.
Why do my sieve results differ from the certificate's laser results?
Because the two methods measure different things and make different assumptions about particle shape. For irregular botanical powders the difference can be systematic. Compare like with like, and specify one method for all suppliers rather than accepting whichever figure you are given.
Does a finer powder dissolve better?
Not necessarily. Finer material wets faster but is more prone to forming lumps on the surface of water, because the outer layer hydrates before the core disperses. Dissolution depends on wettability and on the dispersion system as much as on particle size, which is why granulated grades often outperform a fine milled powder in a drink mix.
What particle size should I specify for a capsule?
A common starting point is 100 mesh or finer with a stated fines content, because capsule filling tolerates fines better than it tolerates coarse particles. The binding constraint is usually flow on the filling machine, so set the target from the equipment, then confirm it with a trial run rather than from a generic recommendation.
Specify particle size with DayNatural
DayNatural supplies botanical extracts and powder systems across the mesh range, including standard milled, fine and granulated grades, with the method, standard and distribution stated on the specification and dispersion behaviour tested in the intended medium. All documentation is verified through our Mérieux NutriSciences testing programme.
