Yellow Limestone

Quoted text begins.Has anyone here ever made their own lime this way ?
End of quote.

< What does the slaking really do to the chemistry of the stone?

Kent,

Thanks for your entertaining story. It reminded me of a conversation I had with
a newly-arrived Polish immigrant, a tiler who was working with me on a building
site. I asked him what was the Polish word for stonemason - he thought about it
for a while, and answered "there is a Polish word, and the nearest translation
in English is 'convict'". Very appropriate, I thought.

In answer to your questions: I've made lime putty with stonemasonry apprentices
to show them the process. We take gravel-sized pieces of limestone and marble
and heat them in a kiln to 1100 deg C, allow it to cool and add the rock to
water in a metal drum, cool again, then store the slurry in a plastic drum.

We use 3 types of lime for small masonry building projects: powdered builders'
lime (hydrated lime); our home-made lime putty, and store-bought lime putty. I
do this so students can get a feel for the difference between them. We use
sand:lime 3:1; the difficult part of the exercise is getting students to
understand that even though their projects are dismantled after completion, lime
mortar is used not because it is a weak mortar, but because it is a versatile
building product. Modern masonry building technique demands fast-setting, strong
mortar not suited to natural stone. The only disadvantage with using lime mortar
for instruction is that it takes longer to dry out, probably why cement mortar
is so popular.

Burning, slaking and drying are elements of the lime cycle, more accurately
termed calcination, hydration and dehydration. Limestone (Calcium Carbonate) is
heated to drive off water and carbon dioxide, then slaked in water to produce
lime putty (slurry) and hydrated lime (powder). Lime mortar dries after bedding,
and absorbs carbon dioxide from the atmosphere in an attempt to turn back into
limestone.

The process is further discussed here (as well as in many other Internet
sources): http://www.saveheritage.com/limebss.htm

Simon