Eric. OK, my friend, I have tracked down the source, a film that showed a few years ago:
Tim's Vermeer - Wikipedia
Vermeer will always be a mystery for a number of reasons. We know so little of him. His paintings were so much of one type. He produced so little. His skills were amazing. Check out the film. I will be re-watching it tonight. And remember that I am only the messenger. ;o)
Proost
PS - Some criticism of this possible technique that may have been used by Vermeer is being echoed today re AI and photography. It never fails to amuse that one persons "art" is so much more real and so much more valid than another person's "art." These arguments get trotted out with every new technology and are not new, and to quote the noble English poet,
"Tomorrow, and tomorrow, and tomorrow,
Creeps in this petty pace from day to day,
To the last syllable of recorded time;
And all our yesterdays have lighted fools
The way to dusty death. Out, out, brief candle!
Life's but a walking shadow, a poor player,
That struts and frets his hour upon the stage,
And then is heard no more. It is a tale
Told by an idiot, full of sound and fury,
Signifying nothing."