Which statement correctly identifies the designation of the 75-μm sieve?

• A. The 75-μm sieve is designated as #200.
• B. The 75-μm sieve is designated as #50.
• C. The 75-μm sieve is designated as #300.
• D. There is no standard designation.

Answer: (A)

Understanding sieve designations relies on how mesh size and opening diameter relate. In the standard sieve series, the mesh number tells you the approximate size of the openings—the higher the mesh, the smaller the openings. The 200-mesh sieve has openings around 0.075 millimeters, which is 75 micrometers. So a sieve described as 75 μm matches the 200-mesh designation. That’s why this statement is the best one. For context, a 50-mesh sieve has larger openings (about 0.30 mm, or 300 μm) and a 300-mesh sieve has smaller openings (about 0.05 mm, or 50 μm). There is indeed a standard linking micrometers to mesh numbers, so saying there’s no standard isn’t correct.