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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    I had to look after the kids this weekend, so I used it as an opportunity to have a dry run with the bricks. I made a simple rectangle form, but that was a mistake as you need a handle to lever the form off the clay. There's also an ideal texture. Too soft and it slumps when the form is taken off. Too hard and it doesn't fill the corners. The bricks we made were a bit rustic, but I'll do better when I'm on my own.
    The clay shrinks quite a lot. One of the bricks has quite a crack in it. I wonder how much aggregate you can mix with it?
    • CommentAuthordickster
    • CommentTimeMay 25th 2018
    Just reading a great 1956 book on ceramics. The man says firing the same clay to the same temperature, but 1. for 12 hours, 2. for 14 hours, leaves shrinkage for 1. 12%, 2. 8%. Showing that time taken has a big impact on shrinkage (and cracking). All to do with them crystals, y'know.
    Drying the bricks coincided with last weekend's very hot weather, so the rapid drying may have been the cause of the crack. I suppose if it all shrank at the same rate, and there was nothing to prevent the shrinkage (such as if it was plaster on a wall), there ought not to be cracks. Next time I'll dry it more slowly indoors, and on a bed of sand so that there is no resistance where it touches whatever it is resting on.
    In case anybody is interested, here are the bricks. They turned out really well. There are a few cracks that coincide with the cracks in the clay, but I think if I had properly consolidated it (I was with the kids), it would have turned out fine. They are a lovely colour.
      Bricks small.jpg
    I really like the colour, well done sir.
    Posted By: ComeOnPilgrimIn case anybody is interested, here are the bricks. They turned out really well.

    So are you now going to make enough to build your garage as stated earlier - or just do enough for that new BBQ
    I think the plinth for the garage is the next step, rather than a whole garage. I'll make the rest out of hempcrete. I now need to work out how to make a kiln to fire then to the right temperature.
    I think you will be amazed at the amount of wood or other energy required to get a smallish kiln up to and holding firing temperature for bricks. Traditional kiln type bread ovens became the fashion here a while ago and most people stopped using them complaining about the amount of wood needed to bake a couple of loaves.
    I'm sure. I used a pizza oven in Italy and took a lot of fuel to get it to a few hundred degrees. I suppose containing and insulating the heat somehow would help.
    Posted By: ComeOnPilgrimI suppose containing and insulating the heat somehow would help.

    Without a lot of insulation a small kiln for bricks would IMO be a non starter. I suppose you could do the usual calculation of heat loss used for walls to get the u value to work out the heat demand to maintain a temperature. I don't know if the standard calculations hold true when the delta temp is over 1000deg as opposed to the usual 20 or so, but it might give you an idea.

    You can get special insulation for kilns - a sort of wool, not unlike glass fiber. Google kiln insulation.
    • CommentAuthormuddy
    • CommentTimeJul 8th 2018
    They look proper hand made, well done!
    I suggest you personalise them by impressing your initials and an obvious thumb print. The old roofing tiles here often have animal prints, bricks less so.
    When you design the kiln you want to make the flame path long and horizontal before it gets to the flue. To get to 1000 centigrade is fairly easy and you won't need high spec refractory insulation. You may get away with a cob mix as you are unlikely to be using the kiln many times. Old pallets would make a good fuel.
    With luck your bricks are drying in this hot weather already.
    • CommentAuthordickster
    • CommentTimeJul 9th 2018
    So I fired my kiln bricks a few weeks ago. Around 1/3rd survived intact, 1/3rd cracked into two, 1/3rd into 3 parts. Not so disastrous as they are simply laid flat on each other. They broke because I used too much sand 1:2 clay:sand and stacked them as you would a karate chop block, so very easily stressed to crack. I felt it more important that the bricks were fired all the way through and are weather proof(ish).

    At least I still have a usable kiln (just not so pretty)

    Used two days worth of wood collecting, fired in earnest over 3-4 hours.

    Nice bricks, Mr Pilgrim!
    Thanks @dickster! How do your bricks look? I'd be very interested to see how they turned out. Will you post a picture?
    • CommentAuthordickster
    • CommentTimeJul 20th 2018
    Found some pics, here are the kiln bricks and kiln top pre firing, not so pretty now!

    I used clay with little or no iron in it, hoping that the lack of iron will allow the kiln to survive high temperatures (iron acts as a flux) whereas the pots made with red clay (iron rich) should vitrify if desired.

    Remarkably, the inner dome (4:3 clay sand) survived the firing "intact" (broken into 3 parts pre firing, clumsy boy), but the outer freestanding 3 part hemisphere 1:2 mix was far too weak and broke up as the kiln collapsed into the firing trench overnight. Joy!

    Very luckily, I can simply lay these broken outers igloo style against the inner dome, so all, at the moment is good, but of course, I haven't used the kiln in anger yet (busy making pots).
    • CommentAuthordickster
    • CommentTimeJul 20th 2018
    Here's the other pic. Forgot to say bricks stayed almost the same colour after firing and don't turn back into clay when wet!
    That's beautiful dickster! What are you going to use the kiln for, now the bricks are fired?
    • CommentAuthordickster
    • CommentTimeJul 23rd 2018
    Hi Pilgrim,

    I have two aims, one is to make an iron knife from scratch without use of any modern tools and materials, so I need pots to keep things in and will also use the kiln to make charcoal. The idea of using bricks for the kiln is so that it is portable and can be kept in my neolithic shed out of harm's way from rain and frost.

    The other is that the clays in our area range from sandy coarse to absolutely fine as fine can be, so later on will use kiln for making lovely pots that I don't need.

    Primitive Technology on Youtube is doing much the same thing, but started well before me and is a great inspiration, providing a great many tips as to what to do.
    • CommentAuthordickster
    • CommentTimeJul 26th 2018
    • CommentAuthordickster
    • CommentTimeJul 26th 2018
    and after
    • CommentTimeJul 26th 2018
    Remarkable the way the bricks have pulled together when fired! :)
    • CommentAuthordickster
    • CommentTimeJul 26th 2018
    Yeah, forgot to say disassembled, reassembled!
    • CommentAuthortheforge
    • CommentTimeAug 10th 2018 edited
    We made around 1500 bricks on site from clay we dug from our garden with help and advice from Tony Mugridge.

    A couple of things we learnt in the process:

    i. Put the mound onto a board, this makes hacking the brick out and turning easier/possible!
    ii. Use well dried sand to lubricate the mould/board for each brick.
    iii. Pallet wood burns well with a high calorific value and achieves/maintains a better kiln temperature than logs.
    iv. Expect a high percentage of wastage using a ‘traditional’ clamp. Ours had a y configuration ‘fire box’.
      Clamp 2.jpg
      Fired Bricks.jpg
    Wow, those are cool! I love the frogs. Where did you make these?
    • CommentAuthortheforge
    • CommentTimeAug 10th 2018
    We made them all on site in our gardens and workshops attached to our forge. Kilns/clamps were built as far from our thatch as possible!
    • CommentAuthordickster
    • CommentTimeAug 14th 2018
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