Because the encaustic technique of creating icons was used only in earliest times, the following contribution will limit itself to the tempera technique (as was prescribed for Russian icons), and will then demonstrate the technique used for the "modern icons" of iconographer Alexei Saveliev.
The first icons were implemented in wax colours (encaustic technique). At that time it was the only technique used for painting icons.  Wax colours, however, give rather poor results.  
Around the fourth century, brilliant, transparent colours, more fitting for the icons, were searched for and eventually found. Clay and stones were ground to a fine powder and mixed with consecrated water to produce a thin consistency.  This paint mixture was then applied layer upon layer without use of a bonding agent and was finally sealed with oil. Later, the more convenient tempera and penetrating gold leaf technique used in art found its way into icon painting.  There are no dark icons and neither can there be any.  The dark icons we see today are simply very dirty or very fake icons.  The popular metal covering is later nailed onto the miracle-working icons in a most primitive manner, as a gift – most of these icons are from the Jugendstil period. 

 How an icon is created (classic, traditional technique of writing/painting) 
For a better understanding:

a) Tradition plays a central role. Tradition is not a rigid bundle of meaningless rules, but is manifested in Church life.  It relates to Jesus Christ.                         

b) The icon and the Holy Bible share a very close relationship.  This close connection requires that the icon is written (painted) according to given rules, that it is signed and that it is consecrated according to certain rites.  

c) The icon is therefore not a subjectively perceived, arbitrarily interpreted picture, but a theological sign language thought out by the Fathers of the Church, the canon of which is laid down in painter's manuals. Certainly, the iconographer had a certain amount of freedom of expression, but formally he was bound to observe the icon’s purpose.  Only then will theology, the word of God, reveal itself – not only in words, but also in pictures.   
d) Just as the symbolic content of the icon is binding, so too the painting or writing technique in egg tempera is subject to rules set forth in prescriptions and manuscripts. Some terms of old prescriptions had been misunderstood or incorrectly copied during text transmissions and been treated arbitrarily ("lived Gospel” and classic icons are the best teachers of  iconography).

e) Symbols are representative images and signs that draw attention to an invisible yet significant world of ideas beyond the icon’s pictorial content.  Symbols in icons are a means of bringing the unthinkable into the realm of the tangible (symbolein =  bringing together). The “light”, a symbol in all cultures, is seen as being characteristic of God and his son Jesus Christ, the  " light of the world ". Thus, the mythical sun god Helios of ancient religions, which was adopted by Christianity, became Jesus Christ Jesus Christ, our figure of light.  Light and darkness are contrasts which are united in the aureole (mandorla), the halo that surrounds the risen Christ.  

f) Entering an Orthodox Church is tantamount to entering the spatial icon, symbolizing the connection between the invisible cosmos and the spiritual world that has become matter. Thus, when painting an icon the iconographer usually begins with the gold background which represents the uncreated, unimaginable cosmos and is a reflection of the heavenly light in which matter appears as a sensually experienced "picture".

g) The icon, therefore, forms a connection from the visible to the invisible world; through the icon, it becomes possible to experience the invisible world, which does not have to even resemble the visible one.  Perspective and anatomy are virtually eliminated; instead, abstract means are used to create a reality which can be experienced only in “meditative contemplation”. 

h) What is of importance in the icon is presented boldly, what is less important is presented on a much smaller scale.  IMPORTANCE OF PERSPECTIVE!

i) In contrast to the central perspective of profane pictures in which all lines of perspective are concentrated on one point (focal point, vanishing point) in the picture, the icon’s vanishing point of the REVERSE PERSPECTIVE diverges at the back of the picture, emphasizing the momentousness of cosmic infinity, and converges at the front of the icon (the vanishing point - eye of the viewer), making it possible to get closer to the event (salvation) by drawing closer to the icon.  .

j) When the iconographer ‘opens up’ the icon, he begins with the  d a r k e s t  c o l o u r s, which he interprets as the shadow of Hades (the underworld).  Simultaneously, from this ground, by using increasingly brighter colours, he forms the light.   From this we can conclude that the icon knows no source of light outside itself, but passes on its light to “those standing in darkness”. 

k) The egg, an important symbol, stands for life, resurrection and for the iconographer it is the bonding agent for his pigments! (see also K.and  B.Kegelmann, School of Icons, Münster, 1998; Helmut Fischer, The Icon, publisher: Herder-Spektrum).

1. Condition: the bare wooden board

-Selection of a resin-free wood such as oak, alder, birch, cypress and certain others; insertion of cross ribs in the case of large, constructed boards to avoid warping at the back of the board; hollowing out of the board to produce a sunken surface within a frame; occasionally: covering the surface to be painted on with canvas (later also with paper) for stability; roughening of the wood.

2. Condition: the ground

- Application of the grounding in several thin layers and subsequent polishing; components of the grounding: chalk (alabaster), animal glue etc . (Russian: levkas); the board then appears white. 

3. Condition: the sketch

- Either sketching of the outline with a brush (Russian: risunik) or etching the contours with a pencil (Russian: grafija), using as examples either older icons or painting manuals containing sketches (Russian: podlinik), illustrated manuals or text descriptions with references to colour and inscription. .

4. Condition: painting with tempera colours

- Application of the colours; colour components: earth or natural colours plus egg yolk plus a thinning liquid (often Kvas, a kind of beer) in certain proportions; application of colour layer upon layer, proceeding from the darkest to the lightest colour; use of vitrifiable pigments (Russian: plav) if the lower colour layers are to shine through, by means of a  blurring of the layers..

5. Condition: Olifa coating

- Application of the so-called olifa layer for better preservation and polishing of the blunt tempera colours; olive or linseed oil, resin dust, possibly amber dust; these provide protection of the icon from incense, humidity and oil lamp soot, but also result in its darkening through the attraction of dust particles.  It is possible, however, to restore the shining colours of the icon through careful dusting.  

- Application of gold leaf before painting;
- Icon coverings: silver or tin silver frames (basma);
- Metal coverings around the body contours (oklad); metal covering over almost the entire icon apart from the “incarnate”, i.e. face and hands; old icons with new coverings – leading to the complete decay of     iconography (transfer pictures ...)

( Source: Russian icons, Dr. Tatjana Högy, unique special edition published by order of  International Guild, Munchow University Press Schmitz in Giessen).