Seal or not to seal? What to do with the cracks in your logs.
It is virtually impossible to prevent logs from developing cracks and checks as they age and dry. That's because as a large piece of wood seasons, mechanical stresses build up until the surface stress becomes so great that the wood cracks. We call these stress cracks "checks."
Do checks need to be sealed? Depends upon the depth and direction of the checks. Upward facing checks can collect water increasing the interior moisture content of the log. If they continue to collect water and the wood remains damp, they can eventually result in internal wood decay as well as provide nesting sites for carpenter ants and other insects. It is not necessary to seal checks on the bottom half of round logs since they do not collect water. For a uniform appearance of your home, you may want to seal them as well. It is not usually necessary to seal checks or fissures that are less than 1/4" wide since they cannot accumulate that much water.