Three methods of cutting smalti are most common: nippers, hammer and hardie, or chopping machine. Wheeled nippers are pliers with 2 round carbide blades. The piece of smalti is placed between the blades, and a squeeze of the handles fractures the glass. Nippers are easy to use but can tire the hand and forearm muscles. They also have another drawback- they cut the glass to smoothly meaning that the cut glass does not refract light in the same way as a piece of glass cut by hammer and hardy. The more traditional method for mosaic making is with the use of a hammer and hardie. The hammers come in different sizes and weights. This method will also cut marble but the force required is considerably greater. I have used this method to cut the background on the Owl and Pussy-cat wall. The hardie is a chisel securely fastened in a wood block, see image below. The hammer is a variation on a the usual hammer and the heads come in different sizes and weights.
The tessera (small glass or marble tile) is held atop the hardie and then tapped gently with the hammer to fracture the glass. This technique takes much practice, but is much easier on the hands and arms than nippers. Once mastered, it is usually the preferred method, especially for larger projects. Cutting machines make the hammer and hardie into a production tool that requires only the turn of a handle to fracture the tile. For those who intend cutting there own smalti pizzas or marble, you may want to invest in a large piece of equipment like this. They can be bought in Italy or in China and are extremely effective for cutting large quantities of material. Again, it takes a while to get the hang of using the machine but it’s easy and effective. They are around 1400 Euros, so quite an investment for the home hobbyist.
Here is an image of a mosaic artist using a hammer and hardy. Hammers come in a variety of sizes and can have different cutting edges depending on whether you intend cutting marble too. This is a good video on how to hold and use a hammer and hardy. There’s a definite art to using these tools and practice is required. They are the preferred choice by mosaic artists because of the cut. It produces an uneven surface which allows the light to refract off the glass in unique ways. The other two methods tend to provide a flat cut surface which does not produce as desired an effect- machine cutting affects the crystalline structure of the glass. Ideally cutting machine should not be used for smalti.
For those who do not have the time, money or patience to use a hammer and hardy then often a simple nipper will do the job. They work adequately on small pieces of smalti, though the wheels will have to be changed with some frequency if you intend to cut large quantities of glass.
HAPPY -ARTING! and watch your fingers.