In the hands of 16th century Venetian and some central Italian artists glazing methods were adapted to attain more adventurous effects. These tended to use the mixing principles stipulated in the previous section., and usually presupposed an overall coloured priming, on which highlights of the motif could be laid in with thick opaque lead white. But areas of the priming, often brown or green, would be left as reserve between these. Glaze layers would be applied over both to create stronger lighting effects than the similar- colour method would permit. For example, a brown primer could be underpainted with thick white highlights representing drapery folds, and then the whole passage might be glazed over with blue or green. The result would be that the white would shine through these glaze layers as blue or green lights, whilst the brown primer would convert a blue layer, as a colour to which it is a complimentary tint, to a rich bluish grey, and would convert a green layer to a deep greenish gold. Baroque artists developed the method of white underpainting of highlights, particularly in rendering flesh. If a nude was underpainted in white on a reddish primer, parts of which would be left as reserve, successive layers of thin pink and orange would appear bright and warm on the white highlights, but would look deeper and cooler when placed directly on the primer. This was later dubbed “making optical greys”. It can be often found in works of Rubens.
