The names sound difficult but they are very friendly 
First I thought that there should be English words for mosaic theory… but after a while I accepted fact Italy is home for mosaic and some Italian words would not hurt me.
I did some research, I found many people wrote about opera. There is nothing to be scared, the most important part is to understand the idea.
I love specially article by Bill Enslen. He is exactly what I need, 100% of information written in short light way.
http://www.articlecity.com/articles/hobbies/article_1537.shtml
Andamento (Italian for “flow”) is the visual movement of your mosaic created by placing tesserae in specific patterns to achieve the desired image (a.k.a. “coursing” your tesserae (mosaic pieces)).
Opus (Latin for “work of art or literary work”) is any work in any creative field, such as literature, architecture, music, and fine art. In our world of mosaic art, opus refers to how we arrange our tesserae. Different opera (the plural of opus) result in different flows. Understanding the various opera allows you to properly plan your work to ensure you achieve the desired look.
The following opera terms are based on Latin. It doesn’t matter what you call each style. The point is to be aware of the types of opera, then plan which types give the results you want, and then create your masterpiece accordingly.
http://www.thejoyofshards.co.uk/glossary/index.shtml
http://www.drostle.com/mosaicstyle.html
Opus Regulatum, Tiles laid in a regular grid pattern are called regulatum. This is a very regular pattern of tesserae, like squares on a chess board.
Opus Tessellatum, regular brick pattern style (horizontal or vertical) which immediately introduces an element of direction into the tile laying.
Opus Vermiculatum, from the Latin ‘worm-like’ is the most expressive form of mosaic tile laying. The tesserae are laid along the contours of the image, describing its form, you should be able to make a rubbing of the mosaic and see the design. The whole image is given a dynamic power that is unique to mosaics but which is extremely labour intensive and takes a high degree of skill to do well. The essence is to begin with a tesserae size and complete the mosaic in flowing courses of tesserae of that size.
Opus Sectile /Florentine, This technique is used extensively in Islamic tile design where it is known as ‘Zillij’. The tiles, usually larger glazed ceramic tiles are cut into shapes that describe the form, i.e. an eye shaped tile would be used as an eye. This usually has a great effect on the tile size to design scale, requiring relatively larger tiles. The technique is closely allied to marquetry.
Opus Palladianum, This technique gives a more modern feel. The tesserae are cut into haphazard shapes and laid like crazy paving. This buzzing texture is also used for backgrounds but is labour intensive if done well.
The Mixed styles
Of course having defined style there is no reason to stick to just one. The main style used in Roman mosaics is defined as Opus Classicum:
Opus Classicum, As its name suggests this is the traditional style found in many mosaics from the great Roman mosaics of the Levant to the many Victorian Classical floors that can be found here in England. The technique combines opus tessellatum with vermiculatum. The main objects of a design are created in vermiculatum and these are placed on a more regular, tessellated, background. Where the two meet the background takes the form of the object, so each object has a background halo around it. This technique creates a very strong sharp and clear image.
Opus Spilimbergo, Named after the world renowned school of Mosaic Art in Friuli this truly contemporary style uses texture, light and differing tesserae sizes to create a dynamic and expressive form. Best suited to work in marble and Glass Smalti this approach to mosaic is the height of contemporary practice.
http://www.mosaic-tile-art.com/mosaic.html
I also recommend this book Mosaic Techniques & Traditions by Sonia King.
There are the pieces I value a lot. http://books.google.com/books?id=g3JT9c50VkoC&dq=mosaic+traditions+%26+techniques&source=gbs_navlinks_s
More information about colors http://www.glassmosaictileart.com/chapter6_page01.html
Characteristics of Color
A color is described by its hue, intensity, and tone (tone is also known as shade or tint).
- Hue: The basic color, such as red, yellow, or blue (i.e., the wavelength of the electromagnetic spectrum that appears most dominant).
- Intensity: The brightness or dullness of a hue. Saturation is a measure of the hue’s purity (i.e., whether the hue contains a narrow or
wide set of wavelengths). Increasing saturation makes the hue vivid; whereas, decreasing saturation makes it look dull and gray.
- Shade: Modification of a hue by adding black.
- Tint: Modification of a hue by adding white.
