“The practices that are now called painting and drawing are entirely different that what they were in past centuries. Painting has died – its central techniques have been lost- four times in the history of Western art: once when the Greek paintings and textbooks were lost, again in the sixteenth century when Jan Van Eyck’s method was lost, again in the late eighteenth century when Venetian Renaissance technique was forgotten, and a fourth time in the early twentieth century when painting alla prima ( wet in wet) definitively replaced the more systematic Baroque techniques.
Renaissance painting was done in many stages, with each layer drying before the next coat, and the images were constructed: that is, planned in advance and brought to completion in a more or less systematic and deliberate manner. Different emulsions were used within a single painting ( a typical sequence was tempera, followed by oil and then glazes and varnish.) Nowadays artists paint all at once, alla prima, in a single thick coat. Even Romantic painting at the beginning of the nineteenth century, was definitively different from what is done now. the change happened as early as Manet and the Impressionists.
It doesn’t help to look in old texts, because Jan and Hubert Van Eyck kept their methods secret, and there is no Renaissance source that says how Titian executed his glazes. Nor does it help to turn to contemporary chemical analyses, because what is important about the technique – such as ultra-thin paint layers – cannot be adequately studied in infrared, X-ray, or thin section. Some German texts, written around the turn of the twentieth century, record attempts to recapture Renaissance methods-but even they have become hard to interpret as the traditions of reconstruction have died out. the fact is that oil paintings is a lost art several times over, and what we call oil painting bears very little resemblance to what past centuries knew by that name.”
Why Art Cannot Be Taught – a Handbook for Art Students- by James Elkins