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Author: Subject: Poor alcohol lamp performance
Biochemscientist
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[*] posted on 20-8-2011 at 20:27
Poor alcohol lamp performance


What are some possible causes of (and solutions to) poor alcohol lamp performance?
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IrC
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[*] posted on 20-8-2011 at 22:59


Improperly trimmed wick.




"Science is the belief in the ignorance of the experts" Richard Feynman
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Endimion17
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[*] posted on 21-8-2011 at 07:58


Bottle neck compressing the wick too much because the wick is too thick: cut the wick to make it narrower.
Insufficient amount of wick laying in the alcohol: get a longer wick or insert more alcohol.
Old alcohol with too much water and acetic acid in it: replacee the alcohol.
And, as IrC said - wick that hasn't been trimmed as it should. Trim the wick.

Alcohol lamps can be bitchy. There can be an explosive alcohol-air mixture above the alcohol which can ignite if the lamp is tilted or the wick holder is elevated. It can be cool or not cool at all, depending on the case.




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Mr. Wizard
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[*] posted on 21-8-2011 at 13:47


A compressed wick was my first thought. How does this happen? Somebody buys a new wick and forces it into the slot, and it is too tight. Another problem could be the material of the wick. If it is a synthetic cloth like polyester it will melt at the end forming an impervious bead that won't allow vapor to be emitted. Cotton cloth makes the best wicks. Another problem could be contaminated or watered down alcohol. I have used the 70% ethanol 30% water variety in my youth, but pure denatured alcohol is better. Has the alcohol lamp been sitting with the cap off for a while? The alcohol may have evaporated leaving water behind. Try putting some in a metal container such as aluminum foil, or the bottom of an aluminum soda can. Light the alcohol, and see if it all burn away cleanly. If it leaves a puddle of liquid that won't burn away with a clear blue flame it's too wet with water.

[Edited on 21-8-2011 by Mr. Wizard]
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Melgar
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[*] posted on 21-8-2011 at 21:22


I've made lots of alcohol lamps over the years, and it's sort of a hobby of mine. One thing that has to be there is some gap that allows the air inside and outside the lamp to equalize in pressure. If that gap isn't there, then when you light the lamp, the air inside it will heat up and expand. This will increase the pressure inside the lamp, which will push fuel out of the wick and make a puddle around its base. The puddle will then catch fire and the air inside the lamp will heat up even more, causing a nasty fire.

Water in the alcohol doesn't really hinder its performace much, and I've deliberately added water to the alcohol fuel in order to cool the flame. However, when you go to light it, the alcohol will have evaporated faster than the water, so the wick will be wet with mostly water. So you have to pinch a few drops of liquid out of the wick before you can light it. Even if you're using pure alcohol, you can have this problem, since water will condense on the wick from the air.

Methanol has the coolest flame, then ethanol, then isopropanol. But isopropanol can produce soot whereas the other two won't.

You can give your lamp a cool green flame by mixing a little boric acid in with the alcohol.

Wicks should be either cotton or paper, so made of cellulose anyway. They should be cut significantly deeper than the lamp jar, so that as the wick chars, you'll have enough extra to pull up a little more.
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bobm4360
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[*] posted on 21-8-2011 at 22:09


Interesting series on alcohol lamps here - http://www.modernmicroscopy.com/main.asp?article=78&page...

Regards,
Bob
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