Hot wire for rear glass of almost all cars is printed on the surface of glass used conductive silver paste by screen printing. After tempered, conductive silver paste is sintered on the surface of glass. Because of having resistance, it can clean the fog after electrified.

There are three deciding factors for hot wire power:
Pattern of hot wire: It's best more than 1mm of width to be better printed.
Film's thickness of silver paste: Film is thicker, and power is less.
The silver content effects directly the resistance of hot wire. 

Model Item SL-60 SL-70 SL-80
Silver Content 60% 70% 80%
Resistance Ω 7.0-8.0 5.0-6.0 4.0-5.0