Vintage light mantles

Discussion in 'Fettling Forum' started by Alex74, Feb 21, 2020.

  1. MYN

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    Alex, if you use clay, lime or any other refractory powder, keep the amount as small as possible. Just a slight but uniformly distributed addition would perform. Just the slightest smear possible. If its heavy, the light would dim too much.
    I've replaced the earlier mantle with a different composition: predominatly lime and a very small percentage of chromic oxide. Its now slightly brighter with a golden yellow hue. Now its the only pressure lamp I've known to produce such a strongly yellow light. My phone camera couldn't capture the real colour but the white wall background was rendered completely yellow:
    20200315_233419.jpg
     
  2. MYN

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    I'll add that its quite safe to say that anything that would melt under a propane-air torch wouldn't work. I've even tried silica fume. The fine particles melted in the flame within the mantle, fluxing and lowering the melting temperature of the original mantle materials, causing holes to form quickly.
    I'd suggest some cheap, common and easily available materials such as calcium, aluminium and magnesium oxides to start with. You need not obtain these from special chemical suppliers.
    I don't think I'd be able to push much further the candoluminescent limits of thorium dioxide and make it glow blueish-white. I've actually tested before, a thoriated mantle with the hottest oxidizing flame from an oxy-acetylene torch. It didn't attain anything near the blue-white spectrum. Instead, it merely glowed just a little whiter and brighter than what could be achieved in a lantern, before eventually melting(that was probably a little over 3300 degC).
     
  3. Alex74

    Alex74 United Kingdom Subscriber

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    Myn,

    just saw your replies and the latest photo. that looks fabulous. If the effect is permanent on the mantle then I’d say that you have succeeded in the quest for a warmer light, so it was well me starting this thread, as I don’t think the topic was ever discussed on here. I haven’t had time to buy powder oxides to experiment with yet, because of work and other commitments. This blooming virus isn't helping either! But I’ll certainly look into it and post a few photos soon. In the meantime, if you manage to improve the light output further, then let us know how you did it!
     
  4. MYN

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    @Alex74
    Yes, I've managed to refine it a little. The key is, you'd need to incorporate the bare minimum of additional oxides into the existing mantle to give the best outcome.
    The oxides need to be in the finest form available(fine enough to stain anything its rubbed on, just like the way soot does).
    In my case, I've used kerosene as a wetting medium for chromic oxide. Any excess oxides must be removed as much as possible and once the kero dries up, the mantle's ready and should be uniformly stained a pale green or any other colour of the oxides used. This is to ensure it doesn't mask out the light by creating dark spots when the mantle's glowing.
    I've tried it on a thoriated mantle(which if untreated, would glow a greenish white).
    Now it glows clearly a bright yellow, which is very similar to that produced by the low pressure sodium lamps. I'd say that no manufacturer would deliberately produce mantles which emit this sort of strong yellow.
     
  5. Alex74

    Alex74 United Kingdom Subscriber

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    No, they probably wouldn’t, but maybe here we have identified an emerging market niche. Mantles that give off light for various moods and occasions. A reddish one for a romantic dinner, a yellowish one for a foggy night etc. The one colour we’ll never likely achieve with glowing oxides is blue, of course as Grey body radiation and the candoluminescent emission line would swamp the 400 nm region I imagine.
     
  6. MYN

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    The blues and violet ranges are not likely to be achievable by merely heating the oxides or any other materials to incandescence. Well, the statement holds true if we're limited to what temperatures are attainable by burning common hydrocarbon fuels in air. As for the additional candoluminescent effect, I don't think there are any new discoveries with materials that'll exceed the short wavelength limits offered by thoria and other known rare earth oxides.
    In my knowledge, if we're to get to the blue range by heating, that'll require temperatures above 6000K, which would be hotter than the Sun's surface, where any known material would have melted or vaporized.
    However, there's one that produces a blue-white flame, and even some ultraviolet.
    That's burning magnesium in pure oxygen.
    But I doubt if that is even close to 6000K. There's something about the light of burning of magnesium besides blackbody radiation.
     
  7. Alex74

    Alex74 United Kingdom Subscriber

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    MYN,

    yes, Mg in pure oxygen is pretty fierce, and probably not that good to look at, given UV comes out of that flame. We’ll have to remain content with shades of yellow and orange for our ‘mood enhancing’ (romantic) mantles!....or just paint the glass yellow, as you’ve done before!
     
  8. MYN

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    I've not painted the glass yellow, Alex.
    Well the yellows are somewhat 'romantic' in some ways. The oxides I've added earlier somehow reduced the candoluminescent effects of the original mantle while shifting the output a little more towards purely blackbody radiation at whatever temperature it was glowing with.
     
  9. Alex74

    Alex74 United Kingdom Subscriber

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    Ahhh ok. I must get hold of some CaO to try. Would CaCO3 extracted from a local quarry work too? Presumably if I pounded it to the finest powder with a mortar and pestle ana applied it to the mantle by ‘wet dispersion’, it would decompose to CaO and CO2 in the flame, right?
     
  10. MYN

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    Limestone(calcium carbonate) might or might not work. Garden lime(calcium hydroxide) would. You'll need more than a mortar and pestle to make it fine enough. A homemade ball mill or something. Perhaps calcine the quarry limestone by heating to red heat would help reduce it to crumbly or fine powder form.
    I won't suggest wetting with water because it'll leach out the original mantle salts and make it useless.
     
  11. george

    george United States Subscriber

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    God knows I'm not a chemist but wouldn't copper give off a green color? Dumb question, I'm sure... sorry guys...
     
  12. MYN

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    Not a dumb question. Copper salts indeed give a green coloration to the flame. But no copper compounds could be sustained as mantle materials without eventually vaporizing off to exhaustion.
     
  13. Alex74

    Alex74 United Kingdom Subscriber

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    MYN,

    you seem to be too knowledgable on everything fire and beyond, for an average Joe. What do you do for a living if I may ask? Industry or academia?
     
  14. MYN

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    What I know is just a little general knowledge, Alex. By the way, I'm in the industry. Basically, electrical by profession.
    But if it is stuffs about fire, I just have a certain 'affinity' to 'mess around' with them since childhood. So whatever I've said here was coincidentally tried and meddled with.:)
     
  15. Alex74

    Alex74 United Kingdom Subscriber

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    :twisted::twisted::twisted::twisted:MYN,

    yeah- I also seem to have a ‘pyromaniac streak’ since early childhood which eventually led to me getting higher degrees in chemistry and ultimately the career I’m in now. But then again, one has to follow his vocation right? :twisted:
     
  16. MYN

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    Haha, I can see that. I kinda like a little chemistry too. Otherwise, it wouldn't had been so coincidental for me to have chromic oxide for the previous mantle trials.(I was using some of it to synthesize the hexavalent and carcinogenic sodium chromate, dichromate and eventually chromic acid):twisted::mrgreen:. Well, nothing to do with lanterns but intended for some corrosion inhibition and some sort of conversion coating experiments.
     
  17. Alex74

    Alex74 United Kingdom Subscriber

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    You’re definitely more :twisted: than me then!!! :twisted::twisted::twisted::mrgreen:
     
  18. MYN

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    Its nice getting to know more pyromaniacs like you. You should be able to get the kind of desired light from the mantle if you really wanted to.
     

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