From the 7th century onwards coloured glass was produced by firing a mixture of metal oxides and minerals. This was known as pot metal glass. Later in our history one of the most widespread and sophisticated forms of glass production available for all to see was stained glass.
This all came about during the beginning of the 14th century when it was discovered that if silver stain (a silver compound such as silver nitrate) was applied to the back face of the glass it would produce patches of yellow or orange when fired in a kiln. Not only could the glass colour be changed, white to yellow, blue to green etc, but also with careful manipulation the same piece of glass could produce different hues.
If a clear piece of glass was coated with red or blue on the front and yellow on the back, a bit like a colourful sandwich, then when the front colour was ground away it would reveal the shining yellow from behind. This was extremely useful as glass with patches of yellow could be used to highlight halos, crowns, sun rays and hair.
Jan Van Eyck’s Magical Alchemy
Vasari credits Jan Van Eyck with inventing the technique of oil painting in the 15th century, when in the confines of his ‘alchemist’s lab,’ Van Eyck discovered that oil could be used as a medium to carry pigment.
The Schedula of the 12th century compiler Theophilus Presbyter however shows that this was not the case and that oil as a medium for painting had been looked at a lot earlier. Coincidentally Theophilus Presbyter’s second Schedula happened to deal with stained glass and the painting of stained glass.
Nevertheless history says that on discovering Van Eyck’s magical use of oils, the itinerant Sicilian painter Antonello da Messina rushed off to Italy where this new and sensational idea was readily adopted by not only himself but others, thus opening the floodgates to a painting revolution. So how does this all tie up?
Van Eyck’s Beautiful Dream
Whether or not Van Eyck invented oil painting is not relevant here, his biggest success was to develop the art of glazing, a sensational technique which would change the way paintings were produced. Looking at Van Eyck’s painting technique now we can see that it appears to be a natural continuation if not an imitation of the stained glass process but this time using oils.
Getting Down in Black and White
After priming the board, Van Eyck would execute his painting in earth tones of browns, blacks or greys with bright, white highlights. Working with immense skill and diligence a complete painting would be built up in stages without colour, similar to a sepia or black and white photograph.
Single or Double Glazing?
We know that when producing medieval stained glass, the dark outline of the figure was the final layer painted on top of the glass. Van Eyck’s innovative glazing process mirrored this stained glass technique but in reverse. With glazing, semi-transparent or transparent colours were painted over the black and white underpainting until a layer of thick, glassy vanish or glaze was produced similar to glass. Extra glazes would then be added countless times until the desired glossy optical effect and depth was produced. You can see an example of how I have used glazing on the painting on my home page. Look at the turban and the cardigan.
What I’m suggesting is that the roots for glazing in paint lies in an attempt to imitate the richness and depth of colour found in the production of stained glass windows but in oils. Don’t you agree?