Cavo Reliveo is sometimes called 'sunken relief'. It's a relief in which the highest point in the carving is below the level of the original surface. The Egyptians were masters of this form of carving and we've seen this technique before in the Pizza Paddle project.
Because 'cavo relievo' literally means 'hollow relief' in Italian, it's sometimes used interchangeably with intaglio (from the Italian to 'cut, incise'). Intaglio also involves carving below the surface but is usually 3-dimensionally in reverse so that an impression from the design yields the image in relief. Most often seen in print making and engraving
A strong outline is particularly important for cavo relievo as it lacks the natural shadows that arise from being lifted from the background. To help with the deep outlining trench, I make a special carving tool. Don't worry - it's dead easy!
Drawing and my tool list in the download below: