1. Remove the external insulation and spread each strand as shown in Fig. 1. This makes sure that each strand will come in contact with the NaOH-NaCl solution.
2. Put NaOH and NaCl in a metal plate with 1:1 to 3:1 ratio. NaCl lowers the melting point of the solution. Heat the plate until the solution is liquid and transparent.
3. Place the exposed part of the wire inside the solution. Make sure that every strand is submerged and gently stir it. The solution will turn to white and then back to transparent.
4. The end result is shown in Fig. 5. The insulation has been removed, but the copper has merged with salts.
5. Prepare some water for boiling in a metal utensil. Submerge the wire inside the water until the salts has been resolved.
6. Wire is ready. Insulation has been removed from each strand, without hurting the copper. Solder the wire to prevent copper oxidization.
The solution can be used multiple times, until it turns white permanently and black spots from burn insulation becomes visible.
WARNING: NaOH is highly caustic! In case it comes in contact with skin or eyes rinse with plenty of water and call a medical professional.