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.

Saturday, April 7, 2012

A spot of maintenance

It's easier to repair a pyrometer in the daylight than in the middle of the night in the dark and pouring rain...

bits in pieces.

Hmmmm... blue cheese and chicken, mushroom pizza and ham cranberry [plum,apricot] cream cheese garlic,oregano etc pizza washed down with a good larger or two.

Early morning start up blending with the morning mist, reminiscent of a battle ground scene...

our sleepy hollow looking east, workshop center left.

A large goat lives on the bluff up behind the kilns, he seems to have a lot of leisure time on his hooves, where he sits for hours cross legged. This morning I have caught his attention.
works as good as new

Saturday, March 31, 2012

Slow and Steady

It's been a busy year so far. I tried but failed at using canola oil as a fuel for the brick salt-glazing kiln - viscosity issues - so not enough flow, but since it is a medium-sized kiln I had a go anyway.  It basically blew itself out, but no great loss that some work was damaged, as I'm still interested in the test tiles that are still in there. I have already mixed up a test fuel to fire up this weekend if the weather holds out.

I enjoyed firing up some large terracotta pots in the gas kiln. It's so good not having to mix some (sometimes filthy) fuels together, soooo easy, and also cheap as [efficient]

Spyhole on the gas kiln- 800 deg. celsius and cooling.

Bottom shelf of the 'crypt' (salt glaze kiln) plus test tiles and clay sheath [top left] to protect the probe from salt.

If only it was like this all the time!

Bursting, stony texture from local clay straight out of the ground.

When the sun hits these pots, they heat up like they're just  fresh from the kiln - the burnt caramel look is as pleasant on the eye as any glaze.

Like a painter who does portraits of people, I like to make portraits of great pots in three dimensions.

Tuesday, January 17, 2012

Rough and ready

A quick post on salt firing...

In this photo I have cut a bottom shelf  and placed it on some props.I have also installed a crude bagwall.This time around I hope to not fire too much over 1300 deg c. because it plays havoc with my  kiln shelves making them hard as. If anyone out there has experienced cutting silicon carbide with a masonry blade you will know what I mean...The heat...the dust and these shelves aren't light either.
Tomorrow I will cut a third shelf and work on the chimney, kiln wash the shelves, etc and on next day - glazing and packing. Hopefully I'll be ready to fire up on the weekend, although I was planning a trip down the harbour to gather some cockle shells (for that nice wadding effect that everyone does) and a trip to a local forest for some pine needles for my raku firings. Good thing I'm not in any kind of a hurry... rough enough.