Casting porosity is bad

Back in the day when we drove the Nimitz freeway regularly we laughed when we saw this sign:
My father always said, "I don't want any of you guys to cast any porosity around me."

DelQuilts did a blog essay on July 18 telling about a strange sign she saw along the freeway. The sign said, “Distilled yet not reduced.” Huh?

I found out there were some archive references to the “Stop Casting Porosity” sign at: http://catfishstew.baseballtoaster.com/archives/156477.html by Ken Arneson, and a picture of the sign at: http://setiathome.ssl.berkeley.edu/~davea/porosity.html

Nowadays there is still concern about casting porosity. See: Western Sealant.