Bowls with shiny or hard finishes are somewhat more durable than those with the softer natural finishes. Their finish can be likened to a plastic film laying on top of the wood and fully encasing it.
For the most part since they have this hard protective barrier, they can be easily cleaned after use with soap and water.
However - should you notice a deep nick or cut develop in the surface coating which penetrates into the wood fibers, as can happen if using sharp knives, you should consider asking a craftsman to refinish the area or at least apply a protective oil to the area (as below). The key is to be sure to avoid trapping food in this nick to avoid bacteria growth.
These bowls are essentially "round bottom cutting boards." They are less likely to be damaged by constant use as their finish is more intrinsic to the wood, rather it is inside the wood and not on top of it as the hard finishes are. Although exclusive use of non-metal utensils in this type of bowl will certainly extend their life, it is certainly OK to use sharp metal knives or blades in them. They will get nicked and scored just as a butcher block does so they need a little bit more complicated care to keep then looking good and food safe.
It is best not to allow the bowl to completely "dry out" since a very dry wood surface easily allows 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 food service use, the oil film helps protect against food or other particles from migrating into the surface of the wood, thus reducing the opportunity for the growth of bacteria.
Simply put - these Salad bowls or Cutting bowls should be treated like butcher block cutting boards and kept clean and free of food contamination.
*Note: As with all food service items, be sure to practice good food preparation safety habits as described by the FDA.
FOOD SERVICE SAFETY TIP: If you think you may have left some food too long or wish to thoroughly clean the bowl, wash it with HOT water, dish soap and scrub. The FDA recommends sanitizing your wood products after washing by rinsing for several minutes with a dilute chlorine bleach solution of 1 tablespoon bleach to 1 gallon water. You can substitute a one to five dilution of vinegar if you prefer not to use bleach. Pat dry with towels and then, allow to dry completely before applying a liberal coat or two of oil.
Link to FDA info: Safe use of wood for food service.
