Trying my hand at cascade pots

[Andrew F]

Hope all goes well. Look forward to the outcome

[vgarth]

Hooray! No cracks. (Thanks Velvet) I had a small crack in the base of one once it had dried; I put vinegar on it and smoothed it over. Looked after it had dried again, still faintly visible. Expecting failure, I put on more vinegar and smoothed again til no crack visible - I was pleasantly surprised it came through the bisque without the crack reappearing. Now have to see if it survives the glaze firing. Another week at least before I can do that. But very happy today anyway. Firing for myself is a very different thing to leaving work in my teacher's hands.

[fireworks]

Congratulations vgarth on the first firing of your pots. Looking forward to seeing the outcome of the glazing. Well done!

[vgarth]

Oh dear Fireworks, sorry if I've worded things badly - this is not my first firing by a long shot. Just that when my teacher fires, I don't have to think or worry about it. I have had this little kiln for years, and fired quite often, but I do have quite a failure rate, and I did expect the little crack I fixed with vinegar to re-open. I'm so glad it didn't.

I'm wondering about glazes, thinking of mixing up one my teacher gave me a recipe for. But at his place it's a reduction firing, so I don't know if it'll be worthwhile in oxidation. It's the glaze shown in anttal's posting of "My Val Garth Pots" Maybe I should just test-fire it on a small tile for a test.
cheers all, thanks for your interest. Val Garth

[vgarth]

Finally glazed those cascade pots, and now the kiln is on. I'm used to dipping when glazing, but that's no good for bonsai pots where one doesn't want the inside glazed, so I've usually been brushing. However, Horst Heinzelreiter showed on facebook how he pours glaze over the outside of his, so I decided to give that a try.

I did wax the base.

First I dipped the rim, to get a little up the inside, and to get a complete finish round the rim.

Then I placed the pot upside down over a tall spray can, (whatever was handy) with a bit of plastic wrap over the top of it to keep glaze out of the push-button area, and the whole lot standing in a shallow dish to catch the excess glaze.

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Pouring was messier than I'd hoped, (I keep trying not to waste glaze with spillage and so on) but it could have been worse. Most ran into the dish, and coverage of the sides was total except on one where I decided to leave gaps and put in a paler shade of the same base glaze. I used an iron glaze that should give a matt brown, maybe reddish in bits.

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Bottom shelf of loaded kiln - it's clear the glaze has sometimes gone in the wrong places, but that won't show when they are planted.

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And the top shelf, where you can see more bits of glaze inside.

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Really looking forward to opening . . .

[Andrew F]

Look forward to the outcome

[bonsaipotter]

Vgarth,
Thanks for the insight into your pottery world. It is so good to have the time to get absorbed into the job isn't it.
The pot geometry looks very good and the feet suit the overall design well. What sort of clay are you using and what temperature are you firing to. I have a few glaze recipes for cone 6 oxidation that I've formulated and tested - on my blog bonsaipotterycoy.blogspot.com From what I've been reading the firing cycle plays a big part in outcome too, ramps and soaks etc.
I'm still wrestling with the glaze application challenge. Running it on a spinning round pot sure looks easier than brushing.
I look forward to seeing the finished pots.

Cheers,

Happy Potter

[cre8ivbonsai]

[vgarth]

Well, it was a fairly disapointing firing result, and I've been trying to post comments and pictures for a few days, but keep having problems. Once I get enough text to fill this box, and the scroll arrows become active, I can't see what I'm typing, and the screen jumps and flickers. Don't know what I'm doing wrongly. I took out the pictures and saved a draft, but it was just as bad when I came back to it. After posting this I'm going to try again, without using the draft, and if it still doesn't cooperate, I'll try lots of short posts! Val Garth

[vgarth]

Clearly I've still got a lot to learn in the pottery field.

The kiln wouldn't reach stoneware temperature, (1280 degrees) and only got to 1240. I kept it on, hoping it would creep up, (as it used to) but after about another 8 hours, still at 1240 and turned it off.

I should be using cones, because I know it's not simply temperature, but a combination of time and temperature, and once I opened it the next day, I found that the extra 8 hours had been too long, and two glazes had run. (If I were to put cones in it, I'd not be able to see them anyway, it's all too low down. I did try in the past. Usually the pyrometre does ok.)

The first glaze that ran:

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And here's the pot after I lifted it off the shelf:

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And the skirt of glaze:

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[kcpoole]

Bummer
I take it you cannot grind it off and polish?

Ken

[vgarth]

Another glaze that ran was made on the same base as the one above. It's clearer, greener, looked lovely on the test tile I did.

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Also this glaze crazed badly, (and not attractively) showing that it did not fit the clay well.

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The other glaze I used, a matte reddish brown (iron) didn't seem to suffer from the extra time. It looks much the same as it did on its test tile, a bit redder.
There was another problem; I got little gaps in the glaze, making white spots, on the rims. I know I didn't drip wax onto the rims. I saw that they had a good cover of glaze. But I think I know what the problem was; because I poured glaze down the sides with the pots upside down, driplets dried in thick spots on the rims. I know in class if we had any thick spots like that, the teacher would advise us to rub them back gently once dry, to an even amount of glaze. I thought this was just because it was domestic ware, and dribbles would be unsightly. I suddenly know it was more than that - the over-thick glaze hasn't resulted in dribbles that are attractive on a bonsai pot, but in the glaze crawling away from the area. You live and learn.

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[Edward Scissorhand]

Hi Val, Just wandering, pardon my ignorance in pottery but why couldnt the kiln reach stoneware temperature?

[vgarth]

A further problem was that the bottom edges of even the better pots chipped as they contracted across the shelves. After picking them up and seeing the chipping, I recalled that in class, if ever I turned a sharp-edged foot ring on a cup or bowl, the teacher advised me to round it off with my thumb, saying sharp edges chip on the kiln shelves. And when prompted to in class, I always did it. But on my own, I didn't remember, and I thought the clean abrupt edges looked neat. Now that I've seen how they chip on the kiln shelf, I hope I'll remember to round them just slightly with my thumbs in future. (I'm starting to realise I must be a slow learner!)

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I did the usual sand-paper rub to get off the kiln-wash.

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Then I used a grinding wheel to smooth those chipped edges.

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And I tried to improve the glaze overruns, (hoping to salvalge those pots for my own use as training pots maybe), with the grinding wheel.
Not really very successful.

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And, it doesn't help if you don't hold the pot on the correct angle. While trying to get to one spot, I bumped the good side against an edge of the grinding wheel. Not even a training pot now!

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[vgarth]

So my final result is 5 pots, I guess usable but not as good as I'd been hoping, and 2 bits of rubbish.

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I have to do better next time. Maybe I just rush at things too much, I've got to be careful!
An unsatified Val Garth