Slaked lime = The action of combining quicklime (CaO calcium oxide) and water
to form what is called a lime putty, or with the addition of more water, milk
of lime (whitewash). So, it does not matter how long you soak the lime in
water. The term used for soaking lime in water is called aging. The longer
you let the lime set in water the better, when it comes to mortar or
whitewash.

Basically what you start with is, calcium carbonate (CaCO3) this is what
oyster shells, chalk, and limestone are basically made of. You then take your
calcium carbonate and fire it in a kiln to around 1200 Fahrenheit this in
turn drives off all moisture within the calcium carbonate converting it to
calcium oxide (CaO). After you have converted your calcium carbonate to
calcium oxide you then have quicklime. When adding water to your quicklime
(slaking) your result is a fairly severe reaction. Your quicklime slurry
becomes very hot and begins to hiss and bubble as your quicklime (calcium
oxide) is being converted to calcium hydroxide Ca(OH)2. This is now what you
would call slaked lime, or as I stated earlier if you were to add more water
you would have milk of lime, whitewash, or what some folks call lime wash.

Hydrated lime on the other hand is the same as calcium hydroxide. The only
difference is when your slaking the lime, remember I said the reaction will
generate a lot of heat, so what happens is small amounts of water are added
to the quicklime and as the quicklime starts to react it will drive off some
of the water in the form of steam. So basically you are not completing the
slaking process, but only starting it.

If you are really interested in lime, might I suggest several books.

1) Building with Lime
2) Mortars and Cements
3) Preparations and Use of Lime Mortars

There are other books out there, but these were the only books that I could
think of off the top of my head. I hope this answers some questions. If not
you may contact me personally at  [log in to unmask]

Steve Elkins
Savannah, GA.