SC - Building ovens

[Mark Schuldenfrei]

  "An oven built of a single thickness of brick will work well, but the
  extra mass and strength gained by a simply applied 2-inch layer of
  concrete makes all the difference."  Concrete, of course, puts it way
  OOP, but a layer of clay on the outside of the bricks should serve the
  same purpose, adding heat-retaining mass.

I was under the impression that concrete was invented by the Romans, and
that they even had a hydraulic concrete that hardened underwater...

	Tibor