Oxidizing and reducing flames
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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.[1] This flame is optimal for many uses because it does not oxidize or deposit soot onto surfaces.
Oxidizing flame[edit]
If the flame has too much 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/roars.[2] 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.[2] The same principle is important in firing pottery.
Reducing flame[edit]
A reducing flame is a flame with insufficient oxygen. It has an opaque yellow or orange color due to carbon or hydrocarbons[3] which bind with (or reduce) the oxygen contained in the materials the flame processes.[2] 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.[4]
Reducing flames with no carbon[edit]
Reducing zero-carbon fuel flames, 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
- Oxyhydrogen
- Redox
- Oxygen
- Flame test
- Spark testing
References[edit]
- ^ HHO gas generator, Typ: H2-3 (BlackWater) 1500 L/hour, retrieved 2021-12-24
- ^ a b c "The Anatomy of a Flame", in: "Jewelry concepts and technology", by Oppi Untracht, 1983, ISBN 0-385-04185-3
- ^ "Gas Age". Gas Age: Combining Natural Gas, Gas Age, Gas Record. 45. Robbins Publishing Company: 196. 1920. ISSN 0096-0780. Retrieved 2015-01-01.
- ^ "Combustion of fuels - Products and effects of combustion - GCSE Chemistry (Single Science) Revision - Other". BBC Bitesize. Retrieved 2021-12-24.