> Just athought,
> You mentioned that limestone is porous , what if there was
> heavy rain in those days, would this liquid plaster, as Petrie
> terms it , give it some protection from from this rain, maybe
> in their day the rain was more acidic than it is now .
Well, there is a hypothesis that the entire pyramid was painted red (Khafre?) which could contain sealant.
Also, granite is far less porous than limestone, and the lower 1/2 of Menkaure is coated with granite casings.
The mortar between the casings that remain at the base of G1 has been reported to be stronger than the limestone blocks themselves. This implies they're more dense, stronger, and perhaps moisture-proof. If the exposed surfaces of the blocks were not sealed with such mortar, then at least the seams BETWEEN the blocks were water tight which is all you'd need to keep water out of the main structure.
But I also think we need to consider whether there was a concern about making it tight from water (and gas?) that lies WITHIN the pyramid, e.g., in the passages and chambers, especially if we follow the line of thought that G1 might have been a water pump for the purposes of generating energy and/or providing a pressure head for water irrigation to support what Romer claims was upwards around 1.6 million people during the Old Kingdom (and who knows how many people were living around those things when they were actually built?!)