The voltage and arc length are closely related. The shorter the arc, the lower the arc voltage and the lower the temperature produced, an as the arc lengthens, the resistance increases, thus causing a rise in the arc voltage and temperature.
Most shielded metal arc welding electrodes have chemicals added to their coverings to stabilize the arc. These arc stabilizers form conductive ions that make the arc more stable and reduce the arc resistance. This makes it easier to hold an arc. By lowering the resistance, the arc stabilizers also lower the arc temperature. Other chemicals within the gaseous cloud (shield gas) around the arc may raise or lower the resistance.