Sunday, April 15, 2012

Pros and cons of fuels

Over Easter I fired fibre and brick kilns, with varying degrees of success.

The gas kiln is always easy, being gas, but brick and fuel kilns are a different matter. After about two years of experimenting with different fuels, I have decided to go back to diesel for the following reasons...sure, sump oil from a local garage is a free fuel source, its viscosity is also good, being mixed oils and transmission fluids. All of these burn extremely well and it gives a certain sheen to a glaze like only oil can, but it would have to be one of the most filthiest substances known to man. It's also quite possibly carcinogenic and turns the potter pitch black. After working with how clean gas is, I would prefer it to be like that for the brick kiln.

Which brings me to... vegetable oil mixes; the best one being a 50-50 mix of diesel plus canola oil from the local fish and chip shop. This also burns good and gives nice results,  but it has to be mixed and for best results put through a filter so as not to clog up (even slightly) the taps and burners. This can be time consuming, unless one enjoys this sort of thing.

The final straw for me was when it came to what was taking place in the fuel tank. I thought viscosity was the problem, then I saw the crap that came out of the tank! I had put clean canola oil in and it grew some sort of green algae slimy shite and a lot of it - that would slow down the flow somewhat. The sump oil had also left behind metallic dregs like small flakes and even little twists of metal, that looked like little snails, all packing down into a solid mass at the bottom of the tank. Sometimes being frugal doesn't always pay off,  but you have to try these things to see what does.

Preheating fire box .In this firing, I came in with desiel at about 300 degrees centergrade.

Once the diesel took hold I could control the rate of firing, just like the gas kiln, going from 300 C to 1300 C in around 8 hours.

Lunchtime in the best of company.

Silvery sunset.

Watching cone 8 go over, about to throw the salt in for one hour, just after sunset. As for atmosphere, it was going to be oxidised but with opening and closing the dampner and winding the fuel up till it looked like a dragon breathing through it (reduced),  or knocking the fuel back to slow it down a bit, creating a crystal-clear (oxidised) atmosphere inside, who knows what the outcome will be?
Interesting results and heaps of beautiful glaze tests to analyze.

Some of the better pots from the kiln, alongside cones 8, 9 & 10.

Diesel simplified things so much, no clogging of taps and burners, no oil slick all over my face, arms and legs, and the results were awesome. It's as close to using gas as I can get without using gas. It's worth the extra outlay to be problem-free.


Peter said...

I found that really interesting about the fuels. I sometimes think of switching to recycled oil or fish and chip shop oil, but haven't quite ever got that organized! Sometimes I even think about coal... (I know it has bad press these days with all the global warming fears, but it would be fantastic for salt glaze). We did a firing of the wood fired kiln yesterday after a long time away from it, and found it was easy and nice to fire with the new firebox, and mostly with our own wood too!

Bobo said...

Now THAT looks like a great lunch! Pizza, beer, and a cat, it might not get any better than that.

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