Close-up of the upper scene on the east face of the northern pier.
There seems to be no sign of either polishing or painting on this monument. Other monuments in Rome have a thin layer of coating on their surfaces - scialbatura - which some have argued is a deliberate coating added by the Romans or later while others have suggested it is a natural biproduct of stone degradation. Where this coating is found toolmarks are much better preserved, so whatever its origin this coating is certainly protective. There are no signs of scialbatura on the Arch of Trajan in anything like the quantities it is found on the Column of Trajan though.