Bowls without a hard finish can be a little bit more complicated given that they are somewhat less protected by their softer wax or oil finish.
It is best not to allow them to completely "dry out" since a very dry wood surface may allow liquids or other contaminants to more readily penetrate and stay in the grain. If you think the wood is getting too dry simply coat the surface with Butcher Block oil. Mineral Oil is OK too but avoid maintaining with vegetable oils since these contain food products which can spoil and become rancid.
Why oil it?
Besides slightly deepening the color of the woods subtle grain structure, which helps show more of the woods texture, the oil in the wood fibers offers resistance against contaminants or moisture from getting into the wood and possibly causing stains or other minor damage. As such it is a good preventative measure. If you don't use the bowls for food service, nothing else needs to be done.
For info related to food service use - click here
