Mosaic FAQ

Orsoni is the Smalti manufacture in Italy since 1888, and that is how they make the adhesive.

Ingredients: 10.6 OZ of flour \ a spoonful of honey | Half a spoonful of glycerine | A spoonful of gum-arabic

Put all the ingredients slowly into a large saucepan together with 1.75 litre of water, stirring until the mixture is even. Simmer while you stir it slowly and continuously for about 45 minutes without ever allowing it to boil. After turning off the gas, continue to stir it until it is completely cold in order to avoid hardening of the surface. In the end the mixture should have the same consistency as a sauce or mayonnaise. The glue can be laid on the sheet of paper/fabric with a brush, or you add the glue to tesserae with a stick, you can always make smaller quantity with the same proportion mentioned above. 

As the US Purveyor of Mexican smalti (www.Smalti.com), I would like to add my 2 cents about the differences between Mexican and Italian smalti. I use both! I love both! And I know all of you either will or do too!
The first and largest difference is cut. Both techniques pour a puddle of molten glass. In Italy it is called a pizza, in Mexico a tortilla. The Italian pizza is poured to a thickness of approx. 3/8", the tortilla 1/4. The Italian smalti poured thicker and cut into thinner pieces to expose the inside of the pizza. This inside (riven side) becomes the working surface of the material. By exposing the inside of the glass you will receive more vibrant, consistent, and reflective color. The pieces are more consistent in size on the visible working side but less consistent in thickness. Due to the varying thickness of Italian smalti in order to have a finished project with a smooth surface it needs to be set in reverse. (The reverse method is only required if you are looking for a smooth finished project.)
Mexican smalti is cut larger into irregular squares ranging from 1/2" to 3/4" on the visible working side with a fairly consistent 1/4" thickness. It more resembles a piece of tile. The working surface of the Mexican smalti is the top or bottom of the tortilla and has a fairly smooth surface without bubbles. It can be set direct with or without grout, because of its smooth surface, consistent thickness and lack of bubbles. Many artists including myself will set the Mexican smalti on edge if they are looking to add texture to their project.
Now on to color. In Italy, they have been making smalti for centuries. Their focus in regard to smalti is on the purity, brilliance, quality and consistency of the colors. To maintain these qualities the smalti pots are changed regularly and great care is taken in not contaminating the colors. The recipes are handed down and the making of the smalti is as much an art as it final use.
Mexican smalti is young by comparison. It has only come into existence in the 1950's. The production of Mexican smalti came through collaboration between a couple Italian Mosaic masters and a Mexican business man. There was a huge demand to fabricate murals and other mosaic decoration in Mexico during this time. Combining Italian recipes and new cutting techniques Mexican smalti was born. The direction of the "new" smalti material was to create a smooth surface with a hand cut feel, so that they could fabricate murals and other public installations with a smooth surface. They blended the Italian recipes but poured them thinner not to waste the material because they were using the surface not the riven side. In doing this they realized they discovered the rich mottled beauty of the surfaces of the glass. Less focus was on the recipes and pure color and more was put on the mottled painterly look of the tortilla. Often each side of each piece will be a different color and many different tones of the same color will come from each batch.
Because they are looking for the mottled color smalti "pots" are not changed regularly. When one color is finished, a new color is mixed and the two begin to blend creating the mottled color. As an artist and retailer of Mexican smalti this is a blessing and a curse. It makes for such beautiful color variations in a single batch, but makes it more difficult to reproduce colors from one batch to the next. My advice when ordering smalti is always order more than enough to finish your project colors do vary particularly in the case of the Mexican smalti.
When deciding which to use for you particular project, it can be as simple as this. If you are doing an installation or require a smooth surface it is easier to do this with Mexican smalti. If you are looking for texture and reflectivness, Italian smalti can't be beat. Or you can do as I do use both!
As for price, in the US they are fairly equal.
I hope I have added some insight to your choices in the future.
Answered by: Kim Wozniak (USA)

“Smalti” is the Roman word for “melt”. Smalti is hand-made in Venice and until recently there were only three families still making. The recipes and techniques have been kept secret and handed down through the generations. Glass is melted in a cauldron, then poured out onto a metal sheet where it is pressed down like a pizza which is then sawn up into little briquettes about 2 x 1cm (3/4 x ½ in). It is supposed to be used with the sides uppermost, thus emphasizing its rippled surface. Tiny air bubbles in smalti are part of its intrinsic quality.
Smalti can be bought as a 20kg irregular mix box, known as “roti”. This will contain tesserae that have a curved edge – these are the edges of the “pizza”. Purists would argue that these shouldn’t be used, but I find them invaluable for details.
Hand-made smalti is very expensive, but it makes a lovely addition to any mosaic and can be incorporated in small quantities.
Because of its uneven surface you do not need to grout smalti when working direct. It “self grouts” – as you push the smalti into the tile adhesive, it is forced up between the gaps in the smalti.
With Mexican smalti both sides can have a different coloration and one side usually has a patina on it which is to do with the cooling process. The molten glass is poured onto a metal plate, which is a conductor of heat so that side stays warm, whilst the top of the “tortilla” is exposed t the air which isn’t a conductor of heat. (It’s rather amusing that the Mexican’s call the smalti ‘cowpat’ a tortilla whilst the Italians call it pizza!) The side that is exposed to the air cools at a different rate to the underside that is touching metal and that is why sometimes you get a patina; always with the Mexican actually which has the most beautiful patina on it. It’s irregularity means that it is more fiddly, but I like it a lot. The Italian is more regular generally 1 x 2 cm briquettes so it is easier to use in a way. Here in England. Mexican is more expensive because we have to ship it from Mexico, which is a long way away and pay import duty on it whereas Italy is nearer and because we are in the RU (European Union) we don’t have to pay import duty on it. So here the Italian smalti is cheaper but in America it is the other way around – the Italian is more expensive than the Mexican.
I like both, it just depends what I am doing as to which one I choose.
Answered by Martin Cheek (England)

Q. History about mosaic
Emperor Diocletian in the beginning of the third century issued a decree establishing rates of pay for the various grades of mosaic artists. And in 330 A.D. Emperor Constantine transferred the imperial seat from Rom to Byzantium and granted mosaic artists tax exemption to encourage them. The technique of gilding tesserae in the Byzantine era, by applying a fine gold leaf to a sheet of plain or tinted glass about 8 mm. thick, covering it with a layer of powdered glass then firing, the resulting materials was ideal for producing colour effects because the unevenness of the powdered glass and consequently of the overall thickness created variations in tone and enabled gold to be used on very large areas. The popularity of mosaics began to decline in the thirteenth and fourteenth century being superseded  by painting on canvas and frescoes.

 

Q. What is Revenna technique?
This method is also called the Double Reverse method (the mosaic is set on lime putty, gauze is glued over the top with home made glue or weldbond and when it is dry the mosaic is lifted off the line bed and set onto a base with cement. When the cement sets the gauze is removed. This is used to make a reproduction copy of ancient mosaics or where you need a 'flat' surface but use irregular thickness tesserae.
Q. What is the Lime and how do use it in Revenna style?
Limestone past is Lime soaked with water to form a putty. With lime you work face up meaning you see your finished work, this is important for portrait work and you do not need to worry about cutting your tesserae to the same depth as in the Vincian technique.The tesserae will hold in the lime, you just press them in and they stay there. The great thing about the lime putty is you can remove tesserae if you want to change them. The replacement will still be held in place. When the mosaic is finished, glue the gauze on with rabbit skin glue, a water soluble type or diluted weldbond glue. You learn how much lime you need to remove by experience, just enough for the cement to attach to each tesserae.