Syringe Filters

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Use 0.22μm sterile PTFE syringe filters

You can potentially replace the PTFE material with Nylon, however there appears to be less data indicating safety, and this should require more research.

Details

Pore Size: 0.22μm (this size is required for sterilization)
Sterility: Use pre-packaged, sterile filters.
Size: if you’re filtering 1-10mL, use a 13mm filter. 10-100mL use a 25mm filter¹. 100m-250mL use a 33mm filter². Larger is generally easier to push though.
Filter material: Polytetrafluoroethylene (PTFE) is moderately available and is compatible with our goals. It is safe with oil, benzyl alcohol, and benzyl benzoate³ ⁴. Nylon filters may also be a good choice, but require more research to verify.
Hydrophobic or Hydrophilic: Unclear, but both likely fine for an oil based solution. I’ve only used hydrophilic.

Don’t use PVDF of PAS

Benzyl benzoate, an ingredient in the brew, can cause PVDF filters to dissolve. This could have potential side effects such as filters breaking or PVDF leeching into the filtered solution. There is minimal data to support whether PVDF is safe, so in this case it’s best to air on the side of caution⁵.

Bubble Point

Many, but not all, filters will list a bubble point or “max burst pressure”. Check or confirm this bubble point by testing the bubble point of your filters with a sample of your solution. Bubble points can change when the filters are pre-wetted with different solutions, so always check with your actual brew.

Read more about bubble point testing here.