Tuesday, March 10, 2009

Chun glaze


Have had a rather busy few days, but managed to get some more glaze testing done. I was pleased with this little bowl, it went in with the glaze test firing. There are three glazes used in all, and most of the colour comes from light being scattered within the glaze. I was pleased to see colours that ranged from violet through blue to pale green.

Very tired at the moment, so I am keeping this brief. I am sorting through photos of kilns that I have built, and will post them on this site quite soon. It is quite fun looking back at the progression from the first wood fired kiln, that had a chamber of only about 1 cubic foot, through to the one I use now; and the photos might prove helpful to someone else one day, who knows!

27 comments:

Judy Shreve said...

What a gorgeous blue! Is that a temmoku on the rim?

Peter said...

Hi Judy,

There are three glazes on the pot that are put on one after the other in layers. The first one to go on is a temmoku glaze, then there is a clear glaze that I modified by adding about 3 percent rutile and one percent of copper in it, and on top of that is a chun (jun) glaze. I can post the recipe some time, but am just about to race out the door now to catch a bus.

Nice to here from you. Best Wishes.

Anonymous said...

Do you have a Chun glaze recipe for cone 6 oxidation that you can pass on to me?
Thank you

Teresa

Peter said...

Hi Teresa,
I would love to be able to help with a recipe for you, but I haven't done a lot of cone six firings, so I'm probably not the best one to ask. I use an Emmanuel Cooper chun recipe quite a lot, which I usually fire between cone 9 and cone 10. This recipe is really supposed to be for Cones 7 - 9 and I was wondering if you could adapt it to cone 6 by adding some borax frit, probably 10 - 20 percent??
The recipe is as follows
Potash Feldspar 46
Dolomite 6
Zinc Oxide 6
Whiting 10
China Clay 2
Silica 30

I find this gives a good blue chun when used over an iron bearing slip or a tenmoko type glaze. Reduction is not needed for this glaze, and I have good results in an electric kiln. It does seem important in oxidation to use an iron bearing slip or glaze under the chun for the best results. Probably less important in reduction where iron is being drawn through the glaze from the body of the pot.

June Perry of Shambhala pottery has some interesting looking cone 6 glazes on her main web site http://www.shambhalapottery.com/technicallinks.html
It might be worth leaving a question on her blog http://shambhalapottery.blogspot.com/

Good luck with it, P.

Anonymous said...

I love the blue! Im firing in a Bailey gas kiln (cone 10) with white stoneware and would love to have the recipes (i know you said you used 3)
-Bethany

Peter said...

Hello Bethany,
Sorry not to get back to you sooner, I should check my mailbox more often! I see that you made about 3 attempts to get in touch with me.

Thanks for your interest in the glaze, I am really happy to pass on recipes and other technical stuff.

Chūn glaze (Emanuel Cooper recipe) Really for cone 8-9, but I fire 10 – 11 with this glaze.

Potash Feldspar 46
Dolomite 6
Zinc Oxide 6
Whiting 10
China Clay 2
Silica 30
Bentonite 1

This works well for me over a variety of tenmoko glazes or iron bearing slips.


One cone 10 glaze that works well under the Chūn glaze shown above is as follows, (I think this is the one I used on the bowl in the photo you saw),

Silica 41
Potash Feldspar 34
Whiting 16
China Clay 9
Black Iron Oxide 10

I usually pour my glazes, or dip a pot in the glaze bucket, and a certain amount of unevenness is a good thing for these glazes, as it gives a more interesting range of colour. I apply the under-glaze, then usually apply the Chūn glaze over the top as soon as the first glaze is only just touch dry. It does depend on how thick your pots are as to how well they will take more than one application of glaze. Really thin pots get too saturated with water from the first glaze, and you have to wait for them to dry before the next glaze will go on. Probably you could have a lot of success with spraying the Chūn glaze over the under-glaze.

It is worth experimenting with all sorts of under-glazes. I find it does make a real difference as to how the Chūn glaze performs. I have even used them with success over copper red.

I wrote a fairly detailed response to someone recently who asked about my Chūn glazes. I replied to her question on

http://opopots.blogspot.com/2009/01/about-tiles-and-glazes-by-peter-gregory.html

and I have left a couple more recipes there too. Another, more difficult (but rewarding) Chūn glaze, and another under-glaze that is quite reliable.

Good luck with it. Do let me know how you get on.

Ramen Fiend said...

I'm trying to make a hybrid glaze of wood ash glaze and Chun. I use a small woodfired kiln normally used for salt-glazing. I think it gets up to cone 5 at it's maximum. I'm just guessing here though because I can't find cones where I live. I just know what "hot-enough" looks like when I peek in. I want to get a blue-green to dark-green variance and am doing it with punk ash. I know how to get the green, the blue is eluding me.

Any tips or tricks that might help me on my quest would be appreciated.

Peter said...

Hi Ramen,
Welcome to my site. Sadly I am not able to help you with this as I have no experience of cone 5 glazes (or salt firing). Wood ash certainly can be helpful in making chun type glazes, as can small amounts of rutile, or bone ash, or zinc.

Hopefully another potter reading this might be able to add some helpful advice regarding chun type glazes for cone 5.

If you do manage to find something that works for you, do post a comment here and let us know, it might help someone else who is working in a similar temperature range.

Best of luck, P.

mike said...

i converted this to cone 6 (both the glaze and underglaze) using +.25 lithium Carbonate and +10 cluster feldspar. turned out incredible in oxidation and my 30 pieces sold out at my colleges pottery sale. ive also been adding colorants to this and it turns into a great base high gloss glaze.

Peter said...

Hi Mike,

Thank you for letting us know, I am very pleased to hear that the glazes worked so well for you and that you were able to convert them to cone 6. Did you take any photos? I would be very happy to post some on this site and the modified recipes that you used as I know that there are others who would love to do chun at cone 6, and it could be very helpful. Anyway, well done for experimenting and modifying the glaze to fit your requirements. Good to hear from you.
Best Wishes, P.

ang said...

hey peter and mike.....really cool that the cone 6 recipe worked out well...mike what else did you change when you added the lithium and custer feldspar?? I think playing with additions of ash sounds intriguing too peter....most of my chun recipes have bone ash in them of which i have heaps so it's a good thing :P

Anonymous said...

Hi,

Just found your blog and I am overwhelmed with your generous sharing of recipes and information. I am a bit of a part time potter because I am a full time art teacher. I feel like my lack of interesting results with glazing (electric kiln) is partly what prevents me from going further with it.
Just wondering:
1. What type of clay do you throw with to get that beautiful chun/tenmoku combo?
2. How thin are your glazes to get them to layer without cracking and falling off while drying?
3. Do you fully dip in tenmoku then fully dip in chun?
Thanks for the help and the inspiration.
Kind regards, Sarah

Peter said...

Hi,

Just found your blog and I am overwhelmed with your generous sharing of recipes and information. I am a bit of a part time potter because I am a full time art teacher. I feel like my lack of interesting results with glazing (electric kiln) is partly what prevents me from going further with it.
Just wondering:
1. What type of clay do you throw with to get that beautiful chun/tenmoku combo?
2. How thin are your glazes to get them to layer without cracking and falling off while drying?
3. Do you fully dip in tenmoku then fully dip in chun?
Thanks for the help and the inspiration.
Kind regards, Sarah


Hi Sarah,

Lovely to hear from you, thanks for your kind words, & welcome to my site.

Sorry that it has been a couple of days replying to your comment, the whole Blog system went down and it was impossible for me to post a comment. I also notice that your comment got removed in Blogger's world wide hiccup, but I fortunately had already grabbed a copy before it vanished so have included it above my reply!

You don't say if you are in New Zealand or in another part of the world, so I am not sure if you are able to access the same clay as me, but.. I have been mostly using Southstone, which is made by Southern Clays Ltd in Dunedin NZ. Southstone is a rather sandy, open clay, and is a bit problematic in an electric kiln as it needs a lot of heat to vitrify. I use it, because it is my local clay and I like to support Southern Clays as much as I can. One trick that I do with it that will lower its maturing temperature, is to wedge in a little earthenware clay (Southern Clays Brick Red works nicely). I find that 4 parts Southstone to one part Brick Red gives me something that will be mature at cone 9 or 10, and it also has a better colour in an oxidized firing.

Southstone does contain a bit of iron oxide, and this is helpful when trying chun glazes. It is far harder to get chun glazes working on a white stoneware body. Having said that..., it is possible. I have tried the tenmoko/chun combination over a white slip, and this can work, but an clay that has some iron is an easier starting point.

I put on my glazes as thickly as I can for the chun/tenmoko combo. They do tend to crack as they dry, and I give them a gentle rub with my fingers to "heal" them over. Occasionally the glaze may crack and lift. I carefully moisten the lifted edge with a little water applied with a small paint brush, then push it down again.

I do often dip the tenmoko glaze (but have been known to pour it or brush it). I mostly pour the chun glaze for the inside of a bowl, swirl it around, and tip it out again. Brushing is impossible with that glaze. I quite like the glaze to be uneven, so I have never sprayed it, but I imagine that this would work OK.

Hope that is of some help. It is difficult to talk about glaze thickness and so on, as it really is something that you need to experiment with with your clay and glazes... there are so many variables. I should add that I bisque to 1000 Centigrade (Southern Clays suggests 1050 C), as I quite like my bisque to be reasonably absorbent. Do keep in touch and feel free to ask questions.

Best Wishes,
Peter

Anonymous said...

Hello, just wondering if this beautiful glaze is food safe?

Peter said...

Hello Anonymous,
Thank you for your question. I have never had this glaze tested, but I am confident that it is safe. The materials used are all none toxic apart for the 6 percent Zinc Oxide. I doubt very much if the Zinc would leach out as this is a nice, vitrified, mature glaze.
Best Wishes, Peter.

jean szostek said...

hi peter there is no recipe for the clear glaze that i think is also important i presume?
jean from belgium

Peter said...

Hi Jean,
The blue chun effect is best achieved by using two glazes, an almost clear one over one that is very dark.

The "clear glaze" part of the chun is as follows:
Potash Feldspar 46
Dolomite 6
Zinc Oxide 6
Whiting 10
China Clay 2
Silica 30
(I usually add 1-2 percent bentonite to this to make it easier to apply).

This glaze is put over an iron bearing glaze and will form a blue chun effect if put over an iron bearing glaze or slip. On its own it is a slightly milky to clear glaze, becoming more clear towards cone 9.

A suitable iron bearing glaze would be:
Silica 41
Potash Feldspar 34
Whiting 16
China Clay 9
Black Iron Oxide 10
Many other glazes with about this level of red or black iron oxide will do just as well, it is worth experimenting.

The combination of glazes that I have given you here work for me between about cone 9 and cone 11.

Whilst I have mostly found this a very reliable glaze combination, I have had some problems with it recently after I purchased a finer ground zinc oxide, I suspect this is too effective as a flux. I am still working through this.

Hope the information helps. Good luck! P

Anonymous said...

On your first post (the one where you said you needed to catch a bus) you mentioned that you used three glazes, with the middle glaze being a clear glaze with rutile and copper. However, you make no further mention of this glaze in the later post. Am I correct in assuming that this glaze is unnecessary?

Peter said...

Hi Anonymous,
Thank you for your question, I would like to be able to help, but I am struggling to find the blog post that you refer to (where I refer to needing to catch a bus), could you give me the date of the post, and then I can help you more regarding the glaze question. P.

Peter said...

Hi Alex,
Really sorry for the muddle about the glaze. Here it is. This cone 9 glaze is really a Janet DeBoos one, number 144 from her book "Glazes for Australian Potters".
I never found the original recipe much good, it did not yield the "smooth, white glaze" that she described, and it often seemed to craze on the clay I used. At some stage I tried it as a base and added other things, then found it very useful.

Her glaze is as follows:
Potash Feldspar 40
Silica 200 25
Calcite 15
Ball Clay 10
Zinc Oxide (dense) 5

To this I add Bentonite 2
Copper Carbonate 1
Rutile 3

In an electric kiln, this will probably give you a green, but it can also give a lovely variety of blues right through to a deep blue/purple in reduction. The glaze is quite like a chun in effect, and I will sometimes use it along with a chun glaze for variety, under, or over the chun glaze. I apply it in an informal, spontaneous way. It is useful for this, both in oxidized or reduced firings.
(I have also posted this comment on the chun glaze post).
Good luck with your own experiments with these glazes.

Alex said...

So to recap, the beautiful blue bowls at http://opopots.blogspot.com/2009/03/chun-glaze.html have three layers; a tenmoku underglaze, a layer of the transparent you just mentioned on top of that, and a layer of the chun glaze on top of that, correct? Is the middle glaze necessary to give those beautiful blues? Thanks for the speedy responses.

Peter said...

Hi Alex,
The "middle glaze" (the DeBoos 144) isn't strictly necessary for the blues, but can make them more interesting. I think that your three layer description is probably a bit too "formal".. Yes, the tenmoku goes first, but what is done over that is more instinctive. I suspect that, in the case of the blue bowl on this post, the next glaze to be applied would have been the chun, and the adapted DeBoos added by pouring in and out quickly, more as a splash then as a complete coat. Hope all that makes sense!

Really it is the sort of thing that is hard to describe as a "method", as I mostly end up in a state of creative chaos when I am glazing, surrounded by a growing number containers of glaze, and am inclined to splash in a bit of this and that, as the "spirit moves"!

Alex said...

Thanks for all the help!
I'l definitely be playing around with this glaze, I'm going to try mike's suggestion of .25 lith carb and 10 custer feldspar for cone 6 oxidation firing. I'll keep you posted on how it goes.

Sumi @ Carol Jones Writing Center said...

Obviously I just need to test this, but what are your thoughts on trying for the blue chun on a heavy iron dark clay body? My thoughts are that it would work just like a slip or glaze would to bring out the blue...maybe? However, I too am firing at cone 6...did that potter ever get back to you about the alterations she made for the success?

Peter said...

Hi Sumi,
The heavy iron dark clay body would be ideal. Chun blues are much easier to do with a dark background. I think that the theory is that the dark background absorbs the other colours of the spectrum, but the chun reflects back blue light to the viewer. Without the dark background, the other colours of the spectrum reflect back, and you lose the blue chun effect. Definitely test, and re test... Sadly, the other potter hasn't got back to me. It would be very interesting to see photos of work that has been done at cone 6 with an adaptation of this glaze.

Alexa said...

Hey Peter,
I am trying to make an underglaze for some chun glazes and was wondering if you had a recipe for an underglaze at cone 10?

Peter said...

Hi Alexa,
You can use chun over all all sorts of other glazes and it is well worth experimenting, for example... I have used them over copper reds, and shino.

However, you will usually get a good result over a tenmoko (temmoko) style glaze, as a really dark, almost black, glaze will absorb the unwanted light spectrum, and leave your chun glaze to reflect back to you the blue wavelengths.. thus you should see a nice optical blue colour if all works according to plan!

This cone 10 glaze works well as an underglaze for chun, and you should find it a good one to start with:

Silica 41
Potash Feldspar 34
Whiting 16
China Clay 9
Black Iron Oxide 10

Note... If you under fire a chun glaze, you will usually end up with a milky white; and if you over fire a chun glaze you will end up with a clear glaze that just shows the dark under glaze without giving you blue.

Best Wishes, P