Glazing over-fired bisque
Reglazed stoneware mug cone 6
You might remember that I over-fired a bisque load in my ancient kiln a few weeks ago – the kiln contained work by my after school clay class, but I also slipped in a few of my pieces in the interest of using space wisely. Doh! Anyway, I received a few suggestions about how to salvage the work including glazing it with low fire glazes, doing a cold finish and more. I did the former, but didn’t like it so much, so I decided to try glazing the work to cone 6 again. To do this I placed the empty mug in the microwave on high for 2 minutes until it was almost too hot to handle with my bare hands (but not quite). Immediately, I dipped the mug in a bucket of glaze with a pair of tongs, wiped the bottom off with a sponge and put the mug in the kiln so that I wouldn’t have to handle it again.
Same glaze on a properly bisqued cup
I was pleasantly surprised to open the kiln the next day to find a glazed mug – but there is a catch. The glaze is much paler than its counterpart below that was in the same cone 6 glaze kiln as the mug above. The difference is that the cup in the bottom photograph was bisqued to the proper temperature. It was a good exercise – it shows me that bisqueing to a lower temperature allows more glaze to cling and be absorbed to the bisque ware. I’ve read and been taught that factoid before, but being a visual person and experiencing it first hand really makes it stick. 
Notes: I used the mug one morning and ran it through the dishwasher and used it in the microwave with no ill effects. I won’t be selling the mug either, but am glad that it doesn’t have to end up in my shard pile.
Happy Thursday,
~Cynthia
It Takes a Village…
Village of clay huts by the students in my after school clay class
to forgive my kiln over-firing debacle from last Monday – the kids took it well. It may have helped that I promised to make them each a special “I’m sorry” cup to make amends. It was a good learning moment for them – firing a kiln is still a mystery for them – how hot is 1800ºF anyway? They don’t quite understand the whole concept of turning wet clay into permanent fired pottery since all they see is that I take their creations home with me and bring them back fired like magic! The repairs to fix some of the over firing issues with Jean’s jewelry box didn’t work. Jean took it well and I’m ready to try again. But, that will be a job for another day….
Meanwhile, I spent all day reading lazily on the sofa – the newspaper, back issues of magazines, books and yes, even a bit of internet reading. We have three lap tops in our home and all of them are starting to show their age. I’ve been reading up on other operating systems and have decided to install Ubuntu, a FREE Linux open source operating system on one of the oldest computers, and will delete Windows XP completely. If it doesn’t work, then no big deal – but if it does, it will extend the life of our computers and hopefully make them faster.
Open source software and hardware is a really cool turn of advents. Now, it’s nothing new – Linux is released under GNU or General Public License since 1994. GNU is an interesting business model – people are able to modify and even benefit financially from someone else’s intellectual work as long as attribution is defined. Wired Magazine (one of my new faves) touches on open source in quite a few issues. Companies that are closed and proprietary, like Microsoft, have quite a market share and frankly are afraid of open source because it is a threat to their long term viability. Reading about companies, such as Arduino, an Italian group that manufactures open source electronics platforms for a variety of uses. Pretty cool, don’t you think?
Anyway, it’s a little more work on my part to do the research and homework to install a Linux based system – after all Windows has @ 88% of market share. On the other hand, there are a number of free software applications that can replace everything that I currently have installed on my computer such as Open Office (replaces Microsoft Office Suite), Gimp (Photoshop), Archimedes (AutoCad) – along with a slew of any other kind of free software programming anyone could ever need. I was reading about how many open source contributers consider their efforts to be good old fashioned community barn raising. I like to think of my humble little pottery blog in the same light – I share what I learn, good bad and down right ugly because I enjoy learning from others in the field and I love receiving emails from folks who try making some of the techniques I have posted, including improvements or alternatives.
So, thanks for humoring me and for continuing to read & comment on my blog! 
~Cynthia
I HATE Pottery…Sometimes
Okay, hate is a really harsh word, but that’s what I was screaming yesterday afternoon when I opened my kiln! I messed up – royally. I freaking over fired my kiln *again*. I say that in a whisper, because after I over fired one of my kilns about 2 years ago, I swore I’d never do it again. Same dang mistake too – something touching kiln sitter so it didn’t drop when it reached temp – cone 05. Instead, it turned off when the cone in the sitter was completely burned to a crisp. Who knows how hot the temperature reached inside my ancient Paragon kiln. I use this one to bisque fire work and while I think it’s rated to ^9 roughly 2300° F. So – did it fire to ^ 9? Quite possibly. What was in the kiln – mostly my student’s work from my after school clay class, but I also squeezed some of my work in there including Jean’s custom jewelry box. 
On first glance it doesn't look too bad…
After my discovery, I was banging around, cussing – I think every expletive known to humans escaped from my lips. Luckily, no tender ears were around to hear, save for those of my dogs. Then I got really mad – mad at myself, at the pottery gods, at clay and I actually said I HATE Clay out loud! 9&%$J K &*jy6% %HMK< – you get the picture. I don’t know of any other medium (save maybe glass or jewelry) that what you see isn’t what you always get. That stinks.
So then, after unloading work and salvaging what I could, I started to work on my shelves. Clay & glaze melt from the low fire earthenware my students made littered the bottom shelves. I had my hammer and chisel out banging away at my shelves all the while glancing at the custom box, ready to take the hammer to it as well. But, something stopped me and I went over to look at it again. I mean really look at it – turn it over, inspecting for major issues, besides being a fully vitrified clay object with bubbles.
Can you see the bubbled slip?
The biggest issue is that the slip bubbled on the side that was next to the elements and not really any place else. I’m sorry I didn’t take a photo of the before – but by the time I started taking photos of the piece, I had already taken a grinder to the box and popped most of the bubbles out of curiosity.
I sort of like how the sanded bubbles give the piece another dimension
Then I started asking the clay gods what I was supposed to learn out of this situation…. I’m not sure s/he answered me or not, but I really got to work sanding even more – exposing all the bubbles. I have decided to play around with this piece some more. I’m not sure exactly what’s going to happen or how it will turn out, but I wouldn’t do this intentionally, so who knows? I’ve already sent an email to Jean with my profuse apologies – she’s so nice and still wants a covered box from me – albeit not for her sister’s birthday. My experiment might turn out to be total crap – but I don’t have anything else to lose except time, do I? So, this is back in the kiln this morning with some paper clay repairs – along with a few other pieces from the archives that had “issues” during firing.
These 3 little boxes were also in the doomed kiln.
I’m pretty sure that I can’t glaze these boxes anymore – and they are pretty nice in their nakedness. I could probably play around with some cold surface decoration techniques for these boxes since they’re not intended for food. Both the ^6 porcelain and white stoneware I use fared okay at a higher temperature, unlike the low fire red earthenware clay.
low fire red earthenware house
Ever want to know what low fire red earthenware clay looks like at ^7-9+ ? It’s a nice toasty chocolate brown color and it’s sort of self glazing with a nice sheen on the surface. But, the lid is now attached to the base – and the clay deformed/melted ever so slightly during firing. These will be perfect for the garden or an aquarium setting.
Big sigh…. Note to self – pay better attention when loading the kiln.
~Cynthia
