At the time of writing, Scotch Brand Electrical Tapes by 3M have discontinued manufacturing the #4 Flatback insulation tape. Gibson has been using the #4 Flatback Scotch insulation tape on just about every pickup model made from early pickup production to present. This has been my favorite tape because of it’s mechanical properties and use in production. The earlier #4 Flatback tape had a slight Olive color tint to it and can be seen on the early P-90s and “Patent Applied For” Humbuckers. The tape made later in production by Scotch is basically black. Here are some other Scotch Electrial Tapes.

#2 tape is a Black Crepe paper tape
#3 is a Natural color Flatback paper tape
#4 is the Black Flatback paper tape
#9 is a Resin/Fibre Crepe paper tape
#38 is an Ivory/Natural color Crepe
After the pickup is wound the finish wire is soldered to the magnet wire, the insulation tape is folded over the solder joint to keep the joint from cutting into the insulation on the magnet wire. If the insulation is broken, the magnet wire could oxidize and break in time. The coil is then wrapped with a layer of .250″ tape and the lead wires are neatly taped into position extending towards the recessed square at the end of the bobbin. The beginning wire is also soldered to the hookup wire that extends through the square opening on the underside of the bobbin. The insulation tape is also folded around the solder joint in the beginning wire to help reduce oxidation or insulation breakdown in the magnet wire.
All of the paper tapes have a Rubber Resin-Thermosetting Adhesive. The standard lengths of the tape rolls are 36, 60 and 72 yards. The width of the tape can be cut to any desired width to be determined by the pickup manufacturer.

The #3 & #4 Flatback tapes can be slit to width with a tolerance of +/- .005″