Jump to content
Sign in to follow this  
centered

Raku Firing

Recommended Posts

Hello again, yesterday i fired my zen kiln with some good results, some bad. my question is, in daylight do you see the pots glow? i got my kiln up to 2100 degrees and some pots looked glossy but did not glow a bright orange even when looking through the peep hole and some glaze just looked matt and never looked glossy.(raku burst and lithium slip glaze). when i took the bowl out of the kiln,the raku burst glaze had pooled in the middle of the pot. .I am not sure if i am over firing. last time i fired i got craters, that is why we tried to fire at a higher temperature yesterday. we fire between 1850-2100 degrees by using a pyrometer.

also,

what consistency should the glaze be when it is mixed up? I am not getting a good stonewall white.

thanks for any info you have for me. i am new to raku firing and have loads of questions.

Share this post


Link to post
Share on other sites

I think 2100 is way too high. I had to fire hotter recently because my pyrometers seem off. But even so, I only went to 1900 and the glazes worked just fine.

Sometimes if the sun is shining directly on your glazed pot, it is hard to tell. It definitely won't be glowing or shimmering to determine if the glaze has melted. The consistency of the glaze IMO should be the same as any glaze you would using dipping or pouring. Maybe check your recipe. Is the glaze freshly made?

 

Marcia

Share this post


Link to post
Share on other sites

marcia, thanks for your quick response. i made the glaze about 1 month ago. at that time i went to 1850- 1900 degrees and alot of things came out with craters. i thought it hadn't gotten up to temperature so that is why i went higher this time. i use a pyrometer because i cannot seem to visually read my pots even tho' i look at them through the peep hole at times. now i am considering that my glazes were mixed up too thick or put on the pots too thickly. This is the way I did it in a class I took a while ago and everything came out fine.what is your take on thick glaze? thanks again, you are so great and I love your work. do you ever do workshops in los angeles area?

Share this post


Link to post
Share on other sites

marcia, thanks for your quick response. i made the glaze about 1 month ago. at that time i went to 1850- 1900 degrees and alot of things came out with craters. i thought it hadn't gotten up to temperature so that is why i went higher this time. i use a pyrometer because i cannot seem to visually read my pots even tho' i look at them through the peep hole at times. now i am considering that my glazes were mixed up too thick or put on the pots too thickly. This is the way I did it in a class I took a while ago and everything came out fine.what is your take on thick glaze? thanks again, you are so great and I love your work. do you ever do workshops in los angeles area?

 

Thanks for the compliments. I did a Raku workshop in Jackson Hole in 2009. Nothing in CA.

 

I don't think a thick glaze would crater..could it be boiling... like in over cooked?I've seen a lot of thick rake glazes but thick will melt..

Usually raku glazes bubble but not crater..maybe it is just semantics. I think it looks more like a pancake ready to flip over.

Try the glaze on thin and see if there is any difference. Even try it in an electric kiln to ^06 and see if it melts like you expect.

If it does, then maybe the pyrometer is off. Next rake firing put some cones in the kiln to see what you're getting. How fast did you go?

 

Marcia

Share this post


Link to post
Share on other sites

it took approx. 50 minutes for the first firing then 10-15 for the next 3. i can get my kiln up to temperature in 15 minutes but was told it may be too fast.

 

Yes, maybe a little fast but I had a wood raku kiln that was much faster...3.5 minutes by the end of the day. No pyrometer. It was a great class experience. Could be we were very hot in those firings. Just check what may tell you more, like putting a test piece in a ^06 bisque.

Marcia

Share this post


Link to post
Share on other sites

Hello again, yesterday i fired my zen kiln with some good results, some bad. my question is, in daylight do you see the pots glow? i got my kiln up to 2100 degrees and some pots looked glossy but did not glow a bright orange even when looking through the peep hole and some glaze just looked matt and never looked glossy.(raku burst and lithium slip glaze). when i took the bowl out of the kiln,the raku burst glaze had pooled in the middle of the pot. .I am not sure if i am over firing. last time i fired i got craters, that is why we tried to fire at a higher temperature yesterday. we fire between 1850-2100 degrees by using a pyrometer.

also,

what consistency should the glaze be when it is mixed up? I am not getting a good stonewall white.

thanks for any info you have for me. i am new to raku firing and have loads of questions.

 

 

When you say craters do you mean the glaze was bubbling up while in the kiln or that it was pock marked when you removed it? I fire with an old electric that we have stuck some gas burners and fans under and when it starts to bubble i increase the oxygen and it disappears. I'm not entirely sure what causes that but it has proved very successful and given great results. I am fairly certain that we never go above 1900 and the pots are glowing orange when they are pulled out.

Also i have seen several people talk about trying a thinner application of glazes on raku pots to get similar results. I tested two different consistencies with a copper sand glaze and actually achieve a much more lustrous finish with the thinner glaze.

Share this post


Link to post
Share on other sites
Guest JBaymore

Most American raku glazes mature in the 1800-1900 F range when brought up on the typical fast cycle of raku (keep in mind heat work....not absolute temp). 2100 is pretty darn hot for most of them unless you are headed up like a rocket.

 

Many raku glaze formulations are sensitive to reduction conditions in the chamber when they are going through the melting phase. If, in the intent to get the kiln to temp quickly, you tend to "gun" the burner, it is possible that you are creating reduction in the chamber when you DON'T want it. This will cause a delay in some reactions in the glaze and then result in serious and sudden outgassing as the glaze is really starting to melt. Instant "craters".

 

This unintended reduction situation is a common mistake that people new to gas fired raku kilns often make.

 

As was already mentioned, another possible source for "craters" is the glaze being seriously overfired and it is literally boiling. The fact thjat you are saying your glazes seem to be coming out "thin" would tend to maybe support this idea.

 

A standard method to check glossy raku glazes for their maturity in a firing is to place a solid metal rod into the kiln (an old glassblowing punty is great) and hold it near the surface of a piece. The relatively cold rod will create a reflection in the melting surface of the glaze. In that surface you can then see the normal evolution of bubbles in the maturing glaze. When the glaze has JUST stopped its bubbling, it is "done". Ready to pull.

 

This test of course does not work for all glazes. But it works for a lot of them.

 

best,

 

.............john

 

 

PS: And if some pots truly were not glowing..... it is POSSIBLE that your kiln is firing very, VERY unevenly. If these pieces where then cratered...... that is because they were WAY underfired and the glazes were doing exactly what they should have been doing at those lower temperatures....evolving gases as the chemical reactions were going to completion...with sintering and early melting making the glaze layer sort of like thick toffee.

Share this post


Link to post
Share on other sites

I use matt glazes in raku so I am dependent on a pyrometer to get to the temperature that works for my desired effects.

I like the idea of the iron punty reflecting in the glaze...which is a good indicator if the glaze is a luster or crackle glaze.

Thanks John.

Marcia

Share this post


Link to post
Share on other sites

Hi I have been using Gertsey Borate in my Raku glazes but now I am unable to obtain it does anyone have any suggestions what I could replace it with/

 

 

There are still places that sell Gerstley Borate online. I just bought some last month from Clayworks Supplies in Baltimore. Their website is http://www.clayworkssupplies.com . You can order it online and have it shipped to you.

 

In the community center where I teach my classes, we have replaced Gerstley Borate with Gillespie Borate. Generally speaking there hasn't been any noticeable change to any of the glazes' appearances. Some complain that one of the glazes is not as shiny anymore, but I think that has more to do with firing temps than the borate.

 

Hope this helps.

 

Mea

Share this post


Link to post
Share on other sites
<br>
<br>Hello again, yesterday i fired my zen kiln with some good results, some bad. my question is, in daylight do you see the pots glow? i got my kiln up to 2100 degrees and some pots looked glossy but did not glow a bright orange even when looking through the peep hole and some glaze just looked matt and never looked glossy.(raku burst and lithium slip glaze) <a href="http://letswatchmovies.org" class="bbc_url" title="External link" rel="nofollow external">free online movies</a>. when i took the bowl out of the kiln,the raku burst glaze had pooled in the middle of the pot. .I am not sure if i am over firing. last time i fired i got craters, that is why we tried to fire at a higher temperature yesterday. we fire between 1850-2100 degrees by using a pyrometer. <br>also,<br>what consistency should the glaze be when it is mixed up? I am not getting a good stonewall white. <br>thanks for any info you have for me. i am new to raku firing and have loads of questions.<br>
<br><br>Great post! It's very nice. Thank you so much for your post.<br><br><br><div>

 

 

 

My intention is not to sideline the original poster's question and this topic...... but

 

patrick198....

 

this forum is actually about ceramics and is really not a website that you should nonchalantly use just to slip in your "free online movies" link as you've done in both of your postings since signing up as a member this morning.

 

A generic reply that you added at the end to simulate a ceramic member actually interested in what we have here such as ...."Great post! It's very nice. Thank you so much for your post" .... hardly makes it valid, in my thinking. With no disrespect for your business or desires to link us to watch"free online movies"... I would bet that you didn't even read what this posting was about!

 

Am I wrong on this matter? Or is it O.K. for spammers to do that sort of thing here? Correct me, people, if I'm wrong here!

Share this post


Link to post
Share on other sites
Guest JBaymore

Anmeriswede,

 

I have already hit the "report" funmction (on the bottom left hand side of every posting) for this one. I have also done so on a few other SPAM postings on these boards.

 

This is just that........ SPAM. Might be a bot... or might be a person that gets paid to spam boards that have anti-bot controls in place.

 

So hopefully the mods will delete it and this guys' account.

 

best,

 

.............john

 

 

Share this post


Link to post
Share on other sites
Guest JBaymore

I can't quite figure out what is going on. The rest of the person's post seem legit...

 

 

Matt,

 

I'm a longterm mod on another forum.

 

This is a technique that gets hyperlinks onto legit postings. It does a "quote", inserts some boilerplated benign positive "good post" phrase, and then simply puts in a link to a url for the porn stuff or whatever they are pushing.

 

If the forum signup does not use a "captcha" anti bot signup procedure, an automated script can do this stuff... spamming the boards withj no human intervention. In les spphisticated situations, a human just goes around making these posts (they get paid ...albeit poorly.....to do it).

 

The "issue" is the quote with the url link simply inserted.

 

best,

 

.................john

Share this post


Link to post
Share on other sites

I can't quite figure out what is going on. The rest of the person's post seem legit...

 

 

Matt,

 

I'm a longterm mod on another forum.

 

This is a technique that gets hyperlinks onto legit postings. It does a "quote", inserts some boilerplated benign positive "good post" phrase, and then simply puts in a link to a url for the porn stuff or whatever they are pushing.

 

If the forum signup does not use a "captcha" anti bot signup procedure, an automated script can do this stuff... spamming the boards withj no human intervention. In les spphisticated situations, a human just goes around making these posts (they get paid ...albeit poorly.....to do it).

 

The "issue" is the quote with the url link simply inserted.

 

best,

 

.................john

 

 

thanks John:

 

I never even noticed the "report" button, I appreciate your bringing it to my attention.

 

Regards,

Charles

Share this post


Link to post
Share on other sites
Guest JBaymore

I do not understand what is being said here? Did I post something that was wrong or was it someone else? sorry if it was me. Please explaine.

 

 

Not you!!!!!! No worries.

 

Some spammer called patrick198 quoted your posting and inserted some hyperlinks inside your quote to some other site. Sleezy crap.

 

Looks like a mod deleted the offensive quote posting.

 

best,

 

............john

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.