Hey are you guys using cinder blocks for the kiln you are showing the picture of?
I was told to stay away from both the cinderblocks and the regular fire place bricks for my salt kiln because of the high temperatures and the fact that the salt corodes the brick. (Well that and the fact that both fireplace blocks and cinder blocks can fail explosively under repeated heat stresses)
If you are using either cinder or fireplace bricks (rather then firebrick) what sort of temperatures have you managed to reach (if you have a pyrometer or even just a cone number)?
I'm curious because I've always wondered about the outdoor fireplace brick and was thinking of
trying to make something from them that would fire a lower cone of clay then what I currently use.
.... ummmm.... since I'm not sure if you have any formal pottery experience.... ummm.... I don't mean this to sound snobby but - if you need me to explain cone or pyrometer, please ask - I just realized I might be getting overly technical.
Nope, I get ya'. I haven't fired it up yet, because I haven't gotten a chance to really bury it. It 'is' cinderblock and standard brick... so it probably will explode in the future... but it's 100% backyard scrap so I'm happy. ;P
I'll be sure to let you know when I fire it up, though.
My mother was an enamelist and had three kilns. Prior to purchasing my propane foundry, I used her large one, a ceramics kiln, for casting brass and bronze. I plugged the small went hole in the front to help it get up to temperature faster. You can't leave copper alloys in a crucible as it cools. Some go through an expansion phase when solidifying which can crack the walls of a crucible. I once dumped a half full crucible of molten bronze on the basement floor to empty it when I was finished pouring molds. This was a mistake. Concrete is held together by calcium carbonate which contains a great deal of water of hydration. The concrete exploded which shot molten bronze all over the basement floor. Each of those little puddles then exploded creating even more hot spots. Eventually the metal landed on paper, or wood which caused dozens of little fires. So I had to go around with a bucket of water and put all of them out. After that I made a shallow sand box out of a piece of plywood and two by twos. I fill it with play sand and set anything hot in the middle of it. Concrete blocks will also likely explode when hot. Your best bet is to line your kiln with fire bricks or cast-able refractory. Cast-able refractory looks like concrete, but is stiffer. You can make sloped walls out of it. It fires like ceramic the first time your furnace/kiln/forge gets hot. If you are intent on using found materials, perhaps you can dig up some clay to use as a liner. Once dried, it ought to fire just like the cast-able refractory. These days I do all my casting outdoors, especially when I am melting brass alloys. If you melt brass indoors it distills off zinc which burns with a beautiful blue white flame forming zinc oxide smoke. In your lungs the zinc oxide reacts with water to form soluble zinc hydroxide which is rapidly absorbed into your blood stream. It's not really dangerous, but it will give you zinc fume fever which will prevent you from sleeping due to the shakes. I once had zinc fume fever and it kept me up half the night. I had to go into work late the next day. If you are melting scrap copper alloys, certain trace elements can be seriously toxic. Cadmium, lead, and beryllium for instance. So good ventilation is a must.