Recently, better commercial units have used smaller
(1.5” diameter) sponges in holders that make them easy to
clean and replace. Figures 7 and 8 show a simple design
that will allow our unit to work the same way.
Using a plastic cap from any jar, a stainless steel
fender washer, and some “wire glue,” an excellent
sponge/electrode holder can be made. Make certain your
plastic cap is at least 1.5” in diameter, and cut a
section of sponge 1/4” thick to fit very snugly into
Strip the insulation from perhaps the last 2” of
one of your leads, and feed it into the plastic cap as
Coat one side of a stainless steel or brass washer
with wire glue, and press it into the cap until the
glue dries. This creates a conductive seat when dry
for our sponge to sit on; yet, sponges can be
popped in and out easily for cleaning or
This arrangement would probably work without
the wire glue, and a brass washer could certainly
have the wire soldered directly in place. However,
given the fact that everything will be soaked in salt
water, the wire glue and stainless steel washer have
proven highly resistant to corrosion.
Figure 9 shows the completed sponge
electrodes, and the full unit.
As a quick alternative, you can make a
disposable electrode by just using the wire glue to
attach the wires and “any old” washer directly to the
sponge. Disposable electrodes usually last several months.
You can make a very conductive and durable
homemade wire glue by simply mixing a flexible variety
such as Goop™brand glue with graphite. The more
graphite you can mix into the glue, the better the
conduction (Figure 10).
Important Note: Make absolutely sure to wash new
sponges thoroughly before using them the first time. Many
supermarket sponges have bleach-like preservatives in
them when shipped which can irritate skin! (Don’t ask me
how I know.)
■ FIGURE 8.
July 2017 27
■ FIGURE 9.
■ FIGURE 10.