More limestone solution benchmarks. An 1890 study of dated limestone gravestones gave about 1 inch lost per 500 years. US Bureau of Standards roof cubes exposed about seven years showed oolitic limestone losing ~1 mm per century, compact crystalline limestone about a third less — Washington gets roughly 45 inches of rain a year. At Watts Bar Dam, boulders submerged 1912-13 and examined after 27 years predict about half an inch of dissolution per 25 years in moving river water. ⏳
Tombstones, Bureau of Standards cubes and Watts Bar boulders set limestone solution rates
Key facts
- An 1890 study of gravestones cut from solid unweathered limestone with a date inscribed on them gave a mean solution rate of about 1 in 500 years; applying that rate to about 25 inches (2 feet) of wall recession yields roughly 12,500 years, which the presenter calls a rough extrapolation.
- The US Bureau of Standards exposed 2-inch limestone cubes on the roof of its Washington building for about seven years; oolitic limestone lost a layer about 1 mm thick in 100 years, and compact crystalline limestone about one-third less.
- Washington receives about 45 inches of annual rainfall, so the video scales that cube result to a much faster rate for a wetter, flood-prone setting.
- At Watts Bar Dam on the Tennessee River, limestone boulders placed in a navigation dyke by the US Army Corps of Engineers in 1912-13 were examined after 27 years of submersion when a coffer dam was unwatered.
- Pure limestone dissolved 1/4 to 3/4 inch more than the impure laminae, and the paper predicts a rate of about 1/2 inch of dissolution in 25 years for limestone continually washed by free-moving river water.
- At that Watts Bar rate, 25 inches of recession would take about 1,250 years, a span the presenter doubts could apply at the Sphinx.
Sources
Clean a Gravestone Safely: Materials + Methodfarmersalmanac.com
How to clean a gravestone safely: get cemetery permission first, use only approved solutions (D/2 Biological Solution or plain water), soft brushes only, ...
Cleaning Gravestones- How should it be done?stoneletters.com
Cleaning a gravestone must be undertaken with great care. Here I share some tips on how to clean a gravestone or headstone.
Gravestone Cleaning & Repairbullittcountyhistory.org
Use only those solutions recommended for the type stone being cleaned. Marble and Limestone. Water only. Non-ionic detergent, such as Photo-Flo (available ...
Cemetery Cleaning | Burial Cleanimgchicora.org
Use clean water. If the gravestone is particularly dirty, change your bucket of water frequently, so that you are not dipping your brush into a suspended ...
How to Clean a Headstone: Safe Methods by Materialmemorials.com
For routine cleaning, water and a soft brush are usually all you need. For tougher biological stains such as lichen, algae, or mildew, D/2 ...
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