[Cob] roman cement

[Quinn]

Wood ash will create lye in a mix with water.  It usually takes several hours or more for this to happen, but I would assume it is a very caustic substance from the git-go.  Not something I'd want to spend hours slopping around in.

Volcanic ash, like fired clay, is an inert yet minutely porous material, a result of rock/ minerals being burned as opposed to something organic like wood.  I would guess that it contributes more of a physical than a chemical presence to the cob.

"Ash" seems to be a term that simply means "the result of something burned" kind of like "powder" means "the result of something being ground up."  You wouldn't want to substitute powdered coffee for talcum powder.  ; )

happy cobbing,
Quinn
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i would like to ask if hardwood ash (almost exclusively red oak) could be used inplace of volcanic ash to make a mortar. cobbing in pa  chris