Mortars, pestles and limes

March 26, 2009

Since readers seem to have liked my last post on preservation issues, here is another pet peeve of mine. I have worked for years with historic masonry and, like many architects who appreciate the best craftsmanship, have been consistently frustrated by the poor quality of re-pointing in many restorations. Even when the mortar used is a so-called “soft” or “historic” mix of Portland Cement, sand, and lime, the resulting mortar never looks as beautiful as the historic example that is being “replicated.” My colleagues in the field explained years ago that it was impossible to duplicate these natural lime and sand recipes because they were weak and would never stand up to modern codes. Besides, where was one going to get old fashioned slaked lime?

Well, after years of wandering in the wilderness, preservationists have a saviour. Virginia Limeworks is a company that believes in old fashioned construction techniques and has backed up their preference with products that perform beautifully and have been tested to modern standards. I have used their products and swear by them. Mix’n’Go is a premixed mortar containing only sand and natural lime. It is a mason’s dream, according to tradespeople I’ve talked to. The advantage to lime mortar is twofold: 1) the resulting mortar is completely breathable, just like the stone and brick it complements; and 2) the natural color of the sand stands out as in no other mortar mix. One never has to use a colorant or admixture. Simply get the local sand that the original masons used and combine it with lime for a beautiful wall.

Check out Virginia Limeworks when you do your next repointing project, or insist that your mason call them up. And if you are a purist, simply buy their natural lime and mix everything yourself. No need to slake the lime or grind the mortar with a pestle. Unless of course you want to risk burning your eyeballs out.

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