Masonry Magazine February 1987 Page. 63
an attempt to reduce soiling and thus maintenance costs. The rain screen principle, invented millennia ago, is now standard practice in modern cavity-wall construction. It is designed to allow moisture in the exterior cladding to escape into the cavity between inner and outer walls, eventually draining out through weep holes at the bottom. Thus, even if the outer cladding is sealed, moisture can escape.
Such technology cannot, however, be applied to heritage masonry construction, which does not employ the cavity wall design. In addition, silicone-based coatings are not only expensive, they also have a limited lifespan (five to seven years, average). A partial breakdown of the seal necessitates total re-coating. One is then locked into an expensive and, in the case of the Opera Centre, potentially disastrous cycle. In this case, silicone is clearly unsuitable. Martin Weaver, Heritage Canada, Ottawa, Ontario
Here is Mr. Merrigan's reply:
My article "Efflorescence: Cause and Control" dealt with the specific problem of efflorescence in modern construction. Mr. Greer is correct when he says sealants "may not be appropriate for use on all buildings." Any structure of historical bearing must be approached considering several factors that may not be of concern with new and modern buildings.
Before cleaning an historical masonry structure, careful analysis must be made of all factors, i.e., climate, age, type and condition of brick, type and condition of mortar, finished interiors, stains, efflorescence, sources of contaminants, etc. Only after all the elements are reviewed can a cleaning process be selected and a possible method of sealing (if any) may be chosen.
"Efflorescence: Cause and Control" was not intended to be construed as being for anything other than modern masonry buildings.
Michael Merrigan
Staff Engineer
Masonry Institute of America
Los Angeles, California
Editor:
With regard to the article on "Efflorescence" in the November/December 1986 issue, there is another effective integral water repellent compound called "Acme Shield" that is provided by our company. This is a one-product system for both block and mortar, thus eliminating dual inventory. Users of our product report it as being the most effective and low cost product on the market to impart water repellency and control efflorescence.
Data sheets and independent lab tests, including NCMA Test Reports, are available upon request.
Anthony F. Gulotta
Vice President, Marketing/Sales
Acme-Hardesty Co., Inc.
Jenkintown, Pennsylvania
Are Stone Masons an
Endangered Species?
Editor:
I very much enjoyed the article on efflorescence in the September/October, 1986 issue of Masonry. I mentioned it in our Christmas magazine On The Rocks. I have enclosed a copy. I have also enclosed a copy of the book I wrote, Kootenay Stone Centre's Guide to Beautiful Stonework. It is sad to see so many of the really good old-time stone masons retiring. I hope some of them will teach the younger generation their unique trade before they trade in their trowels for golf clubs. I would love to see more about stone masonry in your magazine.
Iris Bakken, President
Kootenay Stone Centre
Salmo, B.C., Canada
Road America
If you don't recognize either the driver or the car, that's MCAA Immediate Past President W. C. Dentinger, Jr. racing his 1955 Triumph TR3 at the Road America in the Vintage Group of the Sports Car Club of America's Kettle Moraine Midwest Regional Finals held recently in Wisconsin (Masonry Sept./Oct., 1986, page 30). Bill's car was the oldest in the 50-mile race, finishing first in the Sports Production Cars Under 2 Liters Class and second overall. Bill and his wife Shirley are both antique car racing buffs.
Letters to the Editor
Masonry invites letters to the editor. The subject matter may address articles or topics that have appeared in the magazine or which might be of interest to Masonry readers. All letters received by Masonry are deemed submissions for publication unless otherwise stated, and are subject to editing for style, grammar and limitations of space.
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MASONRY-JANUARY/FEBRUARY, 1987 63