That haze is usually some wheat paste leftover from the old dayz. Paints sucked pre WWII so may plaster walls were originally papered, and wheat paste was the thing.
Some times ( read often) that was papered over with newer stuff.
Bare clean plaster sometimes gets a little brownish patina, sometimes it was varnished. But I have not seen actual clean plaster cause a bleeding problem. It's always something else.
Effervescence- that's another story.
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