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Posted by Bubbles_ on September 27, 2007, 6:10 am
Please log in for more thread options Hi! Hope you are feeling better today!
No, I don't post on clayart. Is that a newsgroup, or a forum? I don't like
forums, I keep forgetting to keep up and it ends up that I just drop it.
Hmmm - venting my kiln? Well - I told you about the holes. The kiln is in
the laundry room, so I make sure there are no clean clothes in the room and
then open the window. The room does get warmer, but not too bad.
All the glazes I use are so-called "poison class free" - ie. they are
supposed to contain no poisonous materials. Still, the room really stinks,
especially when I am glaze firing, of course, so I always close the door to
the hallway and have the window open in there.
There is a hitch with me trying to discuss this with the makers of the
glaze, because my German really isn't up to par to discuss this! I tried
talking about it with the boss where I buy the stuff, but even face-to-face,
I didn't understand everything he said, and it just got so complicated that
I gave up. I did catch a couple of ideas, but I thought the gang on here
could get into this in general, as it is happening on other glazes than the
101+100 combination, though that one is the worst.
Have a lovely day!
Marianne
> I'm assuming you are also posting on clayart where you might have more
> luck of overlapping with someone using these glazes.
>
> With that high of humidity don't dunk the pots (I only rinse mine under
> the tap very, very quickly). Dunking them is going to empty the air out
> of them and you don't want that. I would though, wipe them off with a
> damp sponge.
>
> How are you venting your kiln? Clay and glaze materials put off some not
> good stuff...
>
> Since you are buying a commercial glaze material you should be able to
> call them up and get some support. Since you don't know the ingredients
> and they do it is their responsiblity to give you help on this. Generally
> people who sell glazes are all to happy to do all they can to keep their
> customers happy and buying their product.
>
> IMO - There really isn't anything anyone else can do to help unless they
> are familiar with the glaze or know what it is made up with. As I said a
> 40 minute soak is to me overkill.
>
> Thanks for the chicken soup - it always works.
>
> Donna
>
>> Hey again
>>
>> Sorry you aren't feeling well! Get well soon!
>>
>> I think it is "bear" - as in to bear a burden, not the animal - hehe!
>>
>> Okay - I haven't even seen anyone using cones over here in Europe - my
>> teacher doesn't even with her new kiln, and neither did an old teacher of
>> mine. I can't remember seeing any in the extensive catalogue from my
>> dealer, either.
>>
>> I was told that sponging off bisque-ware was only to remove the dust. My
>> workshop typically has a humidity of around 50 %. I guess maybe that
>> should be enough.
>>
>> But, when you mention during glazing, I do sometimes se that just little
>> spots aren't covered - like a little speck of grog. I just dab it with my
>> brush with glaze on it, but could that be part of the problem? I like
>> your suggestion of a little quick dip in water, and will try that later
>> on. I need to get myself one of those potter's pencils that doesn't burn
>> away - and start numbering my pots and writing down their whole way
>> through the processes.
>>
>> The clay I use is this:
>> http://www.michel.ch/michel/katalog/ton_tony.asp?Redirect=True
>>
>> Apollo Steinzeugton 1000 - 1300°C
>> weiss - hellcrème - hellgrau
>>
>> Westerwälder Steinzeugton ( WM2502 ), sehr fein schamottiert
>>
>> Hervorragender Drehton, sehr plastisch, gute Standfestigkeit, auch für
>> sehr grosse Stücke. Einfach und gut im Trocknen. Guter Glasurträger. Raku
>> möglich.
>>
>> Technische Daten
>> Rohbrand 950 - 980°C
>> Brennbereich 1000 - 1300°C
>> Sintertemperatur 1220°C
>> Brennfarbe weiss - hellcrème - hellgrau
>> Schamottierung 25 % 0 - 0.2 mm
>> Trockenschwindung 5 %
>> 1000°C 1100°C 1200°C 1260°C
>> Brennschwindung 0.5 % 3 % 5 %
>> Wasseraufnahme 14 % 9 % 3 %
>> WAK ( 20 - 500 °C ) 7.2
>>
>> I'm stuck on translating any of this at the moment, but will try if you
>> don't get the general gist of it.
>>
>> These are the glazes I use.
>> http://www.michel.ch/michel/katalog/glasur_1250.asp?Redirect=True
>>
>> The one I have most problems with at the moment is 101 with a glaze
>> improver over. The improver - number 100 - makes it go different blues
>> and greens and blacks when I add it on top. Fantastic colors, but the
>> bubbles keep showing up. Mind you, I had a bubble on a matte glaze - 404,
>> I think - on this last high firing. I don't have this problem at all with
>> low-fire stuff - at 1050 C, same as my bisques (that way I can mix them a
>> bit and get a full kiln faster).
>>
>> My kiln is teeny - only about 2 feet wide and maybe 3 feet tall inside -
>> so I wouldn't expect huge temperature ranges inside except when firing
>> with the holes open - on in the lid, one right down at the bottom.
>> possibly even below the bottom shelf. I open those about up to 650 then
>> close them. I can't remember any bubbly piece specifically being by the
>> open holes, and glazes only really start to melt well above 650C, don't
>> they?
>>
>> I'm going to go fire my kiln now. It is a bisque, and I will check my
>> glazes to see if they can be fired higher than 1050 - there are a couple
>> I have that shouldn't be, which is why I have stayed at that temp, and I
>> have some glazed stuff going in now.
>>
>> Thanks again for your time and input!
>>
>> ***virtual chicken soup for you to get better on***
>>
>> Marianne
>>
>>
>>> Hi Marianne!
>>>
>>> I'm home sick with flu and not functioning 100% so bare (or is that
>>> bear) with me...
>>>
>>> First, you should use cones on all firings or at least do regular spot
>>> checks. You need to know what heat work you are getting not just what
>>> temperature you are going to and you need to know that for different
>>> spots of your kiln.
>>>
>>> You can try bisque firing to cone 04 (1060 C). I only fire to 06 (995
>>> C) and have no problems but I mix my own glazes and know the materials I
>>> am working with. Firing to 04 is often recommended. Do you make up
>>> your own glazes or are you buying glazes? If you don't fire with cones,
>>> see if you can beg, borrow or steal some until you can buy your own, at
>>> least to check your next bisque firing.
>>>
>>> You can get bubbles before if your pot is very, very dry when glazing. I
>>> am one of the few potters out on the eastcoast that I know of who rinses
>>> off their bisqueware before glazing. It is a really, really quick rinse
>>> so the pots are still absorbant. I was taught in the desert environment
>>> where it was so dry you could soak your bisqueware in water and five
>>> minutes later they would be bone dry. In fact you had to dip them in
>>> water or the glaze bubbled up. You can wipe down your pots with a damp
>>> sponge to both clean them off and decrease bubbling on the dry glaze
>>> surface. This is probably not the problem with your glaze however. It
>>> is something you would notice by now.
>>>
>>> Let us know about the glazes you use. (if you mix your own, what
>>> ingredients - better yet what recipe are you using).
>>>
>>>> Hi DKat! Good to see you!
>>>>
>>>> I am firing bisque to 1050 C.
>>>>
>>>> It usually happens with the really glossy glazes, but I actually had
>>>> one bubble on a matte glaze this time as well.
>>>>
>>>> Since the bubbles go all the way in to the clay, do you think I might
>>>> be bisque firing too low, so that there are "substances" left in the
>>>> clay before the glaze firing?
>>>>
>>>> I do think my oven's thermometer might show a bit higher than it
>>>> actually is, so maybe just increasing to 1060 or 1070 would help?
>>>>
>>>> Once again - any input greatly appreciated! Especially since I have a
>>>> full load for bisque firing ready.
>>>>
>>>> Marianne
>>>>
>>>>
>>>>
>>>>> How high are you bisque firing to? What glaze is this happening with
>>>>> (is it all glazes, just one, a mix)? We need to know more before
>>>>> suggestions would be of much use. 40 minutes of hold time is way more
>>>>> than you should need so something is not as it should be.
>>>>>
>>>>>
>>>>>> EWWWW!!
>>>>>>
>>>>>> I keep getting bubbles on my finished pieces. I have tried up to 40
>>>>>> minutes hold time at 1270 degreess, but they still show up! I am
>>>>>> getting rather frustrated by it all. I can "repair" them by adding
>>>>>> glaze to the holes (that are more like inverted craters going all the
>>>>>> way down to the clay) and refiring once or even twice, but I have a
>>>>>> very small kiln at home, and find it both a waste of space and power,
>>>>>> while at the same time not wanting to "lose" the pieces.
>>>>>>
>>>>>> Any ideas on other things I could try? Last kiln was 6 hours to 650,
>>>>>> then up to 1270 and hold for 30 minutes. The cooling was over almost
>>>>>> a day. Policy being that over about 400, I don't even let the cool
>>>>>> air of the laundry room in, but after that, I take out a couple of
>>>>>> plugs (top center and bottom) and under 200 I start opening the lid
>>>>>> of the kiln a little. That shouldn't affect the bubbles, though, as I
>>>>>> am sure they have set at much higher temperatures.
>>>>>>
>>>>>> BUT - AGH!!!
>>>>>>
>>>>>> Any input and suggestions greatly appreciated!!!
>>>>>>
>>>>>> Marianne
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>
>
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