White film on gelfree electrodes – cleaning and maintenance advice
JAraneda
Chile
in Electrodes
Hello OpenBCI community,
I’m using an OpenBCI All-in-One Gelfree Electrode Cap Bundle, and after several sessions I’ve noticed the formation of a white / opaque film on the metallic surface of some electrodes.
This film:
- Appears after normal use (EEG recordings)
- Does not come off with isopropyl alcohol
- Looks like a thin mineral or oxidation layer rather than dirt
I suspect it could be related to sweat residues (salts) or mild surface oxidation, but I’d like to confirm.
I have a few questions:
- Is this a known or expected effect with gelfree electrodes after repeated use?
- What is the recommended cleaning procedure in this case?
- Is it safe to occasionally use a diluted vinegar (acetic acid) solution, followed by distilled water, to remove this film?
- At what point should this be considered normal wear vs. electrode degradation affecting impedance and signal quality?
For context:
- Electrodes are cleaned after use
- Stored dry
Any guidance from OpenBCI staff or experienced users would be greatly appreciated.
Thank you in advance!
Best regards,
Juan
Comments
Juan, hi.
If you have not already, please reach out to Customer Service via email (contact at openbci.com) to open a ticket.
How 'hard' is your tap water there in Chile? In other words (if this is well water) are there dissolved minerals in the water such as calcium? To my eye this looks like hard water deposits. Do you see such deposits on other kitchen items you use such as glasses, containers etc, that after washing are allowed to air dry with some water still on the surface?
With air dried kitchen items, some acidic solutions such as acetic or citric acid can remove deposits. However with the electrodes, these are composed a various layers: typically a plastic substrate, then plated with silver, then 'chlorided' with silver chloride. Silver as you know is shiny. The chloride layer makes it appear grey or dark. My anxiety would be that any form of acidic solution might remove the chloride layer.
From your photo it does appear the deposits are forming where droplets of water are allowed to evaporate.
Have you considered a rinse or spray with distilled water before allowing the electrodes to dry?
Are you still seeing expected impedances? In other words has the impedance degraded over time, since they were new?
Regards, William