Mesh Opening

Mesh opening (often simply called “mesh”) refers to the distance between two adjacent wires in a wire mesh, measured from the inside of one wire to the inside of the next. In other words, it represents the clear opening. For square weaves, the mesh opening is the same in both warp and weft directions. In technical specifications, it is usually stated in millimeters or microns (e.g., 0.25 mm mesh opening). For very coarse meshes, it is also given in mesh per inch (see term: Mesh Count).

The mesh opening is the key parameter used to describe the filtration or screening function of a mesh. For example, a mesh with a 1 mm opening will retain all particles larger than 1 mm; smaller particles can pass through (unless the wire diameter is unusually thick, which would reduce the effective opening). Mesh openings are standardized, particularly for test sieves (DIN ISO 3310) and technical wire cloths (DIN ISO 9044).

Important notes: The mesh opening alone does not always determine the particle size that can be reliably retained—elongated or flattened particles might still pass through if they are oriented just right. That’s why filtration often distinguishes between nominal and absolute filtration ratings.
→ A 100 µm mesh might retain 98% of all particles >100 µm (nominal), but a few narrow 150 µm particles might pass through at an angle.
→ Still, the mesh opening provides an excellent general guide.

Tolerance is another key factor: high-quality mesh has very consistent openings. Lower-grade mesh may have slight variations. For fine screening, this is a quality criterion—manufacturers like GKD maintain tight tolerances using precision weaving and post-inspection processes.

In practice:

• For screening processes, the mesh opening is usually selected slightly smaller than the target separation size to ensure reliable retention.
• In filtration, the mesh opening is chosen based on the smallest particle that must be blocked—often combined with cake formation to capture even finer particles.
• In architectural applications, the mesh opening affects visual transparency:
  → Small openings (<5 mm) appear opaque from a distance.
  → Large openings (≥20 mm) remain visibly open even up close.

Mesh opening should not be confused with pitch (also called “mesh pitch” or “spacing”), which is measured from wire center to wire center. However, in wire mesh, pitch = mesh opening + wire diameter. Standards like ISO 9044 clearly define how to measure mesh opening (typically using a perpendicular microscope projection).

In short: The mesh opening is essentially the “hole size” in the mesh and is a central element of any technical specification. Together with the wire diameter, it determines everything else—flow rate, strength, open area, etc. This makes it a key concept highlighted in any mesh glossary.