View on Delft
Johannes Vermeer, 1660-62
In this painting by Vermeer, in particular the paint surface of the red tiled roofs is completely covered with white-translucent globules that have erupted through the dark red paint. In the past these protruding lumps were interpreted as chunks of lead white pigment and/or sand grains. Recent research has demonstrated that they are the result of lead soap formation and aggregation [Van Loon 2009].
Pertaining questions are what are the circumstances for the metal soap and aggregate formation, what is the timescale of the development of the aggregates, and what can enhance their formation, and how does the presence of these aggregates affect the stability of the paint.