How to Make Slaked Lime (Cal)

Slaked lime, or calcium hydroxide (Ca(OH)2), is a versatile chemical that hardens mortar and facilitated the Roman invention of cement. In Mesoamerica, the same chemical is known as "cal" when used to treat corn. Despite this rather impressive pedigree, however, slaked lime is also one of the easiest chemicals to produce at home. The key starting ingredient is quicklime (CaO), which is sold as a common soil amendment at gardening stores all across the country. It can also be produced by burning limestone or shells, but the process is somewhat labor intensive.

Things You'll Need

• Safety glasses
• Quicklime
• Water
• Heat-resistant glass beaker
• Spatula
• Stove

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Instructions

1. • 1

     Put on your safety glasses. Fill the heat-resistant beaker half full with two parts water to one part quicklime. Be sure to add the water first, as reversing the order could cause an explosion.

   • 2

     Stir the mixture with the spatula until there are no clumps. Let the quicklime and water react for at least 30 minutes. The reaction may produce enough heat to boil the water.

   • 3

     Place the beaker containing the slaked lime on your stove, and set the temperature to medium, unless you want a liquid solution.

   • 4

     Boil the solution until there is no water left in the beaker. (The water vapor produced is nontoxic.) Remove the beaker from the heat and let it cool. You should see a crust of white calcium hydroxide at the bottom of the container.