Monday, November 20, 2017

Open Studio, Fish, Firings, Flops and Fun!

We were recently part of a local craft day and had our place open to the public with me demonstrating on the wheel, whilst Laura talked with people in our gallery. We had a busy few weeks getting work ready for the day, and Laura  painted some really lovely imaginary fish. Most of the fish were designed to hang on the wall, but I made little wooden stands for some of the others.

Sadly we may have only had 25 people through in total, so sales were a mug, a small bowl, and a card, which was a bit of a disappointment, but we are thankful to those who visited and we have got the place well stocked up for the summer season!

I had intended having some new porcelain paperweights for the open day, but only 2 of the 11 paper weights enjoyed their glaze firing... the remaining 9 were either under fired, over fired, or just plain stubborn and would not grow crystals! It was a complete contrast to the excellent firing I had the time before!

I contemplated trying to get another kiln of crystalline pots fired before the open day, but was too short of time... so had to do what the sign a the end of our street says...and Stop!

Instead I glazed a kiln load of 2 large, kiln filling pots and a medium sized one as I was desperate for new work to go to the Potter's Co-op for a window display that we were scheduled to have in the days running up to the open studio here.

 The jug, or pitcher, on the left is about 19 and a half inches high (49.5cm).

I used a Cone 3 glaze of my own, that I had tested on something small a few years before, but had never put on anything large. I was delighted by the result. The glaze is an alkaline copper blue and it was nice to see the colour variation where the glaze was thick or thin.

Laura snapped this photo of the Co-op window display on her phone.

Once the Open Day was over with, I spent the next week glazing pots for a firing of my wood fired kiln. The studio soon fills up with pots in various states of glazing, and it is quite a art finding enough space to fit everything.

 It is a relief to get the pots out of the studio, and the kiln loaded.

 The kiln fired really well, but....

I would love to report a great firing, but it wasn't... I got things too hot! I over fired many of the pots due to a series of errors and a poor decision on my part, so I lost almost everything that was copper red, and some celadon pots were very unattractive.

In spite of all that, there were some gems!

These small porcelain bottles are probably my favourite things from the firing.

 A shino jar.

 A 6 cup coffee pot (or teapot if you would rather!)

 A tea pot. The handle was made up from three tubes that were thrown on the potter's wheel, then split in half.

Shino seems very forgiving, and can cope with a wide range of temperature. This is a spoon organiser.

 And a tiny 3 inch high jug (7.6cm)

 I like this urn. It isn't quite the colour I intended, but it is dignified and peaceful. The lid was quite difficult to make, as it has to fit inside and outside the pot.

We were delighted to have a visit from a Sarah, who is a Christchurch potter. She spent 4 days working away in my studio with me, and it was nice to have company in the studio and 2 wheels going at the same time.

I am busy getting more work ready to fire in the wood fired kiln. The unusual looking thing on the right of this photo is a porcelain candlestick. I rather enjoyed making it, and hope to develop the idea further and make a candelabra for several candles.

Monday, October 2, 2017

Porcelain Paperweights. One important step remains... Hammer and Chisel!

A scary, but unavoidable, part of making a pot with a crystalline glaze is separating it from the little ring of porcelain and the glaze catching saucer. I was a bit anxious about the paperweights as their round shape does its best to deliver the maximum amount of run off glaze right to where the porcelain ring is joined onto the paperweight, and there was a chance that glaze would penetrate the join and glue everything together.

Some crystalline glazers favour using a gas burner with a very thin flame to work around the join, but I find that a sharp chisel and a hammer does the job quite well.

I like to tap right round the join quite gently and try to form a little scratch or fault line in the run off glaze with the chisel as I go. I can generally give a series of smart taps after this, and the ring will pop off.

 The run off glaze leaves a sharp edge and this needs to be ground off.

Wet grinding with an abrasive disk fitted to the wheel head is a great time saver.

I finish off around the edge by hand with a high tech sharpening "stone" that is designed for sharpening chisels.

The paperweights really come to life in sunlight. The crystals scintillate in spectacular fashion, and their intricate structures become more apparent.

  1 percent cobalt oxide gives both blue and purple in this glaze.

1.5 percent nickel oxide gives Prussian blue crystals and a orange glaze around them. Amazing details in this glaze, you could spend hours with a magnifying glass exploring the stars and flowers!

The star shapes in the centre of these crystalline structures are rather fine!

Copper carbonate with just a trace of iron oxide gives golden crystals floating on a green glaze.

A Crystalline glaze recipe

I have played with several crystalline glazes over the past few years, but the one I use most often at cone 9 - 10 with the porcelain clay that I have is as follows;

Frit 4110  47
Zinc oxide  27 (you can use regular zinc oxide, but you may find calcined zinc makes the glaze somewhat easier to apply).
Silica  24
China Clay 0.5
Bentonite  2

+ Titanium dioxide  3 (The titanium is left out altogether if nickel oxide is used for colour, but is part of most other glazes in 2 - 5 percent)

To this you can add copper, cobalt, iron, manganese, or nickel, by themselves or in mixtures with interesting results. Rutile and ilimenite also extend the range of possibilities. You should experiment. The glaze should be applied thickly.

The way that the kiln is fired makes a profound difference as to how crystalline glazes turn out. Temperature and time are used like an artist's paint brush to create crystals of different sizes and shapes.

A way to start with the glaze base I have given here would be to fire as follows.

Fire quickly to Cone 9 fully down and Cone 10 starting to bend --using cones-- not just relying on controllers and gadgets! If possible the kiln should climb at at least 125 Celsius (257 F) per hour for the last hour or two (more is better). Let the temperature fall to about 1100 degrees (2012 F), and hold for 3 hours then switch the kiln off. 

If you follow that schedule you should get crystals, maybe as big as an inch and a half in size.

*Note that great care must be taken to protect your kiln shelves from run off glaze. Crystalline glazed pots should have glaze catching bowls placed under them. If you don't know what those are, have a look back at my previous 2 posts.

Have Fun!