Allan Cobb said:
>I was up at the Birthday Passage in Palmito once when someone lit a magnesium
>flare in the Hall of Giants. Spectacular does not even begin to describe it.
>It lit up the entire cave!
That may well have been me. :-) I used to take homemade flares to light
up very large rooms like that, or to drop down deep pits. Gave a nice view all
the way down. My flares were based on aluminum, though, not magnesium.
Lyndon Tiu said:
>I wonder what the flare smoke contains? Carcinogens, CO2, CO, Ozone, etc ?
That would depend on the flare, of course. Typical photographic flares
were sometimes just magnesium ribbon (which is undoubtedly what Keith Goggin
meant, not manganese). When that burns it gives off only magnesium oxide.
While I wouldn't want to breathe it, it probably isn't particularly harmful.
It would slowly react with carbon dioxide from the air and turn into magnesium
carbonate, a component of dolomite, which some caves are formed in. Other
photo flares were thermite, which is a mixture of aluminum powder and iron
oxide. It gives off molten iron and aluminum oxide, again probably not
terribly bad as long as you don't breathe it. My flares were aluminum powder,
barium nitrate, and a little sulfur to bind it all together. The sulfur would
produce sulfur dioxide, which is definitely not good, although it was a minor
component of the mixture. Common road safety flares probably have much less
agressive chemicals in them, because they are meant to burn for a long time
rather than being incredibly bright. Who knows what's in them, but probably
organic compounds that you wouldn't want to breathe.
In general, I agree with Jim Kennedy - don't do it. It was long ago
when I made flares, and no one thought much about the environmental
consequences. It was definitely not caving softly.
Mark Minton
Chemist
