Every week a new inquiry lands in our inbox that starts with a number and a question mark: “20 mesh?” “100 mesh?” Usually the customer has been told a mesh number by someone who read it off an old datasheet, and they are not sure what it means for their job. Fair enough. Mesh is a confusing system, and it works backwards from what you would expect.
The one rule that fixes everything
Mesh counts how many openings per inch in the sieve. More openings means smaller holes, which means smaller beads. So 20 mesh is coarse, roughly 850 micrometers, and 200 mesh is fine, around 75 micrometers. If someone quotes you 20/40 mesh, they mean the beads fall between those two sieve sizes, from about 850 down to 425 micrometers. The higher the number, the finer the product. New buyers get this backwards all the time, and it costs them a batch that is the wrong size for the line.
Matching size to the marking job
Drop-on beads for road markings usually sit in the 20 to 140 mesh range, with the most common grades clustering around 20/40 and 20/100. The coarser beads stay on top of thick thermoplastic and give strong initial reflectivity. Finer beads are used where the paint film is thin, like spray-applied cold plastic, because a big bead has nothing to sink into and gets knocked off by traffic.
AASHTO M247 Type 1, the drop-on grade most US jobs reference, runs roughly from 1180 to 150 micrometers, which is about 16 to 100 mesh territory. EN 1423 drop-on beads fall in a similar band. We produce several standard cuts and can make custom distributions when a project calls for something between the usual sizes.
What happens when you pick wrong
Too coarse for a thin paint film: beads sit proud of the surface, traffic snaps them off, and within weeks the line is dotted instead of solid. Too fine for a thick thermoplastic line: beads sink below the surface and reflect almost nothing, so the contractor gets a line that looks fine in daylight and disappears at night. Both failures get blamed on the paint or the crew, but the real culprit is usually a mesh spec pulled from a different job.
A practical starting point
When a customer sends us a marking method, we can usually narrow the choice without a long back-and-forth. Thermoplastic, sprayed or screeded thick, take a coarser drop-on grade. Paint or cold plastic sprayed thin want a finer cut. If the job has a standard attached, we match the standard’s sieve table exactly and send the report with the batch.
Not sure which end to start from? Write down the marking material, the application thickness, and the country where the road is, and send it over. We will suggest a mesh and, if you want, send a sample bag first so you can run it through your own rig before committing to a container.