« Power from the Tap: Water Motors | Main | Heat Your Clothes, Not Your House »


Feed You can follow this conversation by subscribing to the comment feed for this post.



Very interesting article, I've always wondered about the various limekilns we see just about everywhere, and what their purpose and history is.

One minor correction: you say of quicklime, "It caught fire easily – sometimes too easily – and was used to make an early, high-intensity lamp for the stage – the original limelight."

Of course, quicklime is not flammable - if it were, it would be consumed in the kiln! A 'limelight' is created by heating calcium oxide to a very high temperature - via an external heat source, such as a flame - until the calcium oxide gives off bright light via incandescence. The quicklime does not - and cannot - burn.



Quicklime is non-flammable, but there is yet another substance named "lime" that this article didn't mention.

Over-burned lime (calcium carbide) releases acetylene when it gets wet. Acetylene is very flammable, and a lot of heat is evolved when lime is "slaked", so I could imagine a wagonload of lime catching fire spontaneously, if the limeburners had originally used too much fuel and conditions were humid.

This method of making acetylene is how blowtorches were fueled; the evolving gas would push down the level of water in the container, regulating the pressure automatically using gravity. It's a neat system, if not particularly efficient.



The CO2 emissions from the cement industry are not becaue they use so much power for the milling. It is the CO2 which is set free in the precalciner, exactly the same process as burning lime. For 1.6 tons of raw meal you get one ton of clinker. The remainder is mostly CO2 which leaves trough the stack. A cement plant which produces 10000 tons of clinker a day will release 6000 tons of CO2 . Depending on the fuel it will a bit more. The emissions caused energy consumption of the mills are marginal if you compare to this numbers.
Cement plants nowadays use large amount of secondary fuel. The burn all kinds of waste. As the temperature are so high, even some toxic fuel can be used.
By the ton modern cement plants are more energy efficient and the gas can be cleaned in several stages. First plants will generate electricity out of waste heat.
Also there are many types of cement not only Portland cement. Some have similar properties like the Roman cement.

Michael Gambill


A fascinating look at the historical significance of this technology. Understanding past advancements equips us to make informed decisions about today's technology. It is a point that I regularly make with my high school history students. Well done and thanks.



Loved this article. I am currently writing a masters thesis on lime kiln use in early settlement Saskatchewan - it was nice to see a concise and interesting write up on the traditions these homesteaders in Saskatchewan were drawing their knowledge and skill from. Thank you!



Thanks a lot for the article. This is a very interesting one, as it clearly shows that in the 'good old days' not everything was sustainable either. Especially note the 'toxic fumes' bits...

However, the footprint is still different. Just compare those relatively few kilns with the incredible numbers and area of industrial ruins and wasteland that we are leaving to our descendants. A shame.



Nice article.

As a variation:
In our sea-side village in Holland a kiln (one of many in the past)has remained that used shells as raw material; no limestone in this country.

Peter Dew


Presuming that slaking lime refers to adding water to the quick-lime to make hydrated lime or calcium hydroxide for mortar, is there a specific term for burning the limestone to make un-hydrated or quick-lime ? It doesn't seem right that they simply burnt or burned limestone, which I understand may have been a key industry based on salvaging it from ruins in Medieval and Renaissance Rome.



To Lindsapril - have you finished your thesis? If it has been defended could you tell us the title and which university library it's in?



To Lindsapril, I found your thesis and congratulations on a fine work.

eric koperek


CaCO3 (limestone or shells) + intense heat = CaO (quicklime) + 2CO2 (carbon dioxide gas, the fizz in soda pop or beer). Heating 1 pound of limestone rock in a large campfire yields 2/3 pound quicklime + 1/3 pound carbon dioxide gas. It is not necessary to build a kiln in order to burn limestone to make quicklime = burned lime = caustic lime = CaO. You can burn lime in piles on top of the ground. Start with a layer of fuel wood 5 feet wide and 8 inches thick. Add a 4-inch thick layer of limestone. Limestone rocks should be the size of your fist or an orange = not more than 4 inches in diameter. Alternate layers of lime and wood until pile is 5 feet high and as long as needed. Cover entire pile with firewood 1 foot thick. No limestone should be visible. Ignite pile and let burn until fuel is consumed. Let pile cool completely. Sift burned lime with window screening. Wear gloves, goggles, and dust mask. Good lime will crumble freely and pass screen. Bad lime (over-baked lime) and green lime (under-baked lime) stays in hard clumps and will not pass screen. Store good burned lime in water-tight barrels in a dry place until ready to use. Spread bad lime and green lime on agricultural fields to "sweeten" soil = increase pH = make soil more alkaline (less acidic). Burning lime with wood on top of the ground eliminates formation of "bad lime" = over-baked lime by keeping temperatures moderate. Surface burned lime yields about 75% good lime + 25% green lime (under-baked lime). Quicklime made in traditional stone kilns has lower yield: About 25% green lime + 50% good lime + 25% bad lime. For more information on old-fashioned agricultural technology, visit: www.agriculturesolutions.wordpress.com -- or -- www.worldagriculturesolutions.wordpress.com

eric koperek


Response to Joel (comment # 2 above): Calcium Carbide = CAC2 is NOT "over baked" lime! Calcium carbide was not invented until 1892. Calcium carbide is made from limestone and coke heated in an electric arc furnace at 2200 degrees Centigrade. These temperatures are NOT possible with common lime kilns or open fires. end comment.

Burned Lime vs. Agricultural Lime: It is not necessary to burn limestone rock in order to "sweeten" agricultural soils. Powdered agricultural limestone, chalk, or crushed shells work just as well and are much less costly. If possible, use dolomite limestone or dolomitic limestone as these rocks also contain substantial amounts of magnesium, a necessary component of plant chlorophyll. Rule-of-Thumb: Most agricultural soils east of the Mississippi River require 2 tons = 4,000 pounds of limestone per acre (1.5 ounces per square foot) to keep a slightly acidic soil pH of 6.5 to 6.8. Slightly acidic soils help plants absorb essential micronutrients. If limestone is not available or too costly, apply common wood ashes or agricultural charcoal at 4,000 pounds per acre (3 ounces per square foot). 2 pounds of wood ash or agricultural charcoal = 1 pound of powdered agricultural limestone. NOTE: Always mix agricultural charcoal with an equal volume of manure and compost for 30 days before application. Do not apply uncomposted charcoal to the soil or it will soak up nitrogen and your crops will be yellow and stunted.

Richard Rhodes


Thanks for your impressive work on this technical and somewhat difficult subject. Many people get this wrong and I find your article and research illuminating. I am sure others will value it as well.

Keep up the good work,

Richard Rhodes



The first photo in this post, shows a harbour marker to the north of Porthgain harbour, not a limekiln.

Beth Jabornik


A fascinating article. Thank you for publishing this. I am researching kilns in Australia.

Amy Roddey


This is a fascinating piece. I want to read everything else you have written and learn what you know about other subjects as well. Thank you for putting this together and sharing. I have three sons and I think I know what you mean.

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Your comment could not be posted. Error type:
Your comment has been saved. Comments are moderated and will not appear until approved by the author. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.


Post a comment

Comments are moderated, and will not appear until the author has approved them.

Your Information

(Name is required. Email address will not be displayed with the comment.)