Using a Dremel rotary tool and various diamond bits I engrave roofing slates. The standard size is 225mm x 395mm and 4mm thick. The exposed slate is a lighter shade of grey and gives a contrasting image. However when the slate gets wet the etched areas darken.  Slates can be painted. Please see the painted slates in the shop section.  Slates come with a pack of 4 black screw cover caps included in the price.