Introduction

Due to the national supply chain interruption following the COVID-19 Pandemic, Mindware Technologies has experienced a shortage of pre-wetted Galvanic Skin Conductance (GSC) electrodes. For continuity of data collection during the shortage, Mindware Technologies has explored other electrode options (i.e., independent variable) to ensure reliable GSC reading against our typical pre-wetted GSC electrodes (i.e., dependent variable). After extensive testing, manually wetting dry GSC electrodes with conductive paste using the procedure described below proved most reliable. This article contains a step-by-step guide outlining the proper protocol and procedures to wet dry GSC electrodes so that there will be no statistically significant differences in data sets containing a mix of participants who had pre-wetted vs. dry GSC electrodes applied.

Differences Between Pre-Wetted and Dry Electrodes

If you have previously purchased GSC electrodes from Mindware Technologies, in the context of this article these electrodes will be referred to as pre-wetted electrodes. As you can see in the photo above, the electrode labeled 1 is a pre-wetted GSC electrode. Pre-wetted electrodes are one-time-use disposable electrodes that once peeled from their plastic case expose the pre-wetted conductive paste on the electrode sponge. Conversely, the electrode labeled 2 in the photo above will be referred to as dry GSC electrodes, those newly available for purchase. Dry electrodes are also one-time-use disposable GSC electrodes; however, once peeled from their plastic case they expose a dry electrode sponge.

Dry electrodes will require the researcher to manually wet their electrodes with conductive paste before applying the electrodes to the participant. This process is relatively quick, and is explained in detail below.

Acquiring Data Using Dry Electrodes

Materials Needed

The following materials will be needed to properly wet dry GSC electrodes:

1. Pouch of dry GSC electrodes
2. 4oz bottle of conductive paste
   Note: This exact paste is important to maintaining consistant recordings
3. 1mL syringe
4. 2 green electrode leads
   Note: Provided with MindWare hardware, not single use
5. Paper towels

Please see this guide for assistance with ordering the correct quantity of these items for your study

Electrode Prep Procedure

Below describes the protocol which yielded the most reliable dry electrode GSC readings compared to pre-wetted GSC electrodes. Please follow the steps below as closely as possible:

1. Open the bag of dry GSC electrodes and remove 1 plastic strip of electrodes. Each strip will contain 5 dry GSC electrodes
   
2. Take the 2 green GSC electrode leads and snap them into 2 of the metal snaps of the dry GSC electrodes
   
3. Remove one 1mL syringe from the plastic packaging for each new participant
   
   Note: We recommend using and disposing of one 1mL syringe for each new participant. In the spirit of disposable, one-time-use electrodes like pre-wetted GSC electrodes, throwing each syringe away reduces the need to make IRB revisions on sanitizing procedures for multi-use syringes.
4. Unscrew the white plastic top of the conductive paste bottle. Insert an empty 1mL syringe into the paste such that the tip of the syringe is submerged in paste with the plunger fully depressed. Begin to pull back on the syringe plunger so that 1mL of conductive paste is suctioned into the syringe. Securely screw the white plastic top of the conductive paste back onto the bottle when done.
   
5. Use the paper towel to wipe off any excess paste on the outside of the syringe.
   
6. With the electrode leads clipped in, peel the 2 dry electrodes from the plastic strip. Place the electrodes on a dry, even surface with the adhesive side of the electrode face up.
   
7. Use the 1mL syringe to apply .28mL of conductive paste to each electrode. Use the markings on the syringe to guide your precise measurement of paste applied.
   
   Apply the gel so that it covers as much surface area of the sponge as possible. Do not build a mound of paste on sponge, rather spread the application of gel across the sponge as much as possible.
   
   Note: Apply gentle pressure to the syringe applicator when releasing paste from the syringe. The syringes are very sensitive to pressure.
8. Take the manually wetted electrode and press the adhesive side to the desired location on the participant (e.g., palms of hands, finger tips, shoulder blades, etc.). If any paste comes loose from underneath the electrode during adhesive application, use a paper towel to wipe excess gel away to prevent electrode bridging.
   
9. Plug the electrode leads into your respective Mindware equipment and begin acquisition!

Data Collection

Data collection has been validated against pre-wetted electrodes when following this procedure. The signal quality and characteristics will be indistinguishable from existing GSC data collected.

Further Information

Please visit our Skin Conductance (EDA) Training Guide for additional resources and information!