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Ash or ashes are non-volatile solid residues that remain after a material is burned. In analytical chemistry, in order to analyze the mineral and metal content of chemical samples, ash is the non-gaseous, non-liquid residue after a complete combustion.

Description and properties

Ash, as the end product of incomplete combustion will be mostly mineral, but usually still contain an amount of combustible organic or other oxidizable residues. Typical ash is usually gray in color. The darker the wood ashes are, the higher the content of carbon will be present due to incomplete combustion.

Since ash is strongly alkaline, it will react with acids, releasing carbon dioxide.

Types of ash:

  • Wood ash: It is the residue powder left after the combustion of wood and wood-related items, such as burning wood in a home fireplace or a kiln. It is used traditionally by gardeners as a good source of potash.
  • Coal ash: The residue obtained from burning coal, classified as: bottom ash (the non-combustible residue of combustion in a power plant), fly ash (fine particles of burned fuel that are driven out of coal-fired boilers together with the flue gases), breeze (ash recovered from burning urban rubbish).
  • Cigar ash: The ash produced when a cigar is smoked.
  • Incinerator bottom ash: A form of ash produced in incinerators.
  • Cremains: Ashes and dried bone fragments left from cremation.
  • Volcanic ash: Ash that consists of glass, rock, and other minerals that appears during an eruption.


Ash can be found in many places.

DIY ash

Ash can be made by burning wood, coal or some other organic material. The more oxidizing the atmosphere in the kiln is, the lighter in color the ash becomes.


  • Make KOH
  • Make soap
  • Make ceramic glazes
  • Garden fertilizer

Handling and safety

Ash is highly alkaline, and contact with unprotected hand may cause irritation or eczema.

Coal ash contains heavy metals and phenolic byproducts, many carcinogenic.

Volcanic ash is extremely abrasive and inhalation of said powder will lead to severe lung illnesses.

See also


Relevant Sciencemadness threads