Latest electric firing 21/03/213

A few photos of pieces from Thursday's electric firing:

Jar or vase, approx 5 inches tall

Jar or vase (b)

Water dropper, approx 2.5 inches tall

Vase, approx 4 inches tall

Lidded container, approx 3 inches tall

Guinomi, approx 3 inches tall

Carved vase, approx 3.5 inches tall

Jar or vase, approx. 3 inches tall

Bottle vase, approx 4 inches tall

Cup, approx. 2.5 inches tall

Dancing vase, approx 3.5 inches tall

Dancing vase (b)

The vase in the last photo was fired three times, first in a wood kiln, then in the electric to cone 10. I wasn't completely satisfied with it, so I dipped the top third in my new oribe glaze and fired it again to cone 10. I like this piece much more now, and was surprised how well the glaze turned out, considering it was applied to stoneware!

Teacaddy decoration

I decorated a teacaddy this afternoon, kind of a spur-of-the-moment decision..sometimes the best things happen when you do something spontaneous. The brushwork is black slip over an orange background, I can't wait to see how this fires.

The handle was made from the pad of clay left after wiring off a piece form the wheel..simply scraped off and scrunched into a loop.

Making handles under the warm sun

The weather is up, down and all over the place at the moment. It was pouring down on Saturday, snowing on Sunday and first thing today, beautiful spring sunshine..now it looks like it might snow again!

I spent this morning trimming cups and putting some handles on espresso cups..very enjoyable it was too, with the Beatles on the radio and the sun streaming in through the window.

Here's an example with a new handle design I've not tried before. Is the handle too big for the cup? I'm not sure yet, I'll wait and see how it looks and feels after the glaze firing.

Spring is here .. almost.

The days are starting to feel distinctly warmer though the mornings are still uncomfortable..and the water coming out of the workshop tap is hand-numbingly freezing! So it's onwards and upwards, time to "gain momentum" as someone said on facebook.

11th March update: I spoke to soon, it's suddenly turned arctic with temperatures around 0 degrees, and the snow has returned yet again! It's been another hard winter for making pottery.

Black iron slip test result.

As planned, I electric-fired several different slips under two types of glaze to compare the results. Both the iron slips were a 50/50 mix of the oxide and a white slip. The black magnetite slip does indeed give off oxygen at cone 10 (in oxidation), perhaps slightly more than the red iron oxide! It certainly produces different kinds of bubbles in the shino..more of a honeycomb than open pinholes. The key difference is that the black magnetite slip stays a much darker shade of brown, and looks blacker under the shino glaze (top half ).

The black iron produces a very rich, dark brown under a transparent ash glaze (bottom half)

The red iron oxide (synthetic) produced a less dark brown, which looks reddish purple under the shino. The bubbles in the glaze seem to be smaller, although this is also affected by glaze thickness. It's worth noting that where the glaze is very thick near the top of the jar, there's rather alot of pin-holing going on over the bare clay too.

Interesting that the Masons black stain has come out a very similar shade of brown to the red iron oxide under the transparent glaze, but looks darker under the shino, very similar to the magnetite slip:

slip with 20% Masons black stain

The Masons stain has also bubbled a fair bit, though less than the magnetite. To my eye, an equal mix of black and red iron slips looks more like the red iron than the black:

Finally a couple of pieces I decorated using black and red slips:

Wine cup (magnetite slip outside, red iron oxide slip inside)

Sake cup (magnetite slip)

So what have I learned from all this? Magnetite slip seems to give a richer, darker colour under transparent ash glaze, but is harder to decorate with due to the larger particle size. To minimise bubbling and pinholing with either material under shino, the secret is very thin glaze application. (I'm also wondering if a heavily crawled shino may help in allowing trapped gases to escape around the glaze) Of course I've yet to try genuine black iron oxide, FeO .. but I don't know where I can buy it. Does anyone know of a good source in the UK?

Manor Stokes wood firing Feb 2013

Here are a few of my best pieces from the latest firing we unloaded on Wednesday this week. We had a beautiful mild, sunny day for the firing and a freezing, damp day for the unpacking.

Sake cup

Sake cup

Tea bowl, iron decoration with shino inside

Unglazed vase

Unglazed vase (b)

Unglazed vase (c)

Vase, unglazed outside, shino inside

Vase, unglazed outside, shino inside (b)

Jar or vase with shino glaze

Vase, approx 5 inches tall

Coffee mug, carbon-trap shino (b)

Vase, shino glaze, approx. 5 inches tall

Many thanks again to Sarah Villeneau, Penny Withers and everyone else on the team for their help in making the firing a success.

"Bronze" glaze effects

Recently I've been making some forms which were partially influenced by ancient artefacts such as burial urns. I thought a bronze-like finish would be ideal for some of them, but I'd never come across any suitable recipes, apart from manganese-based glazes, which I'm reluctant to use because of potential health hazards. By a complete coincidence, I fired a couple of pots yesterday in saggars, and lo and behold, the glazes came out heavily reduced and looking rather like bronze! Well, various shades of dark green, grey and purple, which reminded me of the patina one sees on some ancient bronze objects.

Tea or wine cup, 3.25 inches tall

Sake cup, approx. 3 inches tall

I also fired some pieces with the matt ochre-ash glaze in oxidation, and these came out quite strongly yellow in colour. This glaze is very much affected by depth of application. When thicker it can turn quite blue-green from the ash content, and where thinner it can be red-brown to black. This time the thickness was moderate and even, so the colour is a fairly solid yellow with a few dark brown areas where it has broken on ridges. The yellow does have a slight green tinge to it, which I think is because the ash in this glaze batch contains alot of pine. I'm interested in developing a glaze similar to Japanese Ki-Seto and this matt ochre recipe (which I have adapted slightly from John Jelf's original formula) comes reasonably close, especially in the way it develops red-brown "scorch" marks in places.

Vase with matt ochre ash glaze, 4 inches tall