Opaque White as the base coat of a highlight makes the highlight visible when there is no lighter reflected light directly behind you. This yellow and dark red coloring in the dark reflection is me.  In  this technique the shadows are left clear and shiny.
 
 

I get the best dynamic effects with a matte finish. You could never get the effect on the right with a gloss finish.

When the reflected light by contrast is so bright as to make the white paint appear black. This is what you get. By example, an opaque dark (there are none in this painting, only white) will stay dark, but a transparent dark (no opaque white) can be the lightest passage in the painting if the reflected light angle is just right. As in this angle.
 
 

Pictura translucida was then and is now a painting technique using transparent and opaque pigments in tandem on a shinny metal support panel. This produces the most amazing dimensional effect with light. I see why this was called the most beautiful form of painting in the first century. 

A/D 500 CONSTANTINOPLE,  What was happening with sculptures and buildings during this time? A lot! The Hagia Sophia is a good example with four pendentive pillars that held up the dome, an architectural achievement by Justinian, successor to Rome in the sixth century. This is the First Golden Age of Byzantine, 
A/D 700 CONSTANTINOPLE, The Lucca Manuscript describes some little known forms of art, one called "Pictura Translucida", which was transparent resin mastic or lacquer medium with transparent pigments painted on polished tin plates. 

At this time there were artists that were making paintings more beautiful than ever seen today. They had not only a complete opaque palette, but a complete transparent palette as well. By today's standards the colors were not permanent but they had all of them. They could make a halo or face glow by adding intensity to the color through reflectance from the shiny surface support.