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Author: Subject: Getting a clean alcohol flame
bob800
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[*] posted on 17-10-2010 at 15:13
Getting a clean alcohol flame


For a while now I've been trying to get my alcohol burner flame that clear blue color, but there's always a fiery orange layer surrounding the nice blue flame. I'm using ordinary denatured alcohol from the hardware store, which appears to be completely clear without any dyes or additives except 5% methanol. I've tried re-positioning the wick and even tried a different burner entirely, but I just can't get a stable blue flame. Does anyone have any ideas\suggestions?
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psychokinetic
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[*] posted on 17-10-2010 at 15:46


If using a wick, there will always be a bit of orange I think.



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bob800
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[*] posted on 17-10-2010 at 16:13


Quote: Originally posted by psychokinetic  
If using a wick, there will always be a bit of orange I think.


Really? It's not just the little white spot at the top, it's a very noticeable orange ring. Here's a photograph I found on woelen's chemistry website of my exact same burner with a clean flame:


flash1.jpg - 38kB

Maybe I need to trim the wick flatter?
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[*] posted on 17-10-2010 at 17:36


Oh I see, so you're getting orange around the base, too? A flat wick indeed might help that. I don't use lamps like these for chemistry bear in mind - but I've used them on and off for burning aromatherapy oils.



“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found the object of his search.
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FrankMartin
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[*] posted on 19-10-2010 at 16:19


We used to mix a little water with the alcohol to produce a clear blue flame. Do some tests in a small open container (such as metal bottle cap) and add small increasing amounts of water to the alcohol and test the burning after each addition.
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bob800
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[*] posted on 19-10-2010 at 16:34


Quote: Originally posted by FrankMartin  
We used to mix a little water with the alcohol to produce a clear blue flame. Do some tests in a small open container (such as metal bottle cap) and add small increasing amounts of water to the alcohol and test the burning after each addition.


Are you sure that'd help an orange glow around the flame? I think that would eliminate the little white spot at the top, but not the orange (which I think is wick-related).
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[*] posted on 19-10-2010 at 16:48


Have you tried burning it alone in a shallow dish? That would conclusively resolve whether it is your wick or your fuel at fault.



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bob800
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[*] posted on 19-10-2010 at 16:53


Quote: Originally posted by madscientist  
Have you tried burning it alone in a shallow dish? That would conclusively resolve whether it is your wick or your fuel at fault.


Yes, I have, and did indeed get a clean blue flame without any orange. So I guess the wick is the problem, however even with just a little wick I still get an unstable (flickering) orange flame. After running it for a few minutes, the orange isn't terrible, but it still keeps flickering.
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[*] posted on 20-10-2010 at 09:06


I did nothing special with my burner, nor the wick, it always gives a stable flame with a little orange spot near the tip of the flame. I use denatured alcohol with a fuel concentration somewhere around 90%, the rest being water.



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[*] posted on 26-10-2010 at 21:09


Our spirit lamp has a ground-glass cover to keep moisture and rubbish away from the wick when not being used. Alcohol is very hygroscopic. Also a damp unlit wick can retain al sorts of junk from the air. Put something over the wick when the lamp is out; perhaps a pasteur-pipette rubber, or the like.
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[*] posted on 28-10-2010 at 08:47


You could try replacing the wicks with something porous that won't burn. Like capillary tubes, a bit of broken thermometer, glass frit or something else similar. Would chalk work perhaps?

Never tried it so can't say for sure if it works. It should in theory, that's how the fibrous wick is working. Just suggesting it in case you want to do some experimenting.

Failing that, I have used propane torches for heating quite a few things. Those can be adjusted to a very low (almost out) blue flame and then playing with the position or height of the glass over it can produce great temperature control.

When using flames, I tend to also wrap a little foil skirt around the glass and get it close to the flame, or have it inside the skirt, so air currents from doors opening and closing or open windows doesn't blow the flame around.

Rather than a huge soldering / brazing torch, you can use those little ones that were all the rage for a few months for the kitchen, the kind used to caramelize sugar on top of creme broulees and little else.

That's basically a cute bunsen with an ignitor and gas supply all built into one thing. If it's turned down to warm as opposed to burn, it should last a decent amount of time.

Ironically, they'd probably be better for what you're doing, whereas they're not that good for cooking. It takes FOREVER to do one creme broulee and it always ends up with burnt spots and then patches where it hasn't worked. A big blow torch works better for desserts.

Best to work on not making a scrambled egg dessert prior to using gas soldering equipment on the top; creme broulee has a very large amount of egg yolk in it, and will scramble if heated too hard.

[Edited on 28-10-2010 by peach]




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