Conflicting Advice Regarding Regular Salt "Baths"

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peteralynn
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Joined: Thu Jul 19, 2012 2:41 pm

Conflicting Advice Regarding Regular Salt "Baths"

Post by peteralynn »

Hello BioSemi,
We purchase our BioSemi equipment through Cortech Solutions out in North Carolina (USA). Recently, we added an additional lab, and the technician who came out to help install it recommended that we regularly (every two weeks or so) soak our electrode braids for five minutes or so in a salt water bath. However, between your manual and many other posts on these forums, it seems to me that soaking is only recommended for particularly noisy electrodes (likely at the end of their life) and otherwise NOT recommended (viewtopic.php?f=1&t=649). From the Cortech Manual, the only justification I can see for a regular soak (besides trying to prolong the functionality of a dying braid) is to eliminate the few minutes of noise observed at the beginning of some recordings:

"(2) If the signal starts out noisy but becomes quiet over the course of 3-5 minutes:
This is most likely a sign that the electrodes started out dry and it took a few minutes for the moisture to penetrate the hard electrode material. 3-5 minutes of slightly noisy signals when starting out with dry electrodes is within the expected range of normal operation. To avoid this initial noisy period, try soaking your active electrodes in salt water for 5 minutes once a week or for 5 minutes before each recording session. IMPORTANT: Soaking active electrodes in any liquid for longer than 10 minutes at a time is inadvisable as moisture will penetrate the electrode pellets and accelerate corrosion (loss of electrode material), resulting in poor electrode performance."

If you could reiterate BioSemi's official stance on the salt soak (perhaps giving special treatment to the justification cited above, as well as explicating precisely what such a soak accomplishes on a chemical level), I would be much obliged.

Gratefully,
Peter Lynn

Coen
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Re: Conflicting Advice Regarding Regular Salt "Baths"

Post by Coen »

Soaking is only recommended in case of noise problems, and as a method to identify defect and/or noisy electrodes.

In case of noisy electrodes, soaking the electrodes in water for a few hours may sometimes "repair" the electrodes. If no improvement in noise is seen after a few hours, then further soaking is not worthwhile

We do not recommend soaking as regular maintenance, although we have not seen any adverse effects either. It just does not improve anything.

You are correct that soaking prior to application on the subject may speed up the initial stabilization of the skin-gel-electrode interface a bit. However, it won't eliminate the initial instability completely because some minutes are required anyway for the gel to penetrate the upper layers of the skin. This makes the soaking procedure generally not worth the extra effort.

Best regards, Coen (BioSemi)

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