Jump to content
potterkimme

Firing An Accidentally Glazed Green Ware Pot?

Recommended Posts

potterkimme    0

Goodmorning everyone! I am new to the forum and have a question. A low-fire sax clay was accidentally glazed with a low-fire glaze and clear glaze on top. Oops! Should I/could I fire this piece with a few other low-fired glazed pots? Any suggestions?

 

I am happy to meet you all and look forward to reading/discussing pottery with you here :)

 

*sax low-fire 04

*Amaco low-fire glaze 05

Share this post


Link to post
Share on other sites
Tyler Miller    331

How dry was the pot when you dipped it? Generally, if glazing greenware, the pot has a little moisture left in it to help deal with the shock of the extra water being added.

 

It could be fine. Maybe.

Share this post


Link to post
Share on other sites
oldlady    1,323

i fire glazed greenware all the time.  it has to be done slowly to be sure all the moisture is driven out of both clay and glaze.  not knowing anything more, i cannot say how you can insure the dryness of the pot except to say go  s l o w l y.

Share this post


Link to post
Share on other sites
potterkimme    0

Thank you both so much. The pot had been dry for weeks. That's why the accident happened. It appeared very similar to the already fired ones. I only realized it was greenware when I wiped the bottom and it showed on my sponge.

Edited by potterkimme

Share this post


Link to post
Share on other sites
RonSa    189

I just did that on purpose and it fired ok. I was just afraid to put on to much wet glaze on it and I wound up not putting on enough. Next time I won't be so afraid.

Share this post


Link to post
Share on other sites
potterkimme    0

Thank you RonSa. I am going to let it really dry and then try firing it. I think I'm going to go with a slow fire as suggested. I guess we'll see what happens.

Share this post


Link to post
Share on other sites
Joseph F    867

I single fire all my work. Which means it wasn't bisqued. As all the others here have said, I think it will be fine, just make sure that you go slow between 200F and 500F, after that you can fire like normal. 

 

Worst case is that it explodes, medium case is that it has some glaze defects, best case is nothing looks any different than if it was bisqued. Only way to know is to experiment. You could end up realizing that you don't need to bisque at all. 

Edited by Joseph F

Share this post


Link to post
Share on other sites
Denice    243

If this accident works out and you want to try glazing greenware with other glazes, test them first.  Off gassing can affect some glazes.    Denice

Share this post


Link to post
Share on other sites
Tyler Miller    331

I just did that on purpose and it fired ok. I was just afraid to put on to much wet glaze on it and I wound up not putting on enough. Next time I won't be so afraid.

It ends up going on thinner with greenware if dipping. The water absorption is less than bisque. Especially since its best to dip greenware when just a little water is left.

Share this post


Link to post
Share on other sites
RonSa    189

Thanks Tyler that makes sense.

 

I had sprayed the glaze on with an airbrush since it was a very small teaspoon holder.

Share this post


Link to post
Share on other sites
potterkimme    0

Thank you all for helping. I am going to let it continue to dry. I may try and forget about it for a week or so. I have a smaller kiln and only put in lesser pieces or none at all with it incase of accident 🤔

Edited by potterkimme

Share this post


Link to post
Share on other sites
potterkimme    0

I single fire all my work. Which means it wasn't bisqued. As all the others here have said, I think it will be fine, just make sure that you go slow between 200F and 500F, after that you can fire like normal.

 

Worst case is that it explodes, medium case is that it has some glaze defects, best case is nothing looks any different than if it was bisqued. Only way to know is to experiment. You could end up realizing that you don't need to bisque at all.

Share this post


Link to post
Share on other sites
Joseph F    867

Depends on how confident you are that your work is dried. If your unsure do 100F an hour. If your confident do 250F an hour.

Share this post


Link to post
Share on other sites
RonSa    189

Here's something I do in woodturning to determine how dry a roughed out wooden bowl is. 

 

I place the bowl on a scale and record the weight. I do this every couple of days and when the bowl stops losing weight its as dry as its going to get.

Share this post


Link to post
Share on other sites

Glaze on green ware? There is a thousands-years-long tradition, particularly in Korea and China.  "Raw glazing"  they call it, and they do it all the time.  From sad personal experience, I have two suggestions:

1.  clay based glazes, rather than feldspar based, work much better, particularly if the body clay and the glaze clay are the same material.  Clay is stickier, and will shrink/expand with the body.  Feldspar glazes tend to fall off, flux into the body, or crawl.

2.     Timing is important - apply glaze when leather hard, not wet (it melts to body) or bone dry (it cracks).

Share this post


Link to post
Share on other sites
Judith B    52
11 hours ago, alexanderwilds said:

2.     Timing is important - apply glaze when leather hard, not wet (it melts to body) or bone dry (it cracks).

@alexanderwilds I used to work with a potter who only did single firings. We would spray the glaze en dry pieces and never had any issues. Isn't applying the glaze on a leather hard piece tricker? I feel like the piece would just fall apart from too much humidity once glazed... 

Share this post


Link to post
Share on other sites
bciskepottery    925
10 minutes ago, Judith B said:

 I used to work with a potter who only did single firings. We would spray the glaze en dry pieces and never had any issues. Isn't applying the glaze on a leather hard piece tricker? I feel like the piece would just fall apart from too much humidity once glazed... 

Different glaze application techniques will make a difference.  When you spray, more glaze and less water goes on the ware -- so dry pieces mostly get glaze and not water.  If you dip, you will have to deal with more water and will need to dip at a stage where adding that much water would not affect the ware. 

Share this post


Link to post
Share on other sites
Joseph F    867
2 minutes ago, Judith B said:

@alexanderwilds I used to work with a potter who only did single firings. We would spray the glaze en dry pieces and never had any issues. Isn't applying the glaze on a leather hard piece tricker? I feel like the piece would just fall apart from too much humidity once glazed... 

I have a liner glaze that I apply when the mug is still cold to the touch. Basically the stage you add handles, or leather hard. I do it right after I trim.

My other glazes I apply at bone dry by spraying. I could apply them sooner probably but it just makes no sense to handle them at different stages. 

Of course I think it all depends on your application. I spray, so it really doesn't matter for me. I spray from a distance. So my glazes go on pretty much dry.

Share this post


Link to post
Share on other sites
Joseph F    867

@glazenerd

They talk about veegum in that thread a lot, what does it do to the properties of a glaze slurry? I have never used it before? And how does it relate to single firing?

Share this post


Link to post
Share on other sites
glazenerd    816

V-gum is a binder for glazes: that like any gum keeps them in suspension. In this case however, because V-gum also has a tacky quality, they are using it to help bind glaze to the piece, and as a brushing medium.  I started to once fire some time back in order to save time, save element life, and to save money. I developed my own nerd suspender that does what V-gum does for 1/2 the price. 

My schedule is:

160f to 1150F ( gets you past quartz inversion at 1063F) 

250F to 2050 F

125F to 2230F ( no hold in smaller kilns)

i do not have pin-hole issues, good uniform melt, and vitrified. Not a fan of 2190F with long hold, although it is common practice in pottery.

Share this post


Link to post
Share on other sites
Joseph F    867

I dont have pinholing issues either. But I hold at 550F for 30 minutes and again at 1600F for 60 minutes. I also don't like the 2190F hold for an hour either. I go to cone 6 and hold for 20 minutes. 

 

Share this post


Link to post
Share on other sites
Dick White    155

Joseph, a question about your holds. It seems logical to me to have the 30 minutes at 550F as that's a bit above ignition for many organics and this would encourage/improve burnout - or maybe you have a different reason. But I'm coming up blank in my little head what might be happening for an hour at 1600F?

Share this post


Link to post
Share on other sites
Joseph F    867

@Dick White

11 hours ago, Dick White said:

Joseph, a question about your holds. It seems logical to me to have the 30 minutes at 550F as that's a bit above ignition for many organics and this would encourage/improve burnout - or maybe you have a different reason. But I'm coming up blank in my little head what might be happening for an hour at 1600F?

I am off gassing some of the materials in my glazes(talc), I read somewhere that LOI of some of my materials happens around this period, so I was hoping to get it over with here instead of later on as glazes are bubbling and such. Also hoping to burn out any final carbons/junk in my clay. If I skip this hold my liner glazes develop a few pinholes. So it is definitely doing something. I don't have any really solid foundation behind this hold besides numerous test firings to rid myself of pinholes when single firing a darker iron clay body.

I started by just doing from 300F to 2000F at 450F an hour. I had a lot of pinholes. So I added the hold at 500F. Which removed some of them. Then I was reading that a lot of carbons start burning out around 1300-1600F. So I decided to add a hold at 1500F for 30 minutes. It didn't do much, so I increased it to 1550F; seemed slightly better. So I went to 1600F for an hour and it seemed to work the best. 

I personally thought that 1600F would be too high, since almost everything I have read says that most carbon burnout happens around 1350-1500F. 

Does any of this make any sense? I am not real good with all the chemistry stuff. I just go by trail and error. I change one thing at a time in my firings or glazes and write everything down. This way I know the cause/effect of my change. 

EDIT: I should also say that my liner glaze is very heavy in the gerstely borate. Which I don't like using, but it is such a fantastic glaze. I really need to get off my but and remove that material from the recipe by substituting, but I just haven't gotten around to it. Maybe that is the reason the 1600F hold does a lot, since GB is probably starting melt by then? I don't know. I wish my kiln was clear so I could look in it while it fired!

By all means if you know of a better solution I am up for it. I would like to lower my total schedule time. I am currently around 19 hours(3 of it preheat for wadding).

Thinking about it now. Maybe I should try something like: Get to 1400F then change my ramp to like 50F an hour till 1650F. Might be better. I will test that next time.

Edited by Joseph F

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×