Insulation varnish selection with wires and other insulation material selection relies on its motor insulation class, say motor insulation class F, the wires, varnish, paper, wedge etc should takes the corresponding insulation class. 
Insulation varnish is normally composed of varnish base, solvent or diluent and auxiliary material, by its application and status, it can be divided into 4 different kinds, as dipping varnish, covering varnish, silicon varnish, corona proof varnish.
Insulation class is divided into 7 different kinds, as Y class, A class, E class, B class, F class, H class, and C class.
listing them in particulars :
Insulation class: max allowable working temperature

Y class:90 ℃, non-dipped material as cotton yarn, silk or paper or its composition.
A class:105℃, dipped material or material in the liquid dielectric (say the cotton yarn,silk or paper etc and its composition) in the transformer oil

E class:120℃ compound organic film, cermaic paint or its composition.
B class:130℃
F class:155℃
H class:180℃, resin (organic silison resin)adhesive, or dipped, coated mica, fiber, asbestos or its composition
C class:180℃ above, resin adhesive or the dipped, coated mica,fiber and non-dipped,non-processing mica, ceramic, quartz or its composition.

The stator varnish machine design, the insulation class of your motor is one factor we should know, besides your varnishing products size, the shift Qty, curing time and other special request.