why does firewood spit and crackle so much?

Answer 1

because it is made from wood - and was once a growing tree, with fine tubes in it to carry liquids.

when it dries up, there is still some liquid left within the timber. its held together by a network polymer, lignin.

each of the fibres making up the wood, has hollows within it, which insulate the water inside the log, from the flames, but as they slowly heat up, the water turns to steam, and expand. slowly the wood is burnt, and pockets of high pressure resin and steam burst through, with a 'crack' sound. occasionally, bits are thrown off with this explosion, causing spits.

These miniature explosions from igniting sap vapour - are much more likely from burning evergreen timber. With some wood, conifers eucalyptus etc, there are oils that 'explode as well. In Australia, Koala bears, which live on eucalyptus trees, are highly flammable, and tourists are banned from approaching them with cigarettes alight.

Answer 2

Basically it is the sap in the wood that has not dried out properly. Also soft wood (spruces as one example) spits and crackle far more than does hard wood (oak).

However, here is lovely rhyme for you to enjoy

Beechwood fires are bright and clear
If the logs are kept a year
Chestnut only good they say
If for long it's laid away
Make a fire of elder tree
Death within your house will be
But ash new or ash old
Is fit for a Queen with a crown of gold

Birch and Fir logs burn too fast
Blaze up bright and do not last
It is by the Irish said
Hawthorn bakes the sweetest bread
Elmwood burns like churchyard mould
Even the very flames are cold
But ash green or ash brown
Is fit for a Queen with a golden crown

Poplar gives a bitter smoke
Fills your eyes and makes you choke
Apple wood will scent your room
With an incense-like perfume
Oaken logs, if dry and old
Keep away the winters cold
But ash wet or ash dry
A king shall warm his slippers by.


www.trees.org.uk

Answer 3

Sap doesn't go away after the tree is cut, but it does dehydarate a bit. When firewood is burned, the spitting and hissing and crackling is partly from the wood being burned, and also from the sap and moisture steaming. Sap and moisture trapped between wood layers will steam, them explode, much like a kernel of popcorn, making that popping sound.

Answer 4

Most firewood contains at least a small amount of resin; when this heats, it creates a tiny explosion, and this is what you hear as the spitting and crackling of a fire. Trapped water can make similar sounds, as can trapped air when it expands.

Answer 5

Sap trapped in the wood reaches the boiling point, the vapor expands and pops open the wood with a bang or pop. A pleasant sound when sitting around a campfire at the end of a hard days hunt.

Answer 6

your wood has alot of air and moisture in it where you got it from must not have let the wood age after cutting which gets most of the moisture out and I've heard of some places drilling holes in the wood to release some of the airpockets

Answer 7

green wood does that
green meaning not dried or cured yet.
has sap and moisture in it..
as wood dries out it burns faster and does not crackle ect...

green wood burns slower....

Answer 8

Because it contains water/sap and needs to dry out before you burn it.

Answer 9

all depends on the wood.

Answer 10

Its airpockets and moisture my friend. :o)