When mounting Pt or Mo apertures, please note:
Very small and loose particles may contaminate new and well made apertures. Inspect aperture, after placing it flat side up on a clean watch glass. Use a light microscope with a 10 to 40 x objective.
If required, ultra-sonicate aperture in absolute alcohol and blot, flat side up on filter paper. Work with aperture container and electron microscope holder above lint free material, such as aluminium foil or a large filter paper.
Use tweezers, exerting little pressure, and lift aperture straight into aperture holder.