This article needs additional citations for verification. (March 2015) |
A flame is affected by the fuel introduced and the oxygen available. A flame with a balanced oxygen-fuel ratio is called a neutral flame. The color of a neutral flame is semi-transparent purple or blue. This flame is optimal for many uses because it does not oxidize or deposit soot onto surfaces.
Oxidizing flame
editIf the flame has more than enough oxygen, an oxidizing flame is produced. When the amount of oxygen increases, the flame shortens due to quicker combustion, its color becomes a more transparent blue, and it hisses or roars.[1] With some exceptions (e.g., platinum soldering in jewelry), the oxidizing flame is usually undesirable for welding and soldering, since, as its name suggests, it oxidizes the metal's surface.[1] The same principle is important in firing pottery.
Reducing flame
editA reducing flame is a flame with insufficient oxygen. It has an opaque yellow or orange color due to incandescent carbon or hydrocarbons[2] which bind with (or reduce) the oxygen contained in the materials the flame processes.[1] The flame is also called carburizing flame, since it tends to introduce carbon soot into the molten metal.
The flame also produces carbon monoxide, a poisonous gas which burns on the outer envelope of flame into carbon dioxide.[3]
Reducing flames with no carbon
editReducing flames using zero-carbon fuel, such as reducing hydrogen flames, are exceptions. They don't have an opaque yellow or orange glow, nor do they produce soot or carbon monoxide.
See also
edit- Oxy–fuel welding and cutting § Types of flame for further details about the above types of flame in oxy-fuel burners
- Flame test
- Oxygen
- Oxyhydrogen
- Redox
- Spark testing
References
edit- ^ a b c "The Anatomy of a Flame", in: "Jewelry concepts and technology", by Oppi Untracht, 1983, ISBN 0-385-04185-3
- ^ "Brass Melting in Gas Furnaces". The Gas Age. 45. Robbins Publishing Company: 196. February 25, 1920. ISSN 0096-0780. Retrieved 2015-01-01.
- ^ "Combustion of hydrocarbon fuels - Fuels - Edexcel - GCSE Chemistry (Single Science) Revision - Edexcel". BBC Bitesize. Retrieved 2025-10-18.