----- Original Message -----
From: "Mary Krugman" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, April 03, 2000 1:07 PM
Subject: Re: Beaver Board

water-glass (don't know what this is)

Water-glass is sodium silicate.   Was available in quart jars in grocery
stores
here until very recently (mid 1970s).   Used at home for preserving eggs
(you
immersed them in it for a day and they would keep for many weeks).

I learned to use it as an additive for water-proofing concrete when making
thin-shelled backyard fountains and pools.   It apparently forms salts
within the
concrete matrix, filling the spaces and preventing percolation of water.  We
used to put a cup or two in a wheelbarrow full of cement when casting a
pool.   When cured, the concrete would not absorb water, almost never formed
little crackettes, and in fact, drops of water would stand up proudly on its
surface.

Sodium silicate is still commonly used in ready-mix plants here during very
cold weather to hasten the setting time for concrete and prevent freezing.

cp