risers, italian porphyry

Porphyry risers may have natural surfaces when they are made from flat and thin hollow slabs with machined surfaces, or sawn off blocks (with the exception of flat, semi-gloss surfaces obtained from hollow quarry slabs).

Natural surface risers have a variable thickness, and need special attention when machining the external heads, which can be calibrated and machined like heads of steps. Risers are an integral part of steps are used to cover the vertical parts. Rises and steps are normally machined in the same way, although in order to attain special colour and visual effects they may be combined with different finishes.