swimmers... (lime putty tales continued...)

[Will Shotton <shottonmasonry@zzzzzzzzz>]

This is an educated guess since first hand experience of finding a stone 'swimming' in the middle of a castle's wall isn't on my resume.

My theory would be that these stones would be found in the middle of the wall (maybe infill masonry) nearer to or beneath grade. If, over the centuries, these substantial investments (castles/prominent buildings) were repaired with lime mortar re-pointing and major re-grouting of the interior portion of the walls then over the years much of the sand and lime would separate from each other and settle themselves into stratified layers near the foundation.

I often find old barn and house stone foundations where all of the original lime mortar is absent save for some of the original sand between the joints. The stones are for all intensive purposes drylaid now and I just point in the interior/exterior.

What the restorers might be finding is significant accumulations of lime which have absorbed enough of the surrounding moisture from the moisture laden foundations to create a perfect, centuries old lime putty. Its characteristics would be more like thick drywall putty with varying degrees of sand mixed in. When kept in constant contact with water and deprived of oxygen it will never dry out and lose its plastic qualities.

Up until the late 1800s farmers/masons would maintain a lime pit somewhere near an aggregate (limestone) source and burn the stone to produce quicklime. They then would slake the quicklime by adding water and  (watching the show) create lime putty. This pit would then be covered to prevent oxygen penetration and left anywhere from six months to three or more years before it was barrelled and shipped to building sites where it was pounded into washed sand by hand to make mortar.

An explanation or other theories of the elusive 'swimming stones' would be most interesting...any takers?

Will