The Sgraffito (mean scratch) is use to dig patterns, grooves or to make lightly texture hollow out appear or sculpted effects on inside or outside wall.
Apply a first coat of tinted lime render. Let it dry and apply a second coat of 2-3mm thickeness of lime putty and marble dust.
Draw the pattern by tracing or directly if your a good drawer (it's not really my case). If you haven't got the time to end the whole job in one day, take care to cover the surface where you work with wet rag or plastic.
You must chose well the time when you scratch (fresh, half dry or dry). Most of the time we work on wet surfaces. In fact the work on wet matter, is more porous and more absorbent and let darker mark. If the surface is drying the effect of the scratching will be more hatched and the aspect more intense. For this you won't need specific tools, you can use paint brush, scalpel, shaving blade or whatever you may find handy.
Usually a lime paint is used after to enhance the final effect.
In the future we'll do one together as you can follow the different steps