I'm curious about some of the wondrous materials available today are able to repel liquid water but permit water vapor to pass through. I've heard that housewrap-type plastics accomplish this by being perforated with microscopic holes that are slightly too large for liquid water, but large enough for the vaporous form to pass through. I have no idea how silicate mineral paints do it, though.

Housewraps and paints are thin films, though. I'd like to learn about how such properties could be imparted to a masonry unit like a compressed earth block. Could you cast such a block with a mixture of soil and some additive that would grant this kind of water repellency but allow water vapor to pass though?

  • $\begingroup$ Is liquid water molecule any larger than a steam molecule? Isn't there rather some trick with hydrogenium bonds? $\endgroup$ – Tomáš Zato - Reinstate Monica Aug 30 '14 at 16:32

The answer turned out to be waterglass. That's the carrier for silicate mineral paints.

  • 2
    $\begingroup$ I appreciate it that you took the time to write an answer yourself, but could you please elaborate so that the next person who had this problem would find a solution here? $\endgroup$ – It's Over Dec 9 '15 at 15:40

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