---
title: "What is a Spark plug made of?"
description: "A ceramic insulator carrying a centre electrode of nickel, platinum or iridium inside a steel shell. Every component, the material it uses, and the constraint that m"
url: https://atoneplace.net/made-of/spark-plug/
site: "At One Place"
---

# What is a Spark plug made of?

**What is a Spark plug made of?: A ceramic insulator carrying a centre electrode of nickel, platinum or iridium inside a steel shell.**

A plug's "heat range" is not about how hot a spark it makes but about how fast it conducts heat away, set by the length of the insulator nose. Too cold and the tip fouls with carbon; too hot and it becomes a glow plug and pre-ignites the mixture, which can destroy a piston. Iridium and platinum plugs last far longer, sometimes over 150,000 km, because the fine centre wire erodes slowly — the ordinary nickel plug wears its gap open and the ignition system eventually cannot bridge it. Torque matters more than most people expect: overtightening distorts the shell and changes the heat path, and the manufacturer's figure always takes priority over a generic chart.

## Component by component

*Every material is a choice, and the third column is the constraint that drove it.*

| Part | Material | Why that material |
| --- | --- | --- |
| insulator | sintered aluminium oxide ceramic | It has to insulate against 20,000-40,000 volts while conducting combustion heat away and surviving 900 °C — almost nothing else does all three. |
| centre electrode | nickel alloy with a copper core, tipped with platinum or iridium in long-life plugs | Copper conducts heat out of the tip; iridium melts near 2450 °C and erodes slowly, so a very fine tip can survive and it needs less voltage to fire. |
| ground electrode | nickel alloy welded to the shell | It must hold its position within tenths of a millimetre while glowing hot, because the gap sets the required firing voltage. |
| shell | plated steel with a rolled thread and a sealing washer or taper seat | The shell carries the earth path and the clamping load, and must seal a combustion chamber at 100 bar. |
| internal resistor | a carbon or glass resistive seal, typically 5 kΩ | It suppresses the radio interference the spark generates, which is why fitting a non-resistor plug can upset the engine electronics. |

## Other cars and driving objects

- [Car tire](https://atoneplace.net/made-of/tire/) — Several different rubber compounds reinforced with steel and textile cord — closer to a composite than to rubber.
- [Car battery](https://atoneplace.net/made-of/car-battery/) — Lead and lead dioxide plates in dilute sulfuric acid, in a polypropylene case — mostly lead, by weight.
- [Airbag](https://atoneplace.net/made-of/airbag/) — A coated nylon bag inflated by a small solid-propellant gas generator in about thirty milliseconds.
- [Brake pad](https://atoneplace.net/made-of/brake-pad/) — A friction compound of fibres, fillers and resin, moulded and bonded onto a steel backing plate.
- [Windshield (windscreen)](https://atoneplace.net/made-of/windshield/) — Two sheets of ordinary glass laminated to a tough plastic interlayer, which is what stops it falling out.
- [Seatbelt](https://atoneplace.net/made-of/seatbelt/) — Woven polyester webbing designed to stretch a controlled amount, plus a locking retractor and a pyrotechnic pretensioner.

## Common questions

### What is a Spark plug made of?

A ceramic insulator carrying a centre electrode of nickel, platinum or iridium inside a steel shell.

### What is the insulator of a Spark plug made of?

Sintered aluminium oxide ceramic. It has to insulate against 20,000-40,000 volts while conducting combustion heat away and surviving 900 °C — almost nothing else does all three.

### What is the centre electrode of a Spark plug made of?

Nickel alloy with a copper core, tipped with platinum or iridium in long-life plugs. Copper conducts heat out of the tip; iridium melts near 2450 °C and erodes slowly, so a very fine tip can survive and it needs less voltage to fire.

## Related pages

- [Car tire](https://atoneplace.net/made-of/tire/)
- [Car battery](https://atoneplace.net/made-of/car-battery/)
- [Airbag](https://atoneplace.net/made-of/airbag/)
- [Brake pad](https://atoneplace.net/made-of/brake-pad/)
- [Windshield (windscreen)](https://atoneplace.net/made-of/windshield/)
- [Seatbelt](https://atoneplace.net/made-of/seatbelt/)
- [Pencil](https://atoneplace.net/made-of/pencil/)
- [Tennis ball](https://atoneplace.net/made-of/tennis-ball/)
- [Banknote](https://atoneplace.net/made-of/banknote/)
- [Golf ball](https://atoneplace.net/made-of/golf-ball/)
- [Paper](https://atoneplace.net/made-of/paper/)
- [Glass](https://atoneplace.net/made-of/glass/)

## Sources

- Official vendor product documentation — At One Place (/about/)