4 ms·

Charcoal has a surface area of a few acres per teaspoon (which makes sense when you look at a micrograph, since all the woody cell walls are preserved https://w

Charcoal has a surface area of a few acres per teaspoon (which makes sense when you look at a micrograph, since all the woody cell walls are preserved https://www.youtube.com/watch?v=kF10i39VQ4w https://www.youtube.com/watch?v=kF10i39VQ4w), whereas carbon fiber composites are impregnated with resin. Obviously all it takes is one oxygen/carbon interface to cause an explosion, as we saw. Similar to explosives, the more thoroughly mixed it is the more energetic the reaction. Pouring LOX over charcoal and soaking charcoal in LOX are very different (the first ignites vigorously, the latter explodes like a stick of dynamite). http://www.popsci.com/diy/article/2009-09/most-dangerous-way-light-grill http://www.popsci.com/diy/article/2009-09/most-dangerous-way...

azernik 10y ago
On a similar note, all kinds of materials that you wouldn't expect become very flammable with high surface area and/or pure oxygen environments. See e.g. the thermal lance, which is a very powerful cutting tool that works by running oxygen over iron (rust at high speed!). Or the very serious risk of explosions in flour mills due to high amounts of dust suspended in the air.
- freehunter 10y ago
  Yup. Growing up on a farm, it wasn't uncommon to hear of explosions in grain silos from a spark in the dust or barn fires from undried hay bales. That's right, wet hay bales can and will spontaneously combust. It sounds counter-intuitive, but wet hay bales are more dangerous than dry hay bales, because hay actually heats up as it dries. As the hay gets hotter, it starts giving off flammable gas. The heat it is generating combined with the gas it is giving off means they could light on fire at any moment if they've been stored before fully drying. And where is hay commonly stored? In a barn, with an attached grain silo. And that grain silo is sometimes full of fine dust. Which, like flour, can easily explode at the smallest spark or flame.
  - slededit 10y ago
    The main ingredient is bacteria feeding on the hay, which causes an exothermic reaction. Above a certain temperature the thermophilic bacteria get happy and a runaway reaction occurs. These bacteria need moisture to survive.
    - schiffern 10y ago
      Essentially you're creating a compost pile unintentionally. This phenomenon is easy to exploit actually. Laying out "sheet mulch" with 9-12" of hay on top of an opaque layer (typically newspaper or cardboard) can greatly accelerate the production rate of soil and repair degraded soils. No tilling or digging required, the mulch retains water and cuts down evaporation, and weeds are smothered by the opaque layer. This yields high quality produce without fertilizer and with a minimum of labor. The late Bill Mollison of permaculture design describes it here (@21m): https://vimeo.com/142711756 https://vimeo.com/142711756
  - Florin_Andrei 10y ago
    Given the volumes involved, the deflagration must be monumental.
    - freehunter 10y ago
      Someone take this man's thesaurus away! :)
      - Florin_Andrei 10y ago
        With apologies. In the interest of public wellbeing, from now on I shall restrict my vocabulary on HNews to Python keywords only.
        nercht12 10y ago
        2.7 ? XD is shot

azernik 10y ago

On a similar note, all kinds of materials that you wouldn't expect become very flammable with high surface area and/or pure oxygen environments. See e.g. the thermal lance, which is a very powerful cutting tool that works by running oxygen over iron (rust at high speed!). Or the very serious risk of explosions in flour mills due to high amounts of dust suspended in the air.

freehunter 10y ago
Yup. Growing up on a farm, it wasn't uncommon to hear of explosions in grain silos from a spark in the dust or barn fires from undried hay bales. That's right, wet hay bales can and will spontaneously combust. It sounds counter-intuitive, but wet hay bales are more dangerous than dry hay bales, because hay actually heats up as it dries. As the hay gets hotter, it starts giving off flammable gas. The heat it is generating combined with the gas it is giving off means they could light on fire at any moment if they've been stored before fully drying. And where is hay commonly stored? In a barn, with an attached grain silo. And that grain silo is sometimes full of fine dust. Which, like flour, can easily explode at the smallest spark or flame.
- slededit 10y ago
  The main ingredient is bacteria feeding on the hay, which causes an exothermic reaction. Above a certain temperature the thermophilic bacteria get happy and a runaway reaction occurs. These bacteria need moisture to survive.
  - schiffern 10y ago
    Essentially you're creating a compost pile unintentionally. This phenomenon is easy to exploit actually. Laying out "sheet mulch" with 9-12" of hay on top of an opaque layer (typically newspaper or cardboard) can greatly accelerate the production rate of soil and repair degraded soils. No tilling or digging required, the mulch retains water and cuts down evaporation, and weeds are smothered by the opaque layer. This yields high quality produce without fertilizer and with a minimum of labor. The late Bill Mollison of permaculture design describes it here (@21m): https://vimeo.com/142711756 https://vimeo.com/142711756
- Florin_Andrei 10y ago
  Given the volumes involved, the deflagration must be monumental.
  - freehunter 10y ago
    Someone take this man's thesaurus away! :)
    - Florin_Andrei 10y ago
      With apologies. In the interest of public wellbeing, from now on I shall restrict my vocabulary on HNews to Python keywords only.
      - nercht12 10y ago
        2.7 ? XD is shot