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Science question. What makes fire start with a flare?
04/09/2012 | self

Posted on 04/09/2012 2:13:42 PM PDT by Lady Lucky

I've been asked one of those questions so basic that you never know 'til you're asked, that you really don't know. So I tried answers.com and all those other reasonable places and still can't answer. I figure there are enough smart people on FR to improve my chances. Question: When a fire starts, why does it flare up with a sudden burst of energy that is more intense than the subsequent flames? What's going on there? Why does it not kindle gradually, appear first feeble and then grow to its regular intensity?


TOPICS: Science
KEYWORDS: fire
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Anybody?
1 posted on 04/09/2012 2:13:55 PM PDT by Lady Lucky
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To: Lady Lucky

It has to do with the quantity of combustable fuel available. Many fuels are more combustable when they are hot and are off-gassing. However, while these are more common in modern usage, they are not the typical case.

Try lighting a candle ... no huge flare. Light leaves, an old oil lantern, paper, charcoal with wooden matches.

If you have an explosive mixture of fuel (propane BBQ grill, lighter fluid, phospohorus - well, then things are a little more interesting, aren’t they?


2 posted on 04/09/2012 2:17:35 PM PDT by Hodar ( Who needs laws; when this FEELS so right?)
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To: Lady Lucky

Magic.


3 posted on 04/09/2012 2:17:49 PM PDT by freedumb2003 ('RETRO' Abortions = performed on 84th trimester individuals who think killing babies is a "right.")
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To: Lady Lucky

Initially, it’s a hot physical attraction. And then you get to know each other.

In movies, it can happen the other way. You know, the friends first thingy. You’ve known each other for years, suddenly, and one day a general warmth progresses into a slow smolder and eventually flames.


4 posted on 04/09/2012 2:18:17 PM PDT by DannyTN
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To: Lady Lucky

Fuel, heat and oxygen makes fire. My guess is the flare up is the oxygen being sucked in towards the heat and fuel. And as I said, it’s a guess.


5 posted on 04/09/2012 2:18:26 PM PDT by Terry Mross ("It happened. And we let it happen." - Peter Griffin, Family Guy)
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To: Lady Lucky
the fire god says "ASK YE NOT OF THE MYSTERIES OF MY REALM"


6 posted on 04/09/2012 2:18:42 PM PDT by Mr. K (If Romney wins the primary, I am writing-in PALIN)
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To: Lady Lucky
Oxygen reacting to Accelerant.
7 posted on 04/09/2012 2:19:03 PM PDT by poobear
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To: Lady Lucky

Thats a very interesting question..hmmm. Thats my usual response when I do not have a clue.
Pure guess does it have something to do with oxygen? I mean there is more oxygen available initially...?


8 posted on 04/09/2012 2:19:33 PM PDT by Leep (Enemy of the Statist)
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To: freedumb2003
Magic

Well yeah, it's ALL magic. :)

9 posted on 04/09/2012 2:19:57 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: Terry Mross

Throw a few gallons of diesel on there and get the party started!!!!!
(do not play with gasoline)


10 posted on 04/09/2012 2:19:57 PM PDT by 9422WMR (Life is not fair, just deal with it.)
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To: Lady Lucky

My guess: the heat needed/used to start the fire, whether friction or another flame, volatilizes some part of the fuel that you are trying to light. This will be invisible/vapor but when some part of it starts to burn, the rest “flashes”.


11 posted on 04/09/2012 2:20:31 PM PDT by FairWitness (Everything is easy, once you've done it once)
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To: Lady Lucky

There is maker recognition that the flare might have to start in a windy or cold environment, so the initial fuel contains extra factors to quickly establish a proper operation temperature for those environments —the rest of the stick will already be somewhat pre-warmed and therefore doesn’t have the need for the extra chemical factors.

That’s a guess.


12 posted on 04/09/2012 2:20:40 PM PDT by gaijin
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To: Lady Lucky

There is maker recognition that the flare might have to start in a windy or cold environment, so the initial fuel contains extra factors to quickly establish a proper operation temperature for those environments —the rest of the stick will already be somewhat pre-warmed and therefore doesn’t have the need for the extra chemical factors.

That’s a guess.


13 posted on 04/09/2012 2:20:57 PM PDT by gaijin
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To: Lady Lucky

It has been years since my last chemistry class so some of the details may be wrong but here goes:

Wood, for example, out-gasses when it is heated. As the wood heats up, it releases flammable gasses. The fire you see is actually the gasses burning, not the wood.

Most flammable things are like this. The oxygen in the air is too diluted to have the combustion you are talking about so it takes the object you are trying to burn the need to ‘heat’ up to cause combustion.

Some chemical reactions, however, work much faster. Put some potassium in water, for example, and you have a fast chemical reaction of the potassium grabbing the oxygen’s extra electron then splitting the bond so the hydrogen atom is released which is highly flammable.


14 posted on 04/09/2012 2:20:57 PM PDT by mnehring
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To: Lady Lucky

It could have something to do with more still air, containing about 20% oxygen, surrounding the initial flare. Just my guess. It could be the rush of oxygen that is needed for fire.


15 posted on 04/09/2012 2:23:38 PM PDT by BatGuano (You don't think I'd go into combat with loose change in my pocket, do ya?)
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To: Lady Lucky

It could have something to do with more still air, containing about 20% oxygen, surrounding the initial flare. Just my guess. It could be the rush of oxygen that is needed for fire.


16 posted on 04/09/2012 2:24:06 PM PDT by BatGuano (You don't think I'd go into combat with loose change in my pocket, do ya?)
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To: Lady Lucky

Actually it has strangely to do with globular warming. When all the little bits come to temperance there is an understanding between them all to get the job done before quitting time aka flash point. So they arrange plans in committee in order to be more effective in their combustible relationships and therefore the end reslut.


17 posted on 04/09/2012 2:24:39 PM PDT by steveo
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To: Lady Lucky
It depends on the availability of temperature, oxygen and fuel at the time of ignition. In the case of the pyrolysis of wood, the flammable gases coming off the heated wood might flare then when the fire stabilizes, goes back to a more steady rate of continued ignition.

In other cases, if there is an available inrush of oxygen when the fire first starts like opening a door or window, then the oxygen flow stabilizes.

In the case of self-ignition, like rotting grass/weeds/oily rags, there is not real flare but a gradual warming, then a flame starts.

The study of fire is really neat and centers around 4 major issues: available oxygen, available fuel, temperature, and ability for a pyrolitic chain reaction to allow for the oxidation of the available fuels. Knock out any one of the 4 items and the fire goes out. So, fire suppression centers on cooling, removing or smothering fuel, reducing temperature, or somehow interupting the chain reaction at the molecular level.

18 posted on 04/09/2012 2:25:10 PM PDT by SERKIT ("Blazing Saddles" explains it all.......)
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To: Lady Lucky

When you start a fire, the maximum surface area of the combustible material is exposed to the oxygen. After a time the burned material acts as a insulator between the oxygen in the air and the fuel. That is why a log fire needs to be stirred and prodded - to knock off the ash and carbon on the outside to expose the unburned wood.


19 posted on 04/09/2012 2:26:36 PM PDT by Feynman
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To: Lady Lucky

Fumes from all that gasoline.


20 posted on 04/09/2012 2:28:39 PM PDT by count-your-change (You don't have to be brilliant, not being stupid is enough.)
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To: Lady Lucky
Mirrors, magic and a littlr Luck, Lady.

/8^)

21 posted on 04/09/2012 2:29:16 PM PDT by knarf (I say things that are true ... I have no proof ... but they're true)
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To: Lady Lucky
Most material catches fire gradually, heating up, and then charring and emitting flammable gas and smoke. The flare up occurs when that hot gas, smoke, and air ignites into flame.

The same process is responsible for the dangerous "flash over" that happens in house fires. Once enough hot gas, smoke, and air has accumulated, it suddenly ignites and the fire spreads rapidly.

22 posted on 04/09/2012 2:30:22 PM PDT by Rockingham
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To: Lady Lucky

A number of variables come into play I suppose. Dryness, water content, wind; other combustible substances, like say, pine sap that might contribute. Ever burn a dried out Christmas tree? Those suckers really burn.


23 posted on 04/09/2012 2:31:11 PM PDT by AFreeBird
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To: Lady Lucky

Any ‘flaring’ would be the result of an abundance of oxygen which would wane to a constant level after the fire is established. I’m guessing. I don’t know squat about physics.


24 posted on 04/09/2012 2:31:45 PM PDT by FedsRStealingOurCountryFromUs
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To: Hodar
It has to do with the quantity of combustable fuel available.

Ok but given a presumably abundant quantity of combustible fuel that feeds the "excess" -- that is, the flare -- what was this quantity doing in the previous second? Why did it not ignite exactly when it was at the quantity, or the density, that feeds the later even flames? Why is it lying there waiting to feed a flare?

Would you say that the heat that is released when the fire ignites, reaches out to acquire more oxygen than subsequent flames have available? Or is something else going on?

It's curious that the change of state from non-fire to fire is explosive rather than gradual -- and yet it's gradual just before it actually combusts.

25 posted on 04/09/2012 2:31:53 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: Lady Lucky

Initially you have to heat whatever you are burning to a gas that is at or above it’s flash point. This process generates a lot of combustible vapor that isn’t quite at the flash point yet. Once the fire starts and flares (burns up the excess vapor) it will die back to the point where it consumes the vapor as it is generated while not allowing an excess to build up like it did before the flare.


26 posted on 04/09/2012 2:33:05 PM PDT by BuffaloJack (End Obama's War On Freedom.)
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To: Lady Lucky

A fire doesn’t have to start with a flare. But two gases are in the equation and their abundance and ratios affect the intensity of the burning.

One is oxygen, or an oxidizing gas (chlorine is another oxidizer). The other gas is the fuel. With the exception of metal, just about any flaming fire is a gas that is burning. This is true of liquid fuel like oil or solid fuel like wood or paper. Prior to ignition, the fuel has to be heated to a point where a flammable gas is evolved. In liquid fuels, this means that the fuel must be at its flash point - the temperature at which flammable vapors are evolved. For gasoline, it is about minus 49 degrees Fahrenheit. For fuel oil (diesel fuel), it is over 100 degrees Fahrenheit. For solid fuels, the heat must be sufficient to pyrolytically decompose the material to a flammable gas. This is why when wood burns, you have a visible flame until it burns down to just the coals. At that point, the material that can be gasified and produce a visible flame is gone, but the remaining carbon is still oxidizing, burning, and giving off heat - just not a flame.

When something is first heated to the ignition temperature, the flammable gases and oxygen are at their maximum abundance. Whatever external heat source is applied to the fuel is causing it to give off gases that ignite when they hit the ignition temperature for that particular fuel. These gases ignite and burn rapidly. If this ignition stage fire produces enough heat to then cause the fuel to continue to give off flammable gas, the combustion is self-sustaining. If it is not, the fire will go out. Usually with solid fuel fires, combustion starts slowly and gradually increases as the the fuel temperature increases, reaching a vigorous free-burning stage. As the fuel is consumed, the flame dies down and eventually combustion stops as wither the fuel is all consumed, or the fire cannot produce sufficient heat to perpetuate the evolution of flammable gas.

Likewise at the moment of ignition, oxygen is at its maximum. It is consumed in the combustion. If the oxygen is not replaced - if the draft to the fire is restricted, the flame will diminish and maybe go out.


27 posted on 04/09/2012 2:33:53 PM PDT by SargeK
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To: mnehring
"The fire you see is actually the gasses burning, not the wood."

So...if the wood doesn't actually burn, then what is that pile of ash that's left...gas ashes? Also, why is it the wood is no longer there?
28 posted on 04/09/2012 2:35:54 PM PDT by FrankR
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To: Lady Lucky

29 posted on 04/09/2012 2:38:08 PM PDT by struggle (http://killthegovernment.wordpress.com/)
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To: Lady Lucky
Boys and girls:

The secret is surface area.

If you will notice, kindling is small pieces of fuel with lots of surface area. Lots of flame, but it doesn't last long. The main fuel, (logs) has the burning distributed over a large surface area, by volume, and, as such, gives off more heat, (burns), over a longer period.

If you're a pyromaniac, it's simple.

30 posted on 04/09/2012 2:38:51 PM PDT by jonascord (Ask any Democrat. He's firmly convinced that he's brighter than you.)
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To: DannyTN
In movies, it can happen the other way. You know, the friends first thingy. You’ve known each other for years, suddenly, and one day

"A brother or a sister, but then the passion flares again...
I wanna hold ya 'til I die..."

31 posted on 04/09/2012 2:39:06 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: Lady Lucky

Gotta another for you...

Science question. What makes water ice melt?


32 posted on 04/09/2012 2:40:09 PM PDT by Jack Hydrazine (It's the end of the world as we know it and I feel fine!)
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To: Mr. K

Well. What would you pyromaniacs like to do first? ;)


33 posted on 04/09/2012 2:40:16 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: Jack Hydrazine
What makes water ice melt?

Heat.

34 posted on 04/09/2012 2:46:25 PM PDT by thackney (life is fragile, handle with prayer)
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To: FrankR

The remaining carbon after the gasses burn off or broken down and ‘went up in smoke’.
http://www.arboristsite.com/firewood-heating-wood-burning-equipment/160520.htm


35 posted on 04/09/2012 2:46:46 PM PDT by mnehring
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To: Feynman; All

Surface area. Hmm. That seems plausible....I think...but if so, then in the instant afterwards, the surface area burning is diminished, whereas you’d expect it to grow. I mean, if the flare diminishes, then the surface area burning also did.
Eh?

Many thanks to everyone, you are ALL Feynmans to me. :)


36 posted on 04/09/2012 2:50:16 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: thackney
Oh yeah?

Well,. why does the shower curtain come into the tub/stall when you're showerin', smarty pants?

37 posted on 04/09/2012 2:51:15 PM PDT by knarf (I say things that are true ... I have no proof ... but they're true)
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To: Terry Mross; lady_luck

my guess as well, maybe because before the flare up the Oxygen available is normal, after the initial flare the air is heated and surrounding air would be less dense, so less Oxygen would be available. Not being a scientist, I really wouldn’t know, they probably don’t either, but I bet they could fill a book or two on the subject anyway.


38 posted on 04/09/2012 2:52:50 PM PDT by itsahoot (Tag lines are a waste of bandwidth, as are most of my comments.)
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To: Feynman
After a time the burned material acts as a insulator

Oh wait. I think I'm getting it now. Virtually immediate cooldown?

39 posted on 04/09/2012 2:55:06 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: Lady Lucky

Sometimes you need more flare...............

40 posted on 04/09/2012 2:56:54 PM PDT by Red Badger (Think logically. Act normally.................)
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To: SargeK
Likewise at the moment of ignition, oxygen is at its maximum. It is consumed in the combustion. If the oxygen is not replaced - if the draft to the fire is restricted, the flame will diminish and maybe go out.

Then, typically, fires exist in a state of increasing starvation? If the oxygen around a fire were to be deliberately added at a steady rate, the fire would continue to flare?

41 posted on 04/09/2012 3:01:27 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: Mr. K

I can be like that for three days out of every month.


42 posted on 04/09/2012 3:11:20 PM PDT by MeganC (No way in Hell am I voting for Mitt Romney. Not now, not ever. Deal with it.)
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To: AFreeBird
Ever burn a dried out Christmas tree? Those suckers really burn.

And hair. It's remarkable, yes.

43 posted on 04/09/2012 3:15:23 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: thackney

Pressure also. On a cake of ice hang weights on both ends of wire and suspend the wire on the cake of ice. The scientific explanation is that ice expands upon freezing and the weighted wire applies enough pressure to reverse the freezing.


44 posted on 04/09/2012 3:20:01 PM PDT by monocle
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To: Lady Lucky
I think it has to do with what you are burning. (E.g. when you strike a match, first you burn whatever it is that is on the tip of the match, and then you are burning paper or wood.) It may also have to the initial flame reducing the density of ambient oxygen in the vicinity of the flame.

ML/NJ

45 posted on 04/09/2012 3:20:41 PM PDT by ml/nj
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To: BuffaloJack
It's that "flash point" that's intriguing.

Basically, though, I'm concluding that even though fire may spread, it is really dying -- fortunately. Nascentes morimur, so to speak: "from the moment we're born we begin to die."

46 posted on 04/09/2012 3:21:48 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: Lady Lucky

It’s called a match head.


47 posted on 04/09/2012 3:23:39 PM PDT by DigitalVideoDude (It's amazing what you can accomplish when you don't care who gets the credit. -Ronald Reagan)
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To: itsahoot
Not being a scientist, I really wouldn’t know, they probably don’t either, but I bet they could fill a book or two on the subject anyway.

Pay your taxes and do not mock the rightful recipients of your tribute!

48 posted on 04/09/2012 3:28:23 PM PDT by Lady Lucky (Romney, the pink slime of presidential politics.)
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To: Lady Lucky

Depends upon the ‘fire’ you are referring to, but let’s say you are referring to a common match.

What you see initially is an accelerant being ignited and burned quickly. When the fuel is gone, the cardboard of the match continues to burn, but at an even rate of combustion, since there is no accelerant.

To watch how most fire burns, minus the accelerant, take a common cotton rag, and then use a magnifying glass to get it to burn. Make sure it’s clean first. You’ll find it smolders, and then you have to blow on it in order for it to turn from an ember to a flame.


49 posted on 04/09/2012 3:28:54 PM PDT by RinaseaofDs (Does beheading qualify as 'breaking my back', in the Jeffersonian sense of the expression?)
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To: FairWitness

Most times if it hasn’t burned, you will light it so that a big gas bubble doesn’t form that could be a real problem.


50 posted on 04/09/2012 3:29:48 PM PDT by richardtavor
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