Wednesday, 22 August 2012

Glaze Firing, The Inquest Begins!

Well, hmmm, this is tricky, i'm putting these up, but feel a tad embarrassed to do so. I like to keep all my faults hidden, especially with all you potters looking on! When i finally dared to open the kiln i was filled with a mix of deflated spirit and some kind of satisfaction. The kiln had finally fired a glaze firing, the pots had survived a journey, nothing stuck to anything etc etc. they were.... "ok"... but they weren't right. For a start i had expected the body colour to be darker... not so orange.. i have orange pots! Matt had fired one of my pots for me a while back and i had some expectation of colour. Why did it do that? this is where my lack of clay knowledge becomes (embarrassingly) obvious. Was it John Cleese who said "every Englishman's wish is to make it to the grave without embarrassing himself"? I'm a true Englishman. The glaze colour may be ok if it was over a darker tone, anyway i think I want a slightly more golden glaze, so will add a bit of iron. The main problem was the glaze pinging off !! Ha ha( i can laugh now... just). Shivering, is it? Anway it was only apparent at first on a couple of rims, but then about 3 hours later as i sat working on a new piece i heard the terrible ping, ping. I threw a cover over the pots to stop any stray shards! It was mainly the handle on that owl cup, which was a shame as that one initially seemed the best. There, one unsuccessful glaze firing. I'm not sure if just lowering my bisc temp (to what Matt and Doug had told me!) will resolve that issue? I'm sure it will help. I felt pressured slightly to increase the bisc temp from local advice. Sorry att, your student let you down and won't be doing that again!!). I bisqued to 06 and glazed at 03. I'll try my 07 bar for the next bisc. What about the colour the body fired to, how does that change? Should i glaze higher?... can i glaze higher with this lead glaze? Now i wish i had a bit more education!! Like i said it's embarrassing, but hopefully a relatively small hurdle. I felt a bit overwhelmed and... stuck, but then we took the boys out to Port Lympne Wild Animal Park( highly recommend it) on Sunday and it helped me get perspective. It was just a very small kiln load of not many pots, no biggy in the actual real World!! Now it's out here in the open, advice welcome but go easy... don't embarrass me! ; )

The kiln load, a mix of small stuff mostly early pieces

Shame about the glaze on that handle. i would have used this little fella.
This bottomless cylinder is now holding pens and pencils in the studio. A permanent reminder of my failings!!
only showing mild signs of losing bits of glaze on the rims
I really liked this fella, but now he has a tiny flake off the top. The top had a big old orange blush on it, which is wrong, but i kinda liked it. Tell me why though.
just a couple of flat pieces of scrap, but these seemed fine, no issues with the glaze. Maybe i just make these... for ever!!


  1. Dude, the hard part's over, you make really cool stuff and you got a kiln. Now it's just figuring out the glaze chemistry and now that you are aware of problems they can be fixed. I however, am not the one to offer advise. See why I use terra sig? Me and glaze are not friendly. I can't even remember how many pots I have thrown out from problems like these! Get your pals that know a thing or two about glazes to check out what you have there and the solutions should be simple to fix. Don't feel bad about putting up the work on your blog, it's a great way to learn. I looked back over my blog posts the other day and I can't believe how many broken and f'd up pots I have posted over the years!! hang in there, it's all lessons :)

  2. I just remembered.... we had this problem with a white majolica glaze pinging off of earthenware at a studio I worked for. The problem turned out to be that the glaze and the clay body did not fit. If you google shivering, there is lots of good information on how to correct that. You can add feldspars and frits to your clay, etc. Quite a bother it seems to me. I think I would rather find a clay and glaze that like each other :) as I said, I'm no expert, I learn everything through google, haha!
    One other thought, I bisque to 04. When I was having pinhole problems, it turned out to be my bisque temps. Good news is that these things are fairly simple to figure out and correct :)

  3. So sad that the owl is not making it. He is definitely a keeper! You could try refiring it with more glaze on the bare spots.
    I bisque and glaze at the same temp, ^04. I will not attempt to make any guesses about your glaze and firing as I am pretty sure materials and clay are markedly different from what is here in the USA. If it's scintering the clay is too big for the glaze at finished temp. One thing Linda Arbuckle warns about is making sure the body is absolutely clean with no grease or other stuff on it, or bad things happen.
    Don't apologize for showing failures. One of the things I really like about blogging is the willingness to share information and possible solutions to fails.

  4. P.S Are you a member of Ceramic Arts Daily? They have informative daily postinga and forums that address myriad problems......all free! ceramicartsdaily-dot-org

  5. Hey Scott, I think these pots look really great. The color is not bad, just not what you were expecting and your sgraffito looks super with the glaze covering and color.

    I don't know about the glaze coming off. My friend Andy over there had the exact same problem. Just to be clear I wanted to ask, is it just the glaze that's coming off or is the slip coming away too? If the slip is on there then it's a glaze problem, if it looks like the slip is popping away and taking the glaze with it then it maybe a slip issue.

    So, as Suzi said, materials are different here and you are using some sort of lead bisilicate or such. Are these Matt G's recipes? Slip and glaze? If so I'd talk to him and try to do exactly what he does. He is getting good results.

    Really good job on the first go!! Pots look great. Get that glaze sorted and you'll be rocking!

  6. Hey, did that little cup without the slip on it have any glaze problems?? Was most of this flaking on rims or edges?

  7. Hey folks, thanks for all your extended comments. I know this is all a lot different from the States as it's dealing with Lead Bi glaze. I've made my peace with it now!
    Tracey, Yep it's definitely a 'fit' thing and i do think it's a minor issue. Having a working kiln is the good thing! Getting it free and having sat around for 10 years plus, i was worried it might not work at all.
    Smartcat, thanks. it was certainly a shame about that owl.. he also had a little lid to keep my cuppa hot, but that taught me another lesson... leave some wiggle room for glaze thickness! ha. one redundant lid.
    Ron, That un-slipped cup gas no visible problems, but the slip stayed on the others, so it's clearly just a glaze issue... but i guess it's more the fit of the glaze to the slip than the body. It is Matt's glaze mix and he has reported in now... My bisc was too high and so was the glaze a tad. That's where the issue is i think. The glaze just shrunk a bit too much, too much heat.
    I'm going to give it a bash with those lower temp cones and see if it resolves it. Ron, the glaze colour is ok, but for me i think a bit more amber. When i get going properly I'll probably have a bucket of both.
    Better get making a batch of things to test the new temps on. there'll be a rush of pinched pots and slab cylinders being made soon. My bigger pots will just have to wait until i fix this issue.
    Thanks all!

  8. Glad you to talked to Matt. Hopefully the temp change will help. Good idea to make some simple pots and fire again and see how things go. The color issue can be worked out with some tests of increasing or decreasing iron to find the color you like.

    Really excited for you.

  9. When I'm trying out glazes and firings. I just throw a bunch of 1 pound cylinders. Not only do you have easy pieces to test, you get more practice at throwing. If they turn out ok, you can sell them cheap, if they suck it's not so hard to bash them :)
    Good luck!

  10. Tracey, i like that. I was thinking the same the other day. I want to use this time, while i figure out the kiln/glaze to start getting the throwing side going. I have offer of further instruction, so i shall be doing that, but I'll also just start and test the firing on them. Also gives me things to be a bit more experimental/fresh with the slip and deco. let's see how it goes!

  11. Scott, you're a bloody genius mate! These all look so great! I love them all! Respect due.

  12. Ha ha, thanks Paul! You may be the only one with that opinion. However, there are only a few peoples opinions I actually value, so thanks! If i can only find a bloody cone for the temperature I need. When I do, I'll send you guys a little something for your new abode. Good luck with that move, always stressful events. You'll be glad you did though.