This bowl is made of solid oak wood of local origin.
The outside is carved and stained with natural stains.
The interior is surface-treated with the finest sandpaper and polished to a silky sheen.
The wood is protected by a coating that is suitable for food contact. You can wash it with a soft cloth and soap. If it loses its shine, restore it by re-lubricating it with oil, preferably linseed or paraffin.