A sieve analysis is a table that says what percentage of a bead batch sits between each pair of screen sizes. It looks like paperwork, but to someone who reads it, it is a preview of how the beads will behave on the road or in the mill. Here is the plain-English version of what those rows mean.
Mesh and microns, the two languages of size
Mesh is the count of openings per inch in a screen. Forty mesh means the screen has roughly 40 openings per linear inch, and particles that pass through are smaller than those openings. Because more openings means smaller holes, higher mesh always means finer beads. The same size is often quoted in microns: one micrometer is one thousandth of a millimeter, and 40 mesh corresponds to roughly 425 micrometers.
Suppliers switch between the two systems freely, which is where half the confusion starts. A customer asks for “20 to 40 mesh”, another asks for “850 to 425 micron”, and they are describing the same product. When in doubt, ask for the micron range, because it is unambiguous.
What the percentages tell you
A single cut like 20/40 mesh still contains a spread of sizes inside that window. The sieve report breaks it down: so many percent above 850 microns, so many between 850 and 600, and so on down to the fines below the bottom screen. Two suppliers can both call their product 20/40 mesh and ship noticeably different distributions, one heavy on the coarse end, the other with more fines. Both pass a loose description; only one is right for your job.
For drop-on road marking beads, a batch with too many fines reflects weakly, because small beads catch less light. For grinding media, an uneven distribution changes how the charge packs in the mill. That is why we include the full sieve report, not just the nominal range, and why a careful buyer reads the middle of the table, not just the top line.
Three numbers to look at first
Check the top oversize row: a compliant batch should have close to zero percent above the top screen, since oversized beads settle unevenly or clog the line. Check the middle of the distribution: the bulk of the material should sit in the intended working range rather than at the edges. And check the fines at the bottom: for most marking jobs, a few percent of fines is tolerable, but a creeping fines number usually means the screening is drifting and tomorrow’s batch may be worse than today’s.
Ask for the report before the quote
Any serious supplier keeps sieve data for every batch and can share it before you commit. If a supplier hesitates or quotes only a nominal mesh, that is worth noticing. The report is free, it takes two minutes to produce, and it saves both sides from a dispute at the site gate.