While saline solution is not strictly required for use with sponge electrodes, it is recommended. Plain water will work in helping the sponge to pass current, just not as well as saline solution. Water in and of itself is a very poor conductor of current. So in using just water, you’re essentially asking the sponge alone to work to pass current to the targeted area. By adding salt to plain water (saline solution), the electricity is able to actually jump from molecule to molecule through the solution, providing a better connection. In using a sponge well soaked with saline solution, the current encounters the least amount of resistance, providing the most effective, and most comfortable tDCS experience.

tDCS electrode sponges can be replaced every two weeks or after seven tDCS sessions. However, for optimum performance and hygiene reasons, we recommend replacing your sponges after each session. Replacement sponges for 2×2 and 3×3″ electrodes can be purchased in packs of 10 in our online store. In addition, due to customer requests we now offer replacement sponges in subscription plans at discounted pricing.

Over time, the sponges within sponge electrodes can grow brittle and crumble, crack, or split, causing an uneven distribution of current. Worn-out sponges can cause an uncomfortable tDCS session, with increased tingling, itching, and sometimes stinging sensations occurring. A good way to tell if your sponges need replacing is if soaking them with saline solution becomes more difficult, if they start to display a darker/brownish color, or begin feeling “stale.”

More importantly, if your tDCS sessions become uncomfortable, or you start to notice sensations that maybe you didn’t before, this is a good sign that your sponges need replacing. You can find 10-packs of replacement sponge inserts for both the 3×3″ Amrex Electrodes and the 2×2″ Amrex Electrodes in our online store.

• 10pk 3×3″ replacement sponges
• 10pk 2×2″ replacement sponges

Essentially the main difference between the 3×3″ Sponge Electrodes and the 2×2″ Sponge Electrodes is the size of the electrode pad and the area they cover. They both are constructed in exactly the same way, with the same materials and use the same Amrex electrode cables and adapters. The 3×3″ electrodes will cover a broader area, while the 2×2″ will cover a slightly smaller, more condensed area. Essentially the 2×2″ sponge electrodes will stimulate a more targeted area, while the 3×3″ have more of a generalized effect on the area being stimulated. Additionally, because of the larger surface area, the 3×3″ size generally provides a more comfortable session with fewer negative side effects. Due to these facts, the 3×3″ size sponge electrodes are far more popular than their 2×2″ counterpart.

We no longer recommend using self-adhesive electrodes with tDCS. The reason we do not recommend self-adhesive is due to the fact that they do not conduct current as well, or as evenly as sponge electrodes. Due to the way self-adhesive Electrodes are manufactured, there’s often a high potential for current to collect, or concentrate, on a specific location on the electrode’s surface. This concentration of current creates what’s known as a “Hot Spot,” causing high current density which can result in an uncomfortable session, or even skin irritation. While Hot Spots do not always happen, sponge electrodes are by far the safest and most effective option for use with tDCS. Additionally, you can further practice “safe-tDCS” by always using an electrode positioning headband(s) (we offer small and large tDCS headbands), to ensure that the entire electrode makes contact with the targeted area.