(If you can't boil a litre of water in a kettle on your stove-top in 10 minutes you need to ask yourself what you are not doing right. Most likely your timber is not dry enough.
Moisture content for any firewood MUST be below 25% and really should be as low as can be got. All felled wood will season naturally (by air drying) unless it is stored in a pond.
Natural seasoning can take many years for timber left to its own devices, but crosscut billets and blocks, well managed, may dry to 15% in less than 12 months and when split will dry even more quickly, depending on storage and the prevailing weather conditions.
I am obliged to Quora for the following which has been tailor-edited by me for this article:-
"A fully grown oak tree can transpire 40,000 gallons of water per year.
Water is used during growth and is absolutely essential for metabolism. H2O is split in to H+ and OH- elements and both are used to manufacture complex organic compounds".
Precisely how much water is thus utilized remains uncertain, but experiments suggest 5% is a reasonable guesstimate and that 95% of the water taken up from the soil passes right through to be transpired into to the atmosphere.
Think about this for a moment. A typical tall tree 100 years old (such as the sycamore felled at Hadrian's wall) will suck up to 100 gallons of water a day for hydration when it matters.
An acre of mature trees (1000) can lift 100,000 gallons of flood water out of the acre in one day while if the acre was in grass or scrub there would be almost none without run-off.
Living trees contain extraordinary amounts of water and the amount varies by variety and the ground under them. Moisture content varies from season to season in standing timber and also between different parts of the tree.
... insert the article about the felled tree and the planted saplings ...
Water evaporates continuously from the tissues of felled timber until the contained water is balanced by the humidity of the surrounding air. It has then reached its Equilibrium Moisture Content. Although EMC is both changeable and variable, 30% is ballpark for the British Isles. Wood above 22%, although it will burn, and is generally dry enough to fire, wastes heat by having to evaporate its contained water and causes boat stoves to give off less radiant heat. The fire burns cooler and emits more smoke. This smoke causes a build-up of creosote in flues and emits solid particulates into the surrounding air.
This matters hugely in canal boats.
Creosotes boil about 230ºC and FLUE temperature should be higher than 120º which in itself is a useful indication as to the minimum temperature for running a stove and how to check it by measuring flue temperature about half way up.
"Heat gradient" means measurements taken at the bottom of the flue will be highest and at the point where thee gases reach the outside air will be lowest.
At this point it is salient to note that charcoal comes with less than 1% contained water and my restaurant grade lump-wood charcoal contains no creosote whatever.
Also my charcoal only burns for a few minutes when first ignited. From them on it glows and this is the real secret of my use of charcoal to heat my boat.
Carbon (from Latin carbo 'coal') is a chemical element; symbol C atomic number 6. It is nonmetallic and tetra-valent.
Freshly felled wood contains considerable and measurable amounts of water calculated as a percentage of the "Oven Dry Weight". Green Moisture Content indicates how dry the timber is at felling and during seasoning. GMC can range between 30% and 200% and between these extremes GMC depends on age when felled, species, growing conditions and the length of a piece of string.
Mature eucalyptus camaldulensis typically returns 45-50% GMC at felling which is MUCH too high for burning.
A WARNING ... (Eucalyptus is not for indoor use; Bark and leaves give off toxic fumes!) ... although properly seasoned it is excellent for outdoor barbies due to the high oil content of the wood, Once the wood moisture content equalizes with its surroundings it will contain about 10-15% water.
Above 25% most woods burn inefficiently, generate smoke and give poor heat. Wood periodically dampened (ie not specifically protected from rain!) dries quicker than wood in a dry environment. Surface dampness keeps cellular pathways open and moisture moves to the surface by osmosis, where it evaporates more easily during dry days. Thus, it dries more quickly and stays dry out in the weather than if stored indoors.
Having said that of course once it is down to ODC it will stay drier inside but only by a tiny margin
ODC Oven Dry Weight indicates totally dry timber such as carpenters and joiners would use. Totally dry timber is deemed to contain no water though this is not always the case and depends on various factors such as species, age, the merchant who sold it before it was fully seasoned and the long-term humidity of its storage point.
It has been determined that a cubic metre of freshly-felled oak contains over half a metric tonne (540L) of water, the water being held in the cellular structure of wood, which is made up of cell cavities and cell walls. 'Free' water is held in the cavities and 'bound' water in the walls.
There is no calorific difference between timber types based only on the Oven Dry Weight. But denser timber burns longer because of its higher calorific density. The only consideration for burning wood is that it should be as dry as possible.
If a tree is felled in winter, MINIMUM moisture content will be over 50% and, if felled in summer figures like 200% have been recorded for the wettest species. 'Wettest' coincides with types found by rivers and canals: poplars, willows, alders, but surprisingly not ash.
By splitting logs and/or cutting them to short lengths, drying rate is accelerated. But it is still going to take many months rather than few weeks. Cutting in winter when the sap has dropped into the roots is a good idea. The reason wood needs drying out is that when you put a log into a fire all the moisture must be driven off before the wood will burn and it must use heat from the fire to drive out all the moisture. Sometimes it uses ALL the heat!
But there's a further problem
Wet/damp/moist wood will not burn cleanly. It will pollute the air with "solid particulates" and deposit corrosive tar in the flue creating future fire risk if the user later learns how to max the heat.
How dry the wood needs to be to burn well will vary from stove to stove, but the highest moisture content should be less than 30%. 20% is acceptable. 15% is ideal. Drying to 30% usually happens within a year, 20% within two years and in ideal conditions those times may be halved. How long it takes dry depends on how the wood is dealt with. Ideally it should be split as soon as possible, stored off the ground outside in a place where air can circulate through and stacked to avoid water-logging. Vertical is good.
SPECIFIC CHARACTERISTICS OF TIMBERS
APPLE: Splendid. burns slowly and steadily when well seasoned, with little flame, but good heat. malus genera are all good
ASH: Excellent burning wood; in flame and heat, can burn while green due to low 50% GMC. Ash trees shed smaller and larger dead branches which gather underneath the tree. Dying before drying, these twigs and branches make great firing because of their very low GMC.
CEDARS: good only when seasoned.
little flame. much heat, beautiful scent.
CHERRY: Slow burner with good heat. scented and does not spit.
HOLLY: Good heat, will burn when green, but best when let dry a few months. (Ancient advice was to cut next winters holly this winter
PEAR: Slow and steady, good heat and a pleasent scent.
PLUM: Good heat and scent.
WALNUT: Good heat and scent. Aromatic wood!
YEW: Among the best. burns slowly, with fierce heat and the scent is pleasant.
LESS DESIRABLE TIMBERS
ALDER: Opinion varies re usefulness, works best well seasoned and takes time to dry because by nature it grows in swamps.
BEECH: Best when it is well seasoned. Fell beech for future years.
BIRCH: Good heat, quick burn, bright flame. Nice smell. Works best when mixed with slow burners like pear cherry plum, holly.
CYPRESS: Burns well but quickly and may spit.
HAZEL: Good. But hazel has so many other uses you might not want to burn it
HAWTHORN: burns VERY hotly. This is a top timber but is slow to season. Should really be preserved for hedgerows and shelter
HORNBEAM: Good, burns well
MAPLES: Good or bad! Depends on variety. Sycamore is a maple.
OAK: Dry oak is excellent for heat, burning slowly and steadily. Season for 2-3 years.
PINES: Burn with a splendid flame, but apt to spit. Needs to be well seasoned. Give off a large number of resins.
PLANE: Burns pleasantly, but is apt to throw sparks if very dry.
RHODODENDRON: Thick old stems, being very tough, burn well.
ROWAN: Burns well
These woods are not recommended for use in wood burners
CHESTNUT: shoots embers. little flame, little heat.
DOUGLAS FIR: Poor. Little flame or heat.
ELDER: Mediocre. Very smoky. Quick burner, low heat.
ELM: Must be dry to use. Even then it smokes. more water than wood.
LABURNUM: Totally poisonous tree, acrid smoke, taints food. AVOID
LARCH: Crackles and spits, scented, heat fair, leaves oily soot in flue
LIME: Poor. Burns with dull flame.
POPLARS: Burn slowly with little heat – but make excellent matchsticks.
ROBINIA (Acacia): Burns slowly, good heat, acrid smoke. use with care
SPRUCE: Burns very quickly and with many sparks.
SWEET CHESTNUT: burns well but sends out sparks. Only use in stove with door closed!
SYCAMORE: Burns with a good flame and gives off moderate heat ... Useless when green.
WILLOW: Poor. GMC may be 200%. Willows must be dried to use and even then it burns slowly with little flame. Apt to spark.
Moisture content for any firewood MUST be below 25% and really should be as low as can be got. All felled wood will season naturally (by air drying) unless it is stored in a pond.
Natural seasoning can take many years for timber left to its own devices, but crosscut billets and blocks, well managed, may dry to 15% in less than 12 months and when split will dry even more quickly, depending on storage and the prevailing weather conditions.
I am obliged to Quora for the following which has been tailor-edited by me for this article:-
"A fully grown oak tree can transpire 40,000 gallons of water per year.
Water is used during growth and is absolutely essential for metabolism. H2O is split in to H+ and OH- elements and both are used to manufacture complex organic compounds".
Precisely how much water is thus utilized remains uncertain, but experiments suggest 5% is a reasonable guesstimate and that 95% of the water taken up from the soil passes right through to be transpired into to the atmosphere.
Think about this for a moment. A typical tall tree 100 years old (such as the sycamore felled at Hadrian's wall) will suck up to 100 gallons of water a day for hydration when it matters.
An acre of mature trees (1000) can lift 100,000 gallons of flood water out of the acre in one day while if the acre was in grass or scrub there would be almost none without run-off.
Living trees contain extraordinary amounts of water and the amount varies by variety and the ground under them. Moisture content varies from season to season in standing timber and also between different parts of the tree.
... insert the article about the felled tree and the planted saplings ...
Water evaporates continuously from the tissues of felled timber until the contained water is balanced by the humidity of the surrounding air. It has then reached its Equilibrium Moisture Content. Although EMC is both changeable and variable, 30% is ballpark for the British Isles. Wood above 22%, although it will burn, and is generally dry enough to fire, wastes heat by having to evaporate its contained water and causes boat stoves to give off less radiant heat. The fire burns cooler and emits more smoke. This smoke causes a build-up of creosote in flues and emits solid particulates into the surrounding air.
This matters hugely in canal boats.
Creosotes boil about 230ºC and FLUE temperature should be higher than 120º which in itself is a useful indication as to the minimum temperature for running a stove and how to check it by measuring flue temperature about half way up.
"Heat gradient" means measurements taken at the bottom of the flue will be highest and at the point where thee gases reach the outside air will be lowest.
At this point it is salient to note that charcoal comes with less than 1% contained water and my restaurant grade lump-wood charcoal contains no creosote whatever.
Also my charcoal only burns for a few minutes when first ignited. From them on it glows and this is the real secret of my use of charcoal to heat my boat.
Carbon (from Latin carbo 'coal') is a chemical element; symbol C atomic number 6. It is nonmetallic and tetra-valent.
Freshly felled wood contains considerable and measurable amounts of water calculated as a percentage of the "Oven Dry Weight". Green Moisture Content indicates how dry the timber is at felling and during seasoning. GMC can range between 30% and 200% and between these extremes GMC depends on age when felled, species, growing conditions and the length of a piece of string.
Mature eucalyptus camaldulensis typically returns 45-50% GMC at felling which is MUCH too high for burning.
A WARNING ... (Eucalyptus is not for indoor use; Bark and leaves give off toxic fumes!) ... although properly seasoned it is excellent for outdoor barbies due to the high oil content of the wood, Once the wood moisture content equalizes with its surroundings it will contain about 10-15% water.
Above 25% most woods burn inefficiently, generate smoke and give poor heat. Wood periodically dampened (ie not specifically protected from rain!) dries quicker than wood in a dry environment. Surface dampness keeps cellular pathways open and moisture moves to the surface by osmosis, where it evaporates more easily during dry days. Thus, it dries more quickly and stays dry out in the weather than if stored indoors.
Having said that of course once it is down to ODC it will stay drier inside but only by a tiny margin
ODC Oven Dry Weight indicates totally dry timber such as carpenters and joiners would use. Totally dry timber is deemed to contain no water though this is not always the case and depends on various factors such as species, age, the merchant who sold it before it was fully seasoned and the long-term humidity of its storage point.
It has been determined that a cubic metre of freshly-felled oak contains over half a metric tonne (540L) of water, the water being held in the cellular structure of wood, which is made up of cell cavities and cell walls. 'Free' water is held in the cavities and 'bound' water in the walls.
There is no calorific difference between timber types based only on the Oven Dry Weight. But denser timber burns longer because of its higher calorific density. The only consideration for burning wood is that it should be as dry as possible.
If a tree is felled in winter, MINIMUM moisture content will be over 50% and, if felled in summer figures like 200% have been recorded for the wettest species. 'Wettest' coincides with types found by rivers and canals: poplars, willows, alders, but surprisingly not ash.
By splitting logs and/or cutting them to short lengths, drying rate is accelerated. But it is still going to take many months rather than few weeks. Cutting in winter when the sap has dropped into the roots is a good idea. The reason wood needs drying out is that when you put a log into a fire all the moisture must be driven off before the wood will burn and it must use heat from the fire to drive out all the moisture. Sometimes it uses ALL the heat!
But there's a further problem
Wet/damp/moist wood will not burn cleanly. It will pollute the air with "solid particulates" and deposit corrosive tar in the flue creating future fire risk if the user later learns how to max the heat.
How dry the wood needs to be to burn well will vary from stove to stove, but the highest moisture content should be less than 30%. 20% is acceptable. 15% is ideal. Drying to 30% usually happens within a year, 20% within two years and in ideal conditions those times may be halved. How long it takes dry depends on how the wood is dealt with. Ideally it should be split as soon as possible, stored off the ground outside in a place where air can circulate through and stacked to avoid water-logging. Vertical is good.
SPECIFIC CHARACTERISTICS OF TIMBERS
APPLE: Splendid. burns slowly and steadily when well seasoned, with little flame, but good heat. malus genera are all good
ASH: Excellent burning wood; in flame and heat, can burn while green due to low 50% GMC. Ash trees shed smaller and larger dead branches which gather underneath the tree. Dying before drying, these twigs and branches make great firing because of their very low GMC.
CEDARS: good only when seasoned.
little flame. much heat, beautiful scent.
CHERRY: Slow burner with good heat. scented and does not spit.
HOLLY: Good heat, will burn when green, but best when let dry a few months. (Ancient advice was to cut next winters holly this winter
PEAR: Slow and steady, good heat and a pleasent scent.
PLUM: Good heat and scent.
WALNUT: Good heat and scent. Aromatic wood!
YEW: Among the best. burns slowly, with fierce heat and the scent is pleasant.
LESS DESIRABLE TIMBERS
ALDER: Opinion varies re usefulness, works best well seasoned and takes time to dry because by nature it grows in swamps.
BEECH: Best when it is well seasoned. Fell beech for future years.
BIRCH: Good heat, quick burn, bright flame. Nice smell. Works best when mixed with slow burners like pear cherry plum, holly.
CYPRESS: Burns well but quickly and may spit.
HAZEL: Good. But hazel has so many other uses you might not want to burn it
HAWTHORN: burns VERY hotly. This is a top timber but is slow to season. Should really be preserved for hedgerows and shelter
HORNBEAM: Good, burns well
MAPLES: Good or bad! Depends on variety. Sycamore is a maple.
OAK: Dry oak is excellent for heat, burning slowly and steadily. Season for 2-3 years.
PINES: Burn with a splendid flame, but apt to spit. Needs to be well seasoned. Give off a large number of resins.
PLANE: Burns pleasantly, but is apt to throw sparks if very dry.
RHODODENDRON: Thick old stems, being very tough, burn well.
ROWAN: Burns well
These woods are not recommended for use in wood burners
CHESTNUT: shoots embers. little flame, little heat.
DOUGLAS FIR: Poor. Little flame or heat.
ELDER: Mediocre. Very smoky. Quick burner, low heat.
ELM: Must be dry to use. Even then it smokes. more water than wood.
LABURNUM: Totally poisonous tree, acrid smoke, taints food. AVOID
LARCH: Crackles and spits, scented, heat fair, leaves oily soot in flue
LIME: Poor. Burns with dull flame.
POPLARS: Burn slowly with little heat – but make excellent matchsticks.
ROBINIA (Acacia): Burns slowly, good heat, acrid smoke. use with care
SPRUCE: Burns very quickly and with many sparks.
SWEET CHESTNUT: burns well but sends out sparks. Only use in stove with door closed!
SYCAMORE: Burns with a good flame and gives off moderate heat ... Useless when green.
WILLOW: Poor. GMC may be 200%. Willows must be dried to use and even then it burns slowly with little flame. Apt to spark.
