The lighting of an icon lamp, like the flame of a candle, is an image and embodiment of the Light of God. The lighting of candles and icon lamps has a deep symbolic meaning. In fact, it is also a prayer; no less, and perhaps an even more important appeal to God.
The importance of lighting lamps was mentioned as early as the Old Testament:
"And the Lord spake unto Moses, saying, Command the children of Israel, that they bring unto thee pure oil olive beaten for the light, to cause the lamps to burn continually. Without the vail of the testimony, in the tabernacle of the congregation, shall Aaron order it from the evening unto the morning before the LORD continually: it shall be a statute for ever in your generations. He shall order the lamps upon the pure candlestick before the Lord continually."
It is customary to light lamps of dark glass during the fast days, and of red glass on feast days.
Altar glass candles
Unlike pendant lamps, table lamps are placed directly on a shelf in front of the images. As a rule, they are a vessel of glass on a metal base. This is done not only for aesthetic effect but also for safety reasons. The metal protects the surface the lamp is placed on and prevents the glass from cracks which may occur because of overheating. But there are also one-piece table lamps made of ceramic, for example.
