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  1. #61
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    To diverge only slightly and at the risk of inflaming a conflagration, may I propose this answer to a different aspect of the candle question:
    Can a higher melting point affect how long a candle burns?
    When the candle is burned, the wax goes through 3 phases. Solid to liquid to gas. The flame comes from the wax in its gaseous state. But the melting point pertains to the solid to liquid phase change. That phase change happens because the flame radiates heat down to the surface of the candle. The melting point is a factor because the higher the melting point, the smaller the pool of melted wax that is available to be drawn into the wick. A smaller pool of liquid wax means that the edges of candle don't melt as quickly and the bowl will be deeper, AND that the flame will be smaller. That's why a higher melting point wax makes a candle that burns longer - all other factors being equal.
    "Before I speak, I have something I'd like to say. . . . I will try to keep this short as long as I can." Yogi Berra

  2. #62
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    > Can a higher melting point affect how long a
    > candle burns?

    To a tiny and insignificant extent,
    and only at the beginning of the process.

    What's the temperature of a typical
    candle flame? 1400, maybe 1500 F

    What's the melting point of wax?
    Somewhere around 120 - 140 F.

    Go ahead and freeze the candle in
    liquid nitrogen, modify the wax itself,
    add stuff, whatever. You aren't
    going to make it any more difficult
    for that 1500 degree flame to melt
    the wax, and burn the wax.

    The liquid nitrogen freeze (-320 F or
    so) might make the candle hard to light,
    but even then, once you get the wick lit,
    the flame WILL melt the wax, and will
    melt wax much faster than it burns wax.

    Ain't physics fun? [img]smile.gif[/img]

  3. #63
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    Yes, physics IS fun. A candle flame might be 1400-1500 degrees at the tip of the flame, but it's certainly not at the base of the flame. And the temp is even less below the flame where the solid-liquid interface (melting point of 143-148 degrees) is located. If the flame were that hot throughout, the candle would quickly melt completely and would be an oil lamp instead of a candle. There is an amazing temperature gradient within any flame. In point of fact, the unburned wick inside the flame is at the temperature where beeswax changes from liquid to gas - appx. 300 degrees. You can readily test this by bending a glass tube. Light a candle and hold the glass at the base of the flame. It will be hard to bend the glass because you can't get it hot enough. In fact, it will get covered with soot. But hold it at the tip of the flame and the glass quickly becomes red hot and then soft.
    Anyway, the point is that the temperature quoted is not too relevant to the solid-liquid phase change because it is above it an inch or more and moving away (heat rises). The whole process is an amazing balancing act.
    Besides melting temp. you can affect burning time of a candle by varying the wick size. A larger wick holds a larger flame, which melts the wax faster, makes a larger puddle of melted wax, which supports the larger flame. The tip of the flame on this candle will also be many times higher than the liquid-gas point of beeswax, and somewhat higher than the smaller flame of a similar candle with a smaller wick.
    So, back to melting point of the wax affecting burn time. Parrafin candles have a melting point varying from 104 to 160 degrees depending on how much stearin is added. To quote from a candle-making source: http://www.candlewhiz.com/introduction/wax.php
    "Stearin increases the melting point temperature of wax. This in turn is the reason why stearin helps paraffin wax burn slower."
    So, I'm not familiar with whether you can change the melting temp. of beeswax, but if you did, THEN it follows that a candle made from it would certainly burn longer than an equivalent candle made with regular melting point beeswax. And that's all I was trying to say.
    "Before I speak, I have something I'd like to say. . . . I will try to keep this short as long as I can." Yogi Berra

  4. #64
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    > that's all I was trying to say.

    Sorry, thought you were asking a question
    because you wanted an answer, not to try
    to "make a point".

    Yes, the INITIAL melting would be slower,
    so lighting the candle might be difficult,
    but there is little difficulty posed by
    slightly different melting points given
    that the candle won't burn at all until
    you have at least some liquid wax to
    be wicked up the wick, and liquid wax tends
    to melt the solid wax around it, "helping"
    the process along once liquid wax is present.

    > "Stearin increases the melting point temperature
    > of wax. This in turn is the reason why stearin
    > helps paraffin wax burn slower."

    They forgot to add the key word "insignificantly". [img]smile.gif[/img]

    > So, I'm not familiar with whether you can
    > change the melting temp. of beeswax, but if you
    > did, THEN it follows that a candle made from it
    > would certainly burn longer

    OK, do the math yourself, and see:

    You can estimate temperature (T) at a distance
    (r) from the flame, where T(r) follows a
    simplified heat equation in 3D (polar)
    coordinates:

    (1/r^2) D/Dr( K r^2 DT/Dr ) = 0

    Where:

    1) D/Dr is the partial derivative with r

    2) K is the thermal conductivity of air (in meters^2/second).

    3) T(r=0) is flame temp

    4) T at a large r is simply room temperature (25 C or so).

    Integrate twice on r and apply the boundary conditions to solve for T(r).

    The above equation is likely in just about
    every textbook you could find.

    To measure the actual temperature at various
    points on a flame, just point a spectrograph
    at the flame itself through a spotting scope.

    What swamps out what?

    Physics is much less fun when there's
    boring math to do.

  5. #65
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    Ha, almost 3 weeks to the day, I knew you guys couldn't let this post die a forgotten death!

    I'm getting my next batch out of the freezer right now!

  6. #66
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    Post

    I miss Searcher I thought he was onto something.

    I have enough saved up for one snowshoe.
    Bullseye Bill in The Scenic Flint Hills , KS
    www.myspace.com/dukewilliam

  7. #67
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    Jim, why are you being so scratchy to me? I didn't ask a question and I didn't try to "make a point". I proposed an answer to a part of the question, then I tried to clarify it. I only agreed physics is fun after you said it and I never said math was boring. The formula you listed is fine, but not overwhelming. It basically says that heat radiates in a predictable way based on temperature and distance. No question. There isn't a lot of heat involved in a candle flame, though. We're not talking about a roaring fire, here. We're talking about a very small flame radiating only slightly more heat than the mass of the candle can absorb. In those conditions, melting point is not insignificant. Here is another illustration. If you made a candle from a solid with a melting point near room temperature ( say Crisco), you only have a melting point delta of about 50 degrees. Do you think it would behave like a beeswax candle? If you made a candle from a solid with a melting point 50-100 degrees higher than beeswax (say soft plastic), do you think it would behave like a beeswax candle?

    I'd hope there isn't a need to be scratchy about this. It's a pretty low priority question after all.
    "Before I speak, I have something I'd like to say. . . . I will try to keep this short as long as I can." Yogi Berra

  8. #68
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    Thanks for the lucid explanations, TX Ashurst. It is quite refreshing (and, unfortunately, uncommon) to read remarks that are straight forward and to the point. Even I could understand what you were saying. Just my opinion, of course, but often these "debates" are little more than attempts to "win" by offering "scientific thought" which in reality is little more than a mocking attempt to "baffle with bull [feces]". Keep up the good work.

    Note to Bill: I googled 'prednisone'. One of its side effects is increased hair growth. FWIW

  9. #69
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    TX: Your example of a substance with a much
    lower melting point is good, but I guess what
    I can't make clear is the negligible nature of
    variations of less than 100 degrees when compared
    to a flame well over 10 times the melting
    point, no matter how much you want to de-rate it.

    As you mentioned, different wick sizes would
    make a difference, more difference than the
    minor variations in melting points and ignition
    temperatures. The wick would control the
    amount of fuel fed, and thereby make a larger
    flame, burning more wax.

    If you don't want to do the math, that's OK,
    but please don't think that a minor change
    in just the melting point is going to make
    the candle burn longer, given the very
    large delta between any possible melting point
    and the minimum possible flame temp.

    Melting is going to happen "for free", and
    the rate of consumption is going to be
    a property of the basic material, not subject
    to much modification, as ignition temperatures
    of anything that can be burned will be,
    by definition, slightly less than the usual
    temperature of the flame. (I'm ignoring
    purely chemical reactions like magnesium flares
    here, as discussion of super-high temperature
    combustion won't help us to better understand
    candles.)

    Scratchy? No way. Just trying to point out
    that the heat required to create the
    "liquid/solid interface is much higher than
    the resulting temperature of the interface
    itself. Also, if the flame generated only
    slightly more heat than the mass of the candle
    could absorb, then one would be unable to burn
    one's finger by placing it in the air near
    the base of the flame. If you try it, you
    quickly find that there is lots of excess
    heat not being absorbed by the mass of the
    candle available to give you a 3rd degree
    burn.

    Dick is strongly advised to not try the above,
    as he would ignore the evidence of the painful
    burn as mere "scientific thought", and would
    continue to hold his finger there until he
    required medical treatment, which he would
    reject as even more "scientific thought", but
    he'd be unable to dial 911 or drive himself
    to the emergency room due to the rejection of
    the "scientific thought" that went into both
    the internal combustion engine, and the
    telephone system. [img]smile.gif[/img]

  10. #70
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    Jan 2005
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    "Baffle them with BS"

    Now we are mixing physics, math, AND legaleese?

    BubbaBob

  11. #71
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    >Note to Bill: I googled 'prednisone'. One of its side effects is increased hair growth. FWIW

    Good. I'll need the extra fur for my trip into the tundra

    >Jim, why are you being so scratchy to me?

    Don't take it to heart, he gets a feather in his hat for everyone he 'shuts up' or chases off the board. By now he looks like a cockatoo.
    Bullseye Bill in The Scenic Flint Hills , KS
    www.myspace.com/dukewilliam

  12. #72
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    >I'll need the extra fur for my trip into the tundra

    Maybe you could bring some candles with you, too. (and a slide rule to do Jim's calculus.)

    Jim, that last paragraph of yours truly had some humor in it. Honest.

  13. #73
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    I can't make clear is the negligible nature of
    variations of less than 100 degrees when compared
    to a flame well over 10 times the melting
    point, no matter how much you want to de-rate it.


    http://www.duess.com/publish/archive...your_darli.php

  14. #74
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    May 2005
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    Dick, I've read King's book on writing and it was good on several levels. You make a good, subtle point above.

    Thanks.
    "Before I speak, I have something I'd like to say. . . . I will try to keep this short as long as I can." Yogi Berra

  15. #75
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    Mar 2003
    Location
    Mobile, Alabama
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    TX Ashurst,

    Thanks for the info - easy to read and understand.

    Things will only remain scratchy so long as you disagree with HIM...

    I once admitted that I enjoyed ABJ more than Bee Culture magazine in response to a query by a forum member (HE writes for Bee Culture). Oops! Scratchy, scratchy! Apparently that type of discourse is not permitted here, but HE promptly pointed out how stupid I was and the situation was rectified.
    Rob Koss

  16. #76
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    Bill, sometimes your wisecracks are very insightful, and I'm not speaking about wearing fur on the tundra.

  17. #77
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    Sep 2004
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    Double, double toil and trouble; / Fire burn, and cauldron bubble

    Out, out, brief candle!

  18. #78
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    Oct 2002
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    The Scenic Flint Hills , KS
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    Perhaps the exorcism worked? Is this a calm peace I feel? Can it last? We'll see.
    Bullseye Bill in The Scenic Flint Hills , KS
    www.myspace.com/dukewilliam

  19. #79
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    May 2005
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    Blessed is the peacemaker.
    "Before I speak, I have something I'd like to say. . . . I will try to keep this short as long as I can." Yogi Berra

  20. #80
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    > Blessed is the peacemaker.

    I dunno, while the peacemaker was Colt's most
    popular revolver, I think that just about any
    9mm automatic would be more likely to be
    "blessed", in the "held in veneration" sense. [img]smile.gif[/img]

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