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Smalti - Filati Technique
Written by Rochelle, April 2011


Smalti is a type of glass paste, (sometimes it is translated as enamel), that was developed centuries ago to enhance, and then ultimately take precedence over colored marble in mosaics. 
Today, the dominant producers of smalti are all family owned businesses: 
Orsoni (Venice, Italy), Dona (Murano & Spilambergo, Italy), and Perdomo (Cuernavaca, Mexico). 
It is hand made in small batches, each color poured and cooled in small puddles,  about 3/16” -1/4” in thickness. 
In Italy they call these puddles of smalti “pizzas”.  In Mexico, they are called, not surprisingly, tortillas. 
The Italian smalti is thicker, and is turned on its side where the richness of the colors can be fully revealed. 
Due to the air bubbles that naturally occur in Italian smalti, and also due to tradition, one does not grout works made in Italian smalti as it settles into the bubble holes and creates a horribly ugly surface – think bad skin disease! 
Mexican smalti can be used on its side or with either the top or bottom surface facing up. 
Mexican smalti, lacking the air bubbles that Italian version has, can be grouted.

Cutting Smalti

Traditionally, smalti is cut using a “hammer” and a “hardie”. 
 This tradition goes back to at least the 2nd century Roman era
(there is a bas relief sculpture showing artisans using these same tools).  |
As mentioned earlier, smalti slowly took over the tradition of using colored marble in mosaics. 
Smalti, being more of a glass paste, is not as brittle as the glass most people today are familiar with. 
 Therefore, as the mosaic materials changed from marble to smalti, the method and tools of cutting tessare did not change, and thus a complete re-tooling of the ancient mosaic industry was averted. 
Henry Ford himself would have been impressed!

In my micro mosaics that are not made with filati, I use the hammer and hardie to cut my class.


Filati is typically made from smalti, rather than other glass. 
It is different from other rods in that, again, it is handmade, with each pull resulting in a unique color, never repeated. 
The artist can customize the filati as she/he sees fit. 
Traditionally, filati was made to create micro-mosaics. 
 The Vatican took a keen interest in the development of filati to replace all of the paintings, save one,
in the nave of St. Peter’s Basilica in Rome (the heat and humidity began to rot the masterpiece paintings, all of which were replaced by exact replicas in micro mosaic that are so perfect, most visitors fail to realize they are looking at mosaics rather than paintings). 
As the fashionable and polite society of the mid-1600’s through the mid-1800’s sent their “20 somethings” on a Grand European Tour, the demand for souvenirs (micro mosaic jewelry and snuff boxes being the most popular), grew immensely.  In the earlier days, one would create an image using single colored filati, typically in a simple lozenge shape, to painstakingly create delicate and elaborate imagery on a very small scale. 
Usually the images were based on tourist sites, for instance the Coliseum. 
As the demand for these increased, methods were developed to speed up the production. 
Still all handmade and pulled, artisans began using what in Italian is called “malmisticato” – or “badly mixed”.  
This approach would blend more than one color together, creating a marbled effect in each rod. 
And, in addition to the small lozenge shapes, filati would be made into circular, square, rectangular, tear drop, leaf
and c-shapes. 
Again, as the desire for more realistic and exquisite imagery increased, artists could now use, for instance, a malmisticato filato in the shape of the letter “c” and use it to mimic the hair of a person or the fur of dog – one piece of glass rather than the 10 or so pieces it used to require.   
Traditionally, the filati would be between 1 and 3 mm in size.  In my work, I tend to stretch the limits of size – at times going as small as a thread.  Also, traditionally once the filati have all been set and the adhesive dried, the micro mosaic would be ground down to create a very smooth surface.  In my work, I prefer the rough edges which reflect and refract light in such a delightful manner that I cannot imagine grinding that all away!

Adhesives and Supports

The traditional adhesive used in ancient mosaics was a mixture very much like our modern cement.  As mosaics became more refined, they required smaller tessare, and therefore an adhesive that wasn’t as clumsy as cement.  For micro mosaics, artisans would create a “stucco” from powdered marble, lime, and linseed oil.  They would blend, and knead these ingredients into a paste, and then store it in a wooden box for 1-10 years (!!), until it was fully dry.  Then they would chip out a chunk, grind it down and add linseed oil to create the perfect consistency for the filati to be supported. Needless to say, ancient and Romantic timelines are very different from our modern demands!  Usually I use window putty to place my filati in – it is remarkably similar to the texture and consistency as the traditional stucco.  This time-saving “trick” was passed on to me from the masters in Italy working in micro mosaic where I was trained.

Traditional supports for filati were shallow boxes made of marble, granite, ceramic, glass or fine metals.  Today, many micro-mosaics use a wooden or metal support.  I use wood or silver.

In the mosaics where I did not use filati, my supports are wood, painted black.  The adhesive is clear silicone.