water wet not sap wet

[openspaceman]

Makes sense to me.. But if you burn it hot you shouldn't have any problems , just a reduction in efficiency. It seems to me it might become an issue when you do a slow burn.

 

First off sap is just water with a few hormones, sugars and electrolytes in it. When it dries these are either lost as vapour or remain in the dried wood, energy wise I suspect they are vanishingly low in their contribution to heat. After the cell contents have dried then there is still some water weakly bonded to the wood fibre. I do not know how water is re absorbed into the wood but logically it wets the surface layers first.

 

You have the nub of it though, water robs heat from the fire in order to vaporise. This lowers the combustion temperature and low combustion temperatures lead to poor combustion and products of incomplete combustion being given off.

 

A slow smouldering burn with no flame is basically just the wood char burning and driving off water vapour and the gaseous pyrolysis products. These are the things that normally burn with a flame but if there is too much water vapour they simply do not burn and exhaust as a white-yellow smoke which may condense out in the flue.