Shout and scream and jump up and down, then drink tea.

Arghhhhhhh!

I think I counted my chickens before they hatched. I have just unpacked my kiln this morning and have managed to salvage about 4 pots from it. The top is completely underfired and the bottom is over again. The middle was lovely but there wasn’t much of it.
What a job! Why do it? (OK I know why I do it really but at 9.30 this morning I wasn’t half so sure.) I unpacked it all, strewed it around the workshop, looked at it, looked some more, cried a bit, gnashed my teeth a bit, stomped my feet a bit (then realised this hurt my still sore knee too much) and then did the only two things possible, I made a cup of tea and started again.
After that decision was made it was oh so much easier to deal with, I think this time it was my fault for a) packing the bottom too tight and b) not having sorted out any fresh glaze tests. (Just mixed one up this afternoon.) The most annoying thing is that I think they were possibly the most well thrown pots and the best decorated that I’d ever made and I was so pleased with them.
It’s not very good for my sanity levels though, wreaking lots of work just before three pretty major events for me, I need to stop and think more I think.

These two plates at least came out well, and I am quite pleased with them.They were fun to decorate and I like mad birds.

And finally seeing as you lot are my equivalent of “phone a friend” what can I do to my glaze sort this? From what I can gather I need to make the glaze contract more while it is cooling. What will give me that? My brain is just going round in circles trying to decide what material is what and from reading the Potters Dictionary of Materials and Techniques almost in it’s entirity, it’s all muddled now. Any help gratefully received.
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11 Responses to Shout and scream and jump up and down, then drink tea.

  1. potterboy says:

    The bird plates are nice but that top jug is really fab.You don’t really say or show what happened to the top and bottom pots. Why do you say you need the glaze to contract more?

  2. Hannah says:

    The top is very underfired, the glaze is still matt. The bottom shelf has all shimmered/shivered, apparently according to my bible this is because the glaze on cooling shrinks at a different rate to the body and is under too much compression (I think that’s the gist of it.)When glazes craze it’s apparently because the glaze in under tension. I think that’s the right way round.The other option would I think be to make my glaze have a higher melt point maybe.

  3. Hannah says:

    The jug is beautiful but the glaze is merrily pinging off the rim as we speak.Arggggghhh!

  4. ang says:

    wow it sounds like you have some glaze testing ahead, are you using cones so you can tell the firing temp difference between the bottom and top? that would be a start to know exactly what you’re dealing with, after that i’d be looking at adding a frit to your glaze mix and testing the base flexibility. Leaving more space around plates / shelf pack, is also good it allows the kiln temp to even out. Good luck with the new approach I’m sure you’ll nut something out. all the best, ang oh and breathe…

  5. Ron says:

    Hey Hannah. I can’t offer much advice on the glaze front as I think you are using different materials. Maybe Doug or Paul will offer up some ideas. I’ll offer some moral support though. Good idea about the tea. I really hope you can get it worked out .

  6. I hate to say anything–me of little experience–but I wonder if you are using the same glaze throughout the kiln. If so, the temperature variation would look like the culprit. As Ang said, do use cone packs throughout the kiln so you really know what is happening. If the glazes are different, then perhaps that is where you have to start looking. Being pressed for time use the glazes that work! Pay more attention to how the kiln is loaded. Gosh, I feel for you. Such beautiful work. How frustrating. Gay

  7. ang says:

    Hi Hannah I had another thought – I’ve always found the digital fire guy to be helpful in understanding whats going on with glaze, you’ll still have to test your local materials though…see if you can come up with a glaze that has a 100deg flexibility. http://ceramic-materials.com/cermat/education/index.htmlyes and prob doug would know UK glaze ingredients quirks..

  8. potterboy says:

    I don’t quite get why it’s hotter at the bottom than at the top. Heat rises, right? So, could there be a crack or hole at the top of the kiln that you haven’t seen, which could let cold air in? Or the elements at the bottom are getting too hot or not switching off or something. Front or top loading? Problem with the door not fitting perhaps?Is there anything you’ve changed recently – make a list. Glaze ingredients? The way you fire? Your last firing seemed to be great – what was different this time?If it were me (and of course it isn’t) I think I’d not be changing a glaze I know works (assuming this statement is true and you aren’t using a new glaze.)I’d be looking at the firing to mitigate problems with the kiln, going slower, even-ing out the temperature, and using cones.Just some thoughts… good luck.

  9. Ron says:

    I agree with Andrew that if you have been using that glaze with good results then I’d not go and try to change it. If it’s a new batch maybe something did get mixed up incorrectly.If all things have remained the same I’d say it’s the kiln. Esp since you just had it serviced. Maybe something is wrong there. So again I’d agree with the others and say: fire slowly, use witness cones, and load evenly as possible.Take care.

  10. paul jessop says:

    I’ve had a number of electric kilns over the years, and in my experience your problems seem to be with the conectors that are dispersing the power to the elements. this would answer Andrews question as to why it was cooler at the bottom, if the bottom elements are kicking out much more heat than the top ones.This can play havoc with your glazes. Of course you do realise you bought all this on yourself, by Praising up Northern Kilns, I think it’s times like this that you will find just how good they are.

  11. paul jessop says:

    One extra thought, some times if a pot is biscuit fired, at a lower temp than usual, that can make a difference to the shrinkage rates and make the glaze not fit. Just a thought. this could have happened when the kiln was playing up the other week.

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