Monday, 17 February 2025

Water swollen wooden wedges for splitting stone, a myth?


We have all heard of splitting stones by inserting dry wooden wedges into cracks and then soaking them. But I can't find any examples of it actually being tried. Literature searches give me these results:

"The use of wooden wedges and hydraulic expansion to split stone occupies a nebulous position between historical anecdote and mechanical plausibility. While physics principles and traditional narratives support its feasibility, the absence of contemporary demonstrations or archaeological incontrovertible evidence leaves the method in the realm of theoretical speculation."

"No experimental or quantitative data exists for the specific use of water-swollen wooden wedges in splitting stone.
The hypothesis that water-swollen wooden wedges were used as a stone-splitting technique is archaeologically plausible but lacks modern experimental support."

"while the theoretical framework and related experimental studies provide a basis for understanding the mechanics of wetting and splitting, the absence of specific practical demonstrations leaves a gap in empirical validation of this method."


So is it a myth or was it actually used? 

Roger Rowell claims to have seen the technique used in Egyptian quarries:

On a trip to Egypt in 2001, the author saw the evidence first hand. On the edge of a shear granite cliff, holes about 15 cm long, 5 cm wide and 10 cm deep had been chiseled into the rock. Dry wooden wedges the size of the cavities were driven into these holes. Water was then poured onto the dry wood and allowed to swell. The swelling pressure caused the granite to split down the chain of holes resulting in a giant obelisk or other large building blocks. 

Further citations are provided in: Nishiyama, Yoshiharu. (2023). Thermodynamics of the swelling work of wood and non-ionic polysaccharides: A revisit. Carbohydrate Polymers. 320. 121227. 10.1016/j.carbpol.2023.121227. 

A quite demonstrative example is the splitting of granite rocks by the swelling power of wooden wedges inserted in small chiseled holes as was witnessed by Rowell (2012) for which many authors assert the use of such methods in ancient Egypt (Eder, Schäffner, Burgert, & Fratzl, 2020;Katz, 1917), though the historical veracity seems controversial (Harrell & Storemyr, 2009).

Harrell & Storemyr, 2009 are quite clear:

A fiction often repeated in the popular archeological literature is that the wedge holes were cut for wooden wedges which, when wetted, would expand and so split the rock. In reality, this cannot work for the sizes, shapes, spacings, and often inclined orientations of wedge holes found in ancient hardstone quarries. Wooden wedges have been successfully employed in some modern hardstone quarries, but these require different kinds of wedge holes. (Harrell & Storemyr, 2009)



El-Sehily, B.M.. (2016). Fracture Mechanics in Ancient Egypt. Procedia Structural Integrity. 2. 2921-2928. 10.1016/j.prostr.2016.06.365.  provides details of a trial using swollen wooden wedges, to crack the rock blows were then applied to the stressed rock.

No comments:

Post a Comment

Comments welcome on fresh posts - you just need a Google account to do so.