According the nature of the material, origin m and also particular composition, the values shown in the table can assume a certain range of voltages. The table shows average values and ius useful as starting point in noncritical projects. For critical projects consult the particular characteristics of the material.
| Material | Dielectric strength (kV/cm) |
| Vacuum | 20 |
| Air | 20 to 75 |
| Porcelain | 40 to 200 |
| Paraffin Wax | 200 to 300 |
| Transformer Oil | 400 |
| Bakelite | 300 to 550 |
| Rubber | 450 to 700 |
| Shellac | 900 |
| Paper | 1 250 |
| Teflon | 1 500 |
| Glass | 2 000 to 3 000 |
| Mica | 5 000 |
