why do some woods crackle when they burn and others do not?

Answer 1

For the same reason that pops Orville Redenbacker's famous pop corn - moisture is turned to steam, expands and pops - oops, I mean crackles.
Some wood simply has a higher moisture content and a tighter grain to trap the pressure until it finally escapes with a snap.
For some reason, Rice Crispys comes to mind........

Answer 2

Most of the strength in the cells that make up the wood is along the length of the trunk, limb or branch. The strength across the grain is not so important to the ability of the tree to withstand its weight and wind loads, etc. Thus, there is considerable variability in cellular make-up across the grain in different woods.

This varaibility in cellular make-up leads to a greater or lesser ability to withstand the build-up of pressure during burning from water that starts as liquid in the cells and then, when heated, becomes steam. Where the strength is great enough to retain the steam to a high pressure before it escapes, the escaping steam makes popping or crackling noises.

With weaker cellular structure, the steam is able to escape before getting very hot, at a lower pressure, that makes little sound or a quiet hissing if you listen carefully.

Answer 3

Sap and other componants in the wood.

Answer 4

it is for their formation - nothing serious(by hard ness)

Answer 5

moisture level.....bugs, too...