I felt I should do some real work too, so I mixed three barrows of concrete, bent up some rebar into right angles, and filled the cores of my support blocks, using a couple of bars in each.It all looks pretty ugly inside at the moment. The rebar will tie the cores to the hearth slab, which will be the next thing to be poured. First I need to figure out the best way to hold the concrete in over those very uneven stones.
Sunday, 16 September 2007
Saturday, 8 September 2007
That's one of the blocks in the background, which got the hot end of my blowtorch for ten minutes. The spot I heated glowed red after a few minutes, then a satisfying yellow colour after ten minutes. I turned off the blowtorch after ten minutes and started my highly scientific test. The block was still cold on the back, so I tested to see how close I could put my thumb to the spot that I'd heated without screaming in pain. Told you this was scientific.
I could hold my thumb comfortably at about 4cm from the spot that was glowing yellow - this was about twenty seconds after I'd stopped the blow torch. The block was paler where it had been heated, although still pretty tough. I scraped a hole in the block, and the discolouration was only for the first mm or so.
I think these look promising - as insulation they'll never need to take this sort of direct heat, so my test was way over the top. They're clearly good insulators - I think I'll use these under the heath. I'm impressed that they're a recycled product themselves, which fits nicely into the ethos of my oven build.
The fire burned for about 3 hours (a lot of stuff to get rid of), then burned down overnight. The embers were still red and glowing after 6 hours, so those bricks got pretty hot. 24h later they were still too hot too touch, and were almost too hot to hold with my thick welding gloves on. The bricks survived fine - didn't seem any worse for wear after their cooking. That's a cooked one on the left - the one on the right is uncooked. I think they'll be fine for my doorway arch - the chopped off bit should allow the inner door to fit nice and tightly. And they're free!
Sunday, 2 September 2007
I had some help from a very enthusiastic three year old with the last few lumps of rubble (thanks Thomas!), but still had a fair bit left. No matter, simply bung it in the spaces around the concrete support pillars - I can use it to help support the hearth when I pour it.
I'll fill the last foot or so with more rubble once the mortar's set on the top stones. I'm pretty pleased with that for a first effort - the uneven levels on the walls will be taken care of when I pour the (level!) hearth. If anyone else asks me how I'm going to get the pizzas to fit in that little brick hole, I'm going to hit them.