The Electrode Puller

The first step in making electrodes is to "pull" them with an electrode puller. This is a device that applies constant tension on a glass capillary tube while heating it. As the glass heats up it gets soft - the tension provided by the puller arm stretches the weakened area until it eventually breaks. This produces a very fine point on the capillary tube.

The shape of the tip is very important. It can be very long and drawn out or blunt. This is determined by two factors, the temperature of the heating element and the amount of tension used to pull the glass.

In modern electrode pullers, both of these factors can be computer controlled and are set by the user. Our puller can only vary the temperature of the heating element, so we adjust this to achieve the proper tip.

The procedure for doing this is:

1. Break a piece of capillary tube off the stock that is about 3" long.

2. Pull the puller arm back (to the left) and put the tube into the puller arm. Carefully advance the puller arm to the right until the tube goes through the heating element and unto the holder shelf. Be very careful here because the glass tube can rip the heating element if it's not lined up well and you move it too quickly. When the arm has moved far enough to the right it will click into place. About 1/4 inch of the capillary tube should stick off the back of the holder shelf.

3. Close the holder on the end of the tube.

4. Push the start button.

The pulling will take a while ( a minute or two) so don't get anxious. When the puller snaps back, remove the two new electrodes and put them in the temporary storage petri dish.

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