As the Arc is an open flame product, is it natural for this to tarnish a little over time and this is a normal expectation of the product.
You can however clean this in-between uses.
To do so, we recommend using warm soapy water or a non-abrasive bleach-free kitchen cleaning spray or wipes to clean the external parts of the oven.
DO NOT us any abrasive cleaning products or abrasive sponges/cloths.
To clean the stone, we would recommend leaving this on full flame for 60 minutes which will then burn off any residue on the stone.