Prior to soldering, soldered splices must be:

Soldered splices must be joined mechanically before the application of solder. This means that the wires being connected should be twisted together or otherwise secured to ensure a good electrical connection prior to heating them and applying solder. Mechanical joining establishes a strong physical bond that enhances conductivity and provides structural integrity to the splice.

This preparatory step is crucial because soldering creates a reliable joint by filling the gaps between the mechanically joined wires with molten solder, allowing for better electrical contact. If the wires are not joined mechanically beforehand, the solder may not adequately fill the connection, leading to a weak joint that could fail over time.

Other options do not align with the necessary preparation for soldering. While using insulating materials like electrical tape might be relevant after soldering for safety measures, it does not pertain to preparing the splice. Similarly, heating devices or cooling processes are unrelated steps before the soldering occurs. The focus here is ensuring a strong and stable initial mechanical connection, which is vital for effective soldering.