Cracking is due to one section of the wood drying faster than another
and shrinking faster as it dries (usually outside vs inside). Generally
the faster you dry the wood the more potential there is for cracking,
but there are vast differents in the type of wood. Apple for example
can begin to crack minutes after the tree is cut down.
Generally I take the safer route and coat the whole block / blank /
bowl and give it lots of time. Many people have developed methods to
speed things up and you can find plenty of them at sites like this or
on internet searches.
Brad
hardingpens.com