The oldest mosaic technique is the cut technique.It precisely consists of cutting the mosaic material (natural stones or enamels)with the help of a special mosaic hammer (martellina) and of a harotic fixed to a wooden log (hardie)tagliolo in italian. Since antiquity,the hardie and the mosaic hammer have always been the basic tools used in mosaic art.This can clearly be seen in a marble relief of the Roman Age (Ostia, Archeologica Museum) ,probably a shop sign,depicting in full detal two workers who are busy cutting tesserae and, in the background, the master-mosaicist showing two labourers where to put the sacks of mosaic material.The toos used by the two figures in the foreground are easy recongnizable :in their right hands they both hold a hammer with two cutting edges and strike blows on a piece of mosaic material placed on an anvil embedded in wood. Even today the hardie and the mosaic hammer are the tools most widely used to cut smalto pancakes and marble pieces into tesserae of the desired size .The traditional cutting method requires skill and practice but it also ensures that a clear precise cut is achieved.The material is hit and split into small pieces , thus obtaining,so to speak,the “mosaic basic unit of measurement” or the “the tessera”.The difficulty of this procedure varies according to the qualify of the material to be cut.As far as natural stones are concerned , it is necessary to follow their physical structure , in order to orientate the cut in the right manner.Enamels, instead, have a basic glass composition and their split is generally more complex because it is more difficult to control the direction of the cut.In order to obtain a clean and linear cut, the “tessera” must be held firmly and a single hard stroke must hit the surface.Often, in fact,and in the case of enamels, the cut may result in an irregular detachment.In antiquity mosaic material was cut into tesserae in the place where the decoration was to be executed.In the case of wall mosaics , tesserae were made directly on the scaffoldings , as can be inferred by the pieces of smalto pancakes found in the wall interspaces during restoration work condeucted in the Cathedral of Monreale . In this way the mosaicist could obtain teseare of the size and shape needed to fill the design and achieve the best aesthetic result.
Tesserae, either square, rectangular or triangular in shape, usuallyhad their edges bevelled to facilitate their placement in the mortar bed; the size varied from 2 to 20 mm, in side lenght and between 3 and 25 mm. in depth,although in the finest mosaics the tesserae could be cut to even smaller sizes by using a special nipper .