Q: I have a housing lot with adobe soil that is 56 percent porous. Thus, I've been thinking about making adobe brick. What portions of material should I use? Is there any way to make the brick waterproof? Was water glass ever used for waterproofing adobe? Lee F. O'Brien Reno, Nev.
A: Soil with a clay content of 20 or 25 percent is used in the manufacture of sun-dried adobe bricks. The remainder of the soil content ideally is a sandy loam with no more than 2 percent soluble salt.
Waterproofing of the wet adobe mixture is achieved by the addition of emulsified asphalt. I have never heard of using water glass (sodium silicate) to waterproof adobe bricks.
Before I manufactured waterproof stabilized adobe bricks many years ago, I had the soil tested by a laboratory to determine its suitability for adobe.
That test also determined the amount of emulsified asphalt or bitumen required to stabilize and waterproof the brick. An adobe brick 4 inches thick, 12 inches wide, and 16 inches long contains about one cubic inch of solid asphalt, but the bitumen is thinly spread over the entire mass.
Whether you intend making adobes commercially or for your own use, verify the usability of the available soil first. Get in touch with an oil company that already is making emulsified asphalt used in the process. Ask about cost and availability.
If you intend to build with adobes, you might be interested in ''The Adobe Book'' by John F. O'Connor, which describes the basics of adobe construction. Clothbound, the book costs $14.95 (the last we knew), and is available from William Gannon, 143 Sombrio Drive, Santa Fe, N.M. 87501.
As a further source of adobe information you may want to subscribe to the newspaper Adobe Today, PO Box 7460, Old Albuquerque Station, Albuquerque, N.M. 87194.
Before getting into the business of manufacturing adobe brick, thoroughly study all the angles, including your local weather, sales prospects, and manufacturing methods. You might even visit some other manufacturers.