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SueG56

Member Since 04 May 2013
Offline Last Active May 25 2013 09:32 AM
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Posts I've Made

In Topic: Newbie questions about firing and mildew

05 May 2013 - 10:45 AM

Oh... duh. I did not realize the china paints were the OVERGLAZE!

In Topic: Newbie questions about firing and mildew

05 May 2013 - 09:16 AM

Wow! Thanks!

Reading your post and the link you posted, I find multiple things that I could have done wrong... which brings up more questions (isn't that always the way?)

Since some of the pieces have not been fired at china painting temps and still have the spots, I'm thinking that the cause of my problems happend before I got to that stage. Here is where it is going to be painfully obvious that I have no idea what I'm doing:

What I've been doing up till now is keeping my little kiln on high, loading it and firing it to the temp I want it. (I know... I know) My story is that I didn't care about the translucency business, since I was going to paint over them anyway. Who knew it was more complicated than that? Not me! I'd bisque fire, sand the pieces down, refire to cone 6, and glaze with my 06 glaze. I have not been cracking the top of the kiln during the glazing stage (or at all for that matter). Are you all cringing yet? The pieces have been laid on kiln shelves and placed fairly closely together. I don't have any fancy equipment on my little doll kiln - only a kiln sitter that turns the kiln off when the pyrometric bar bends to let me know I've reached the proper temperature.

And here is what I think you are telling me to do: Please correct me if I am wrong! I have already bisqe fired the butterflies to 04. Am I to understand I can get a clear glaze that fires to cone 6 and apply it to the bisqued pieces now, thereby saving myself a firing instead of using the cone 06 glaze? When I do fire to cone 6, am I to do this slowly or does it not matter since the pieces are already bisqued? Whichever glaze I use, I will need to vent the top of the kiln to allow gasses to escape during the glazing stage. And now the really stupid question - how do I know when I have reached 650 degrees and can close the top of the kiln? How far open should the top of the kiln be during this stage? Would a 1" kiln post prop it open enough or too much? Does anyone know how much of a temperature increase each one of those little dots on the temperature knob represents? And last but not least, if I do decide to keep using the 06 glaze, can I set the emp on high and fire away, or does it need to be done slowly as well? Oh, wait... one more question - can I use cone plaques to prop my pieces on? If so, do they need to be coated in kiln wash first?


Sorry for all the questions - I really appreciate the opportunity to pick your brains -- and your patience with someone who obviously doesn't know much about ceramics and using this kiln!


Sue G

In Topic: Newbie questions about firing and mildew

04 May 2013 - 08:53 PM

Nope. They have not gotten wet after firing, nor have they been sitting around. Tried the clorox and it did nothing. The black spots go all the way through the one piece that had the paint on it and stops just short of the bottom of the piece. If it was the china paints, it went through the cone 06 glaze and then into the porcelain. On the other piece I broke it was from the bottom up - i.e. the back of the piece has the spots on it and the top (where there is glaze) does not.

I am using Highwater Clay porcelain http://www.highwater...21&ParentCat=37



The kiln shelves are clean - nothing with black iron oxide (don't even know what that is - I fire just the porcelain, the glaze and then the china paints)

Sorry for the crummy picture. You can only get so close!










In Topic: Newbie questions about firing and mildew

04 May 2013 - 06:37 PM

Here are a few of the pieces. The one on the bottom left has had one firing with china paints. The other two have had none, but they still have the black spots, so it doesn't seem as though the black spotting is coming from the china paints.

In Topic: Newbie questions about firing and mildew

04 May 2013 - 06:23 PM

Anything that has been fired in a kiln should be sterile. No mildew, no bacteria, no virus, nothing. Even if there were water or organic material left, it would be sterile. If what you are seeing is really mildew, it is not coming from clay which has been fired. I am wondering if it is mildew or something else that looks similar. It is common for unfired, wet clay to get moldy, especially if it sits around in plastic for awhile, but I don't know how mildew would grow on your fired work. Do you have mildew on other things in your studio that might be contaminating your finished pieces? Is this only where they are painted? If so, maybe it is something in your paints.



There are black splotches on the fired pieces. I think I have thrown all of them out as they come up but I will see if I have any more and post a picture. The clay is new - no mildew on that. No mildew anywhere around either. The paints are freshly mixed with oil based medium. The first batch I fired to 015 and then the second batch I fired to 017. I will have to see what happens if I fire some blanks to 015 without adding china paints to them. It is very frustrating to get that far and have the splotches appear!