Next question is, how thick is the layer of lime??

I used to work in the quarry part of a lime plant, about 30 years ago.

We blasted raw limestone into chunks small enough to load into Euclid trucks and haul to the crusher. Crushed rock was then stockpilied and then processed into white lime inside the plant.

I did not work in the plant itself, but do know that they used gas fired kilns and some water in the processing of the crushed limestone into white lime powder. Never did even ask how it was done.