Sand Castle Kiln

This kiln grew out of an experiment I played around with years ago with casting lead into a rigidised sand mould. I remembered that the sand went pretty hard and that it took the heat of molten lead. So this year (2009), to coincide with another ASP Guy Fawkes event I decided to have a go and build a sand castle kiln. My choice of materials was silica sand and bentonite. I did a few experiments first to figure out roughly how much bentonite I should be adding and came to a 15% ballpark.
On the day this meant mixing 50 kg of sand with about 6 handfuls of bentonite – a very precise and calibrated handful measure. The fabrication started with borrowing a few left over scoria rocks from Peter Lange’s kiln and using them as a foundation. Next a cardboard tube was used as a flame tunnel for the gas burner, covered with a layer of compacted sand and a foundation for the walls was bedded into the rocks.
The rest of the construction was made using sand pressed into a small, wooden brick shaped mould and each brick mortared with a sloppy sand mixture. This building method offered huge flexibility and the bricks were surprisingly rigid. My most useful tool was a sharp fish slice I used to cut the bricks into the various shapes I needed. At the top I decided to use some beer bottle in the hope of creating flame cannons latter.
I finished the kiln just as the first guests were arriving for the evening’s entertainment. The gas burner was installed and off the kiln went. There was a pot inside the kiln – a hapless victim that I pilfered from the abandoned pot table and so I did start the flame off a bit gently. Peter couldn’t resist adding a few chemicals to the flame and the most spectacular was again the copper compounds. Then, getting bored and curious to see if the kiln would crack and fall over I let rip with the burner. Nothing. The kiln belched flame as expected, but no disintegration – although a few, initially alarming, cracks appeared nothing moved. I tried blocking the flame from coming out the top to see if the flames would come out the bottles (after I had popped their bottoms out) but no luck. I think the kiln was too wet at the top and not hot enough. Still, the possibilities with this type of kiln, it’s ease of making and different methods that would be possible and the fact that after it is all over the whole thing will just disintegrate in the next shower of rain makes it an interesting idea to experiment further with.