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What causes the color of ash?

After burning wood charcoal, I found the color of ash varies from light gray to brown, even if the charcoals are from the same wood species.

What chemical compounds that cause the color of ash?

Can we change the color of ash by adding something to charcoal prior to burn?

Thanks in advance.

Update:

To Steve:

So we can say that if the charcoal produces light color ash, it means they burn hotter than dark color ash?

Update 2:

Hi again Steve:

Since major components of ash from charcoal burning consist of:

- Calcium Carbonate (25%-45%), CaCO3, fine white powder

- Potassium Carbonate (less than 10%), K2CO3, white hygroscopic solid.

Unburned carbon lends gray color to ash (black + white = gray).

Meanwhile, under high temperature, then CaCO3 will decompose to CaO (calcium oxide, pale yellow), and K2CO3 will turn to K2O (potassium oxide, pale yellow). Again, unburned carbon lends brown color to ash (black + yellow = brown).

Thus, we can conclude that brownish ash charcoal burns hotter than grayish ash charcoal.

Of course, further robust scientific experiments need to be conducted to confirm this conclusion.

Do you agree with my conclusion?

2 Answers

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  • 1 decade ago
    Favorite Answer

    charcoal ashes can be similar to wood ashes

    http://en.wikipedia.org/wiki/Wood_ash

    "Wood ash contains calcium carbonate as its major component, representing 25[4] or even 45 percent.[5] Less than 10 percent is potash, and less than 1 percent phosphate; there are trace elements of iron, manganese, zinc, copper and some heavy metals.[4] However these numbers vary as combustion temperature is an important variable in determining wood ash composition."

    the difference in color is likely due to differences in combustion temperature..

    not to mention any food drippings

    you can change the color of ash by adding addditional supply of forced air to increase the effectiveness & the temperature of the burn

    the carbonates CaCO3 & K2CO3 (potash), should decompose to CaO & K2O

  • ?
    Lv 4
    5 years ago

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