Years ago, I was reading an early 20th Century book on house painting and there, amidst the many ads for “high quality, high lead” paints and “natural horse hair bristle brushes” was a little snippet on painting porch ceilings. “Sky Blue” was the preferred color for porch ceilings, the article said, because it was a known fact that mud daubers and wasps would not build a nest against a blue ceiling.
One hundred years ago, front porches were a big part of American culture and they became – in a way – auxiliary living rooms. Elderly folks have told me that when they were little kids and it was raining outside, their mom would send them out to the front porch to play – for the day!
The porch was a place for social gatherings, too. City sidewalks bustled with pedestrians moving to and fro, and front porches provided a window on the world and a place to chat with neighbors and catch up on the local happenings.
Front porches were comfortable, too. Before World War Two, air conditioning was something you found at a few movie theaters. In these pre-A/C days, front porches (and their fresh breezes) provided a little relief from the summer’s heat.
And all of that could be ruined by a few stings from an angry wasp.
One hundred years ago, homes were built intelligently and thoughtfully, and everything builders did had a good practical reason behind it, including using the color blue on porch ceilings.

Thus far, no mud daubers or wasps have built a nest against my sky-blue porch ceiling on my newly painted home here in Norfolk.
I was told a long time ago that they always mixed a little arsenic in the porch ceiling paint, which gave it the blue look. Being up high and out of the way, it did not present a hazard.
But if you have painted with simply blue paint having no additives, then perhaps it is truly the color itself keeping away the wasps and dirt daubers and spiders.
Not being a chemist, I could not say if arsenic makes paint assume a blue tint.
That arsenic story sounds legit, and I think I’ve heard something about that before. Thanks for the comment!
Why Is the Porch Ceiling Blue? http://bit.ly/d1NH4Y Grew up with one, but didn’t know why it was blue. Now I do!
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RT @handsonhistory: Why Is the Porch Ceiling Blue? http://bit.ly/d1NH4Y Grew up with one, but didn’t know why it was blue. Now I do!
This comment was originally posted on Twitter