Today a truck full of bags of quicklime arrived at Casa Felix and we began the process of filling our lime pit to make lime putty. We will use this yoghurt-type stuff to make plaster in a couple of months when (notice I said when not if) the strawbale walls are completed.
First of all, limestone or chalk is quarried (in India they even use sea shells, after all limestone is essentially the accumulated corpses of billions of shells). Chemically, limestone is Calcium Carbonate. This material is burned to about 900 degrees C., which drives off carbon dioxide and water (not that there is a lot of water in limestone, but it happens), which creates quicklime – Calcium Oxide.
But this process can take a long time, and starts quickly and violently with the slaking, but then slows down. We keep the lime putty we have made – now like a runny yoghurt –
We'll use it to plaster the outside of the strawbale walls, where it will then set and turn back into calcium carbonate, giving us a strong, weatherproof, but breatheable protective layer.
OK, so back to the lime pit! The Romanian boys Petrus and Ilie had previously lined an old stone irrigation tank high up on the land with hydraulic lime mortar to seal it and stop any leaks. Paulo then made a cover for it from old roof beams and doors, to stop anyone falling in (although Magnus managed to part way through filling it up).
Magnus and Paulo then began filling the pit with water, ready to add the quicklime (you always add lime to water so it can dilute quickly and not get too hot – the other way around can get very hot and even risk an explosive reaction).
In terms of quantities: we have 1200 kgs of quicklime, and plan to add this to around 3500 kgs of water, giving a total mass of 4500 kgs or 4.5m3, which is the size of the tank. The lime is produced in Portugal and costs around 4.50 euros per 40kg sack (10 cents a kilo!).
Here's a couple of videos of the day's fun. Notice the prophetic moment 10 seconds into the first film where Magnus says “Don't step here because you might fall through” right on the spot where he later stepped and... fell through, when the panel snapped out of an old door and plunged him into the lime pit (with lime in it). Luckily, his ninja reflexes saved him, and he managed to avoid actually touching the lime – got some nasty scrapes on the leg and a banged wrist though. The elfen and safety Elf was not pleased (but managed to keep a straight face). Toast and tea made it better.
“Welcome to the Lime Pit”
“Slaking the Lime!”
“More Slaking from a safe Distance”