What is Quicklime?

Mary McMahon
Mary McMahon

Quicklime, more formally known as calcium oxide (CaO), is a caustic alkaline substance that is produced by heating limestone in specially designed kilns. There are a wide range of uses for this substance, ranging from mortar to flux, and it has been used by humans for centuries. Many companies produce and sell it, sometimes with specific chemical impurities that make it especially suitable to certain applications.

Quicklime was used in Mesoamerica to treat corn.
Quicklime was used in Mesoamerica to treat corn.

Humans have been aware of the steps needed to create quicklime for a very long time, and chemists believe that its generation may be one of the oldest chemical reactions known to man. People have certainly been using the material all over the world for thousands of years; in Mesoamerica, for example, people treated corn with it in a process known as nixtamalization, while in India, it was used in a mixture designed to waterproof boats. Today, quicklime is used in many industrial processes, some of which were developed hundreds of years ago.

Quicklime was used in India to waterproof boats.
Quicklime was used in India to waterproof boats.

Quicklime is also known as burnt lime, a reference to its manufacturing process, or simply lime. To make it, limestone (CaCO3) is broken up and shoveled into a kiln, which is heated to very high temperatures. The high temperatures release carbon dioxide (CO2) from the stone, turning it into calcium oxide. After it is cooled, the compound can be ground into a powder and packaged for sale.

Numerous things can impact the quality of the resulting material, ranging from the temperature of the kilns to natural impurities in the stone. Because limestone is a natural product, it can sometimes be hard to control these impurities; as a result, companies that produce quicklime tend to test their product regularly to ensure that is of high quality. The specialized kilns are also closely monitored to ensure that the limestone heats and cools at an appropriate rate.

Quicklime requires careful handling. As it sits, it can acquire carbon dioxide from the air, reverting to its original form. This means that it needs to be used quickly, especially once it has been mixed with water in a process known as slaking. Lime is also extremely caustic; it can burn the skin and cause other damages. When used responsibly, it can be immensely useful for things like mixing strong mortar, acting as a flux in smelting, and treating wastewater.

Quicklime is commonly used to make mortar, which is then utilized in a variety of construction projects.
Quicklime is commonly used to make mortar, which is then utilized in a variety of construction projects.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


What lime could be used to put in the old outhouse at the cabin?


When lime is mixed with water it gets hot. More lime than water causes a chemical reaction. The center of a small pile of lime when it is mixed with water the center can reach to temps like 1500 degrees. When handling it like I do, the mixture of sweat, lime and rubbing from the coveralls burns the skin. White vinegar neutralizes the lime as well. It stings like peroxide on a cut. Lime is not flammable. I actually ash my cigarettes in it all the time.

A big whiff of lime will leave you breathless. You will feel like gagging. As far as I know, it does not cause cancer but may leave burns through the moisture in your lungs. I also think that it can do some damage to sinus cavities. After being in it for like 20 or 30 years can cause silicosis I believe.


Please tell me the quantity of quicklime required in manufacturing of hydrated lime.


I purchased qucklime about 1990 to white wash field stone cellar, but never got around to it. It was kept in metal container, so is it still active, and if so, how do I dispose of it ?


We have a dead horse in an inaccessible part of our property. Could quicklime be used to dispose of the body/eliminate the smell? If yes to either of these, how?


can i make quicklime without using a kiln? And also can it be used as a component in cement?


I would like to know whether Quicklime is used as soil amendment. Is it used as soil amendment in India, and if so, in which crops and under what conditions. Thank you.


What can I slake a 50 lb bag of hotlime/quicklime in? A wooden trough has been suggested, Home Depot buckets or a metal garden trough/planter. I am making an art fresco and will store the lime in the basement for six months once the reaction is settled. Thanks! Cathy


yup. lime is used to dispose of dead bodies. ain't ya seen any good mob movies?


It's all right, but there are no chemical equations to show how to get materials such as flux or mortar.


Quicklime can be made by heating chalk on a stove

or even better,a bunsen burner. It has to be red hot

for a minimum of three minutes. Leave it it in a dry place to cool. Use it instantly or put it in a sealed,dry container. It will turn back to chalk if not stored like this.


where can I get small sample of quick lime for experimentation? I want to measure the heat generated amounts for various small samples helping my kid's science project.


We're doing this school project on lime/ quicklime/burnt lime or slaked lime...whatever you wish to call it .. got any fun facts a class of rowdy teenagers would apppreciate? Just something in the abc's of all this science stuff thanks :)

Oh and guess what there was a guy who killed himself making marmalade. I was sad but it made me laugh a little :)


quick cool fact: during the Terror of the French Revolution the tombs of kings (specifically at Saint Denis) were sacked and destroyed and they dumped the embalmed remains in quicklime.


Hello. I read that the bodies from the Wineville Chicken Coop Murders were disposed of using Quicklime. Is that possible? If so, does quicklime do that just mixed with water or did they use other chemicals?


Im planning a Science Fair project for school using Quicklime in a Steampower system. Is there any where that i can buy a bag of burnt lime?


Hello, Can I use quick lime to heat my home? thanks.


Ammonia was used for air conditioning what can be used instead of that? Thanks.


A company named ontech has combined this century-old knowledge with state-of-the-art packaging to create a revolutionary container that heats itself. I purchased a coffee beverage that, when turned upside down to push the button which breaks an inner-foil seal allowing water to mix with the quicklime, the darn thing heats itself to a seriously hot cup of coffee in mere minutes.

After reading your article, Wise Geek, it's apparent that this same substance is what generates the heat in those muscle-ache pads I get at Walgreens. Once they are opened (exposed to Oxygen), they heat up. Sounds like good 'ol lime at work.

I wonder if I'll vaporize myself by applying that heating pad while drinking a cup of the self-heated coffee?

~Westchaser - May 2008


good information. I have been researching how stone buildings were made and they kept referencing "quicklime" but never said where it came from or what it was...so the old mortars were basically burned limestone, sand, water, horsehair and a little mud...

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