The following method is for cleaning platinum apertures; clean tungsten and molybdenum apertures by heating in vacuum.
Pre-clean apertures by storing them for a while in a strong solvent such as chloroform.
- Place aperture disc in cup or hang strip from hook on cup.
- Turn Bunsen burner to low (small blue flame).
- Hold apertures on flamer 12mm - 20mm above aperture.
- Adjust heat if required to turn aperture bright red. Greater heat and long (more than a few seconds) flaming times increase crystalinity of the disk or strip and eventually ruin the apertures.
- Inspect aperture on a microslide with a microscope. Repeat heating if required.
Note: the force of the heat, rather than the flame itself, cleans the aperture.