{{short description|States of a flame}} {{More citations needed|date=March 2015}} thumb|Reducing, neutral, and oxidizing oxyacetylene flames
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. [[File:Bunsen burner flame types.jpg|thumb|Bunsen burner flames with different oxygen levels: 1. diffusion flame, 2. reducing flame, 3. fuel-rich neutral flame, 4. neutral flame]] {{multiple image | align = right | direction = vertical | image1 = OxygenRichBlowTorchFlame.jpg | caption1 = '''Oxygen''' rich butane torch flame | image2 = FuelRichBlowTorchFlame.jpg | caption2 = '''Fuel''' rich butane torch flame }}
==Oxidizing flame== If 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.<ref name="oppi">[https://books.google.com/books?id=r81z6oAOIowC&dq=%22oxidizing+flame+is%22&pg=PA413 "The Anatomy of a Flame"], in: "Jewelry concepts and technology", by Oppi Untracht, 1983, {{ISBN|0-385-04185-3}}</ref> 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.<ref name="oppi"/> The same principle is important in firing pottery.
==Reducing flame== A '''reducing flame''' is a flame with insufficient oxygen. It has an opaque yellow or orange color due to incandescent carbon or hydrocarbons<ref name="google">{{cite journal |title=Brass Melting in Gas Furnaces |journal=The Gas Age |date=February 25, 1920 |volume=45 |publisher=Robbins Publishing Company |issn=0096-0780 |page=196 |url=https://books.google.com/books?id=K6vmAAAAMAAJ |access-date=2015-01-01}}</ref> which bind with (or reduce) the oxygen contained in the materials the flame processes.<ref name="oppi"/> 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.<ref>{{cite web |title=Combustion of hydrocarbon fuels - Fuels - Edexcel - GCSE Chemistry (Single Science) Revision - Edexcel |website=BBC Bitesize |language=en-GB |url=https://www.bbc.co.uk/bitesize/guides/zwp32nb/revision/4 |access-date=2025-10-18}}</ref>
===Reducing flames with no carbon=== Reducing 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== *{{section link|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== {{Reflist}}
Category:Fire