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slaking-lime
You may be interested in following the process through from beginning to end – although you may not want to burn your own limestone, you may want to slake quicklime.
If you are able to do it, you will save money, but it can be dangerous,
and you may not be too popular with the neighbours, as it gives off lots of fumes.
It’s difficult for the public to buy quicklime, as it’s dangerous.
If you are thinking of slaking your own lime, read about the Health and safety aspects of it.
Quicklime is more dangerous than putty, as it is in powder form which can blow around, and putty is mostly water, which dilutes and turns the thirsty quicklime to calcium hydroxide. Mortar and plaster is less hazardous still, but we still advise using goggles as it can burn if it gets into your eye.
Do it in a very well-ventilated place, preferably outdoors.
If you do buy quicklime, it’s probably better to ask for powder and not small lumps. We have found small unburnt limestone pebbles in the middle of lumps when we’ve come to slake them, and have had to pick them out of mortars and plasters later.
Don’t store quicklime – slake and store lime putty. Lime putty gets better with age, but quicklime could begin to slake itself from moisture in the air (and then it could actually start to take
CO2 from the air and start to become calcium carbonate again!), and become useless.
To slake it
In a large metal container, (an old bath is ideal – nothing plastic though, as the heat generated by the reaction will melt it)
make sure the bath is stable (by wedging it with bricks etc.) and of
course that the plug is in or the hole filled,
add one part quicklime to three parts water.
Always add quicklime to water, and NEVER water to quicklime, as it will spit, and can be very dangerous.
There will be a violent chemical reaction with heat given off. You can test a small amount in a metal
bucket first. If the reaction is sluggish, you can use
hot water, although we’ve never found any quicklime to react sluggishly – quite the opposite in fact.
Temperatures over 100°C are achieved – water boils, lots of steam given off – and there will be some quicklime in the steam, so best not breathe it.
Wear a face mask and goggles.
If the reaction is sluggish, or the mix is too wet, it probably needs more quicklime
Rake continuously until all lumps are removed. Rake backwards and forwards with an old rake. When the bubbling stops and there are no more lumps, cover with an old board with bricks on top, and go back to it to rake it again after an hour, and then again an hour after that.
Then cool, shovel the putty into plastic buckets (with lids to stop surface water evaporating). Lime putty generates water that rises to the top when it cools. Make sure this layer of water is retained in the bucket before you put the lid on. If there is no film of water, add some.
Leave the putty for at least 3 months – it will generate its own lime water on the surface. Putty must not be exposed to air.
The longer you leave the putty, the better it will be, and it will ensure that absolutely all the quicklime is slaked.
Store in a frost-free place.
Lime putty will store forever, as long as there is a layer of water at the top, with a lid.
If you have the facilities to slake your own, it will be cheaper, because putty is mostly water.
There is more information on the site detailing the economics of the activity.
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