Our New Intern from Korea

We have a new intern working with us this January. Our visitor is Ms. Kang from Korea. She has come here to experience our sustainable approach to life and our ceramic work.

We have been working together crushing and grinding porcelain clay body and glazes from local rocks, throwing pots, working in the vegetable garden growing our food, cooking the food that we harvest and doing a little bit of sightseeing as well. The three of us have been doing some tourist activities together, like a trip to Sydney with a ferry ride on the harbour, and a trip to the local National Park and the south coast beaches.

Ms. Kang has been learning to use our foot-powered ‘Leach-style’ kick wheels.  We have just finished making sufficient clay work today to fill the solar powered electric kiln for a bisque firing. Last week we calcined some local white granite rocks, to make our local blue celadon/guan glaze.

Pretty-much life as usual, but with a hard-working and dedicated student-guest.

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Update on our solar powered car – driving on sunshine.

We have had our new PHEV electric car for three weeks now and have just passed the 1000 km mark. I have chosen to drive it in hybrid mode to get the petrol engine run in a bit before the first service.

The first 1000 kms in a new petrol engine tend to involve a bit of wearing in of some metal parts that rub together. So it is good practice to change the oil and flush out all the iron filings that would cause some unnecessary wear  if left in the oil for a longer period.

Consequently, I have been testing the car out in ‘hybrid’ mode as well as in ‘sports’ mode, which involves running the petrol engine at higher revs for short periods of time. This is thought to get a better result during the ‘running-in period, than just driving the car gently for the whole time.

So we have reached the first 1050 kms and we haven’t used half the fuel tank yet!

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This engine is very efficient and the makers claim it can achieve just over 1000 kms on a tank of fuel.

The cars computer is telling me that we still have 524 kms of fuel left in the tank and we have already done 1050. At this rate we will be getting over 2,000 kms to a tank full of petrol.  I can see us only buying petrol once ever 6 weeks at this rate. It’s quite an eye opener to experience this level of fuel economy.

Not the elephant in the room, but the EV panel on the roof in this case, is the sunshine that has powered about half of our driving. After the car has been serviced for the first time, I will be choosing to drive more in fully electric mode and less in hybrid, and definitely a lot less, if ever in ‘sports’ mode. I can see us getting 2500 kms occasionally to a full tank of fuel at some stage in the future. If we log up 10,000 kms in a year, that will mean going to the petrol station just once every 3 months.

I have worked hard to get us into this position. I’m really enjoying being here now!

 

Solar fired electric kiln, reduction glaze firing

We have fired the solar-powered electric kiln to stoneware in reduction for the first time.

This all happened a few weeks ago, but I got distracted by the arrival of the new electric car, so I’m a bit behind in writing all this up.

The kiln worked perfectly, just as I had hoped. No problems at all. I had it packed with domestic sized items, cups and bowls, plus a few clay and glaze tests to see how things worked. Plus a spread of cones to see the temperature variations throughout the setting. This is only the first attempt at a reduced stoneware firing in this kiln, so it is new territory for me. I will need to test out the many options available to me to get the most efficient firing time with the best results, using the least amount of gas for the reduction, while achieving the best reduced colour.

I decided to try a fast firing, just to check out how fast the kiln can fire. It took 3 1/2 hours to get the 1,000oC and then I set up the pilot burners to start the reduction atmosphere. The burners clipped into their mountings easily. I was careful because the kiln was quite hot already at this stage in the firing. I made the mounting so that  one simple bolt can be slid into a hole like a pin, and the mounting is secure.

The burners lit easily off the kilns heat, I didn’t have time to click on the lighter to get them started. I had built a few different sized flue holes in 3 separate damper tiles. I had made a few tests at room temperature with the different sized flue holes.

A 12mm hole with a 5 kpa pressure. A 25mm hole with a 10 to 20 kpa gas pressure and a 32mm hole with a 20 to 35  kpa gas pressure. These settings were made at room temperature in a cold kiln, so I expected to have to make a decision based on the new volume of expanded gasses at the higher temperatures.

I chose the damper tile with the flue hole outlet in the top of the kiln of 25mm sq , as a starting point. Then adjusted the gas pressure to 10 kpa. This established a slight back pressure at the burner hole and a small flame at the flue exit. I also tried 12 and 15 kpa. This achieved what seemed to be a good back pressure and reduction atmosphere with a small flame at the spy hole as well, but the temperature was still climbing slowly. I decided after an hour of this to increase the gas flow and use the larger flue hole of 32mm Sq. This kept the same reduction atmosphere and back pressure, but increased the rate of temperature rise.

The kiln reached temperature in just over 2 hours and consumed 700 grams of gas at a cost of about $2.00. The electricity cost was nil, as we are totally solar here and I fired in the middle of the day, at the greatest solar productivity. But the cost foregone of lost sales of kilowatts to the grid was about $4.75, so a total theoretical firing cost of $6.75

Total firing time of 5.25 hours. A very fast firing. Not the best for good quality glaze quality, but I proved to my self that it could be done. I can now choose to fire any length of time slower than this.

The glaze result was OK. The reduced glaze colour of the rock glaze celadon could be richer and deeper, but it is excellent for 2 hours of reduction. The translucency of the porcelain was very good – considering the very short maturation time at high temperature of approximately just one hour. It was a very light pack, just to try out the kiln and all three sets of cones went over evenly at the top, middle and bottom shelves. Cone 10 right over = more or less 1300oC

The next firing will be a slower one.

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