Tuesday, January 28, 2014

Ahhhhh Tenmoko, (Temmoko) and the art crazing, bubbling, and crawling!

Some of the nicest things in life are also some of the naughtiest, and this is also true of ceramic glazes! Yes, if you want hygienic craze free, non- toxic, dishwasher proof oven ware, you will probably go for a clear, shiny, thin, faultless, sprayed-on boring coating that is best produced in a ceramics factory... Yawn!

Many of the more interesting glazes are also very practical, a good Tenmoko glaze will generally fit well, are likely to be non-toxic, and they look great with food. Sadly, they are not the height of fashion these days, but in the 1960s you probably weren't a potter if you didn't have a good Tenmoko glaze to slosh over your mugs, bowls, teapots, and casseroles.

Ahh, Tenmoko...! But it is "brown" you say, as if "brown" were a disease! Ha! Just imagine a bowl this colour brimming full of pumpkin soup! Or with a green salad with some tomatoes! Or tumbling full of oranges! Actually this tenmoko bowl would be a bit large for soup, it is nearly 12 inches in diameter and stands 3 inches tall (300mm x 75mm). I got this out of the kiln about 3 days ago, and was amazed at the colour that is in it when you tilt the bowl around in the sunshine. Sadly the rusty flashes of light off iron crystals, and pinpoints of violet-blue don't show up in a photo, but it was a joy to behold.

The glaze is one I usually refer to as "BTM" (Black Tenmoko) in my high fired glaze page. The glaze was passed onto me by my friend, Peter Watson. And it may be a Dartington Hall recipe.

I have put the recipe in my High Fire Glazes page, and I often "tweak" it to suit my firing temperature.

I was firing to cone 10 (almost 1280 Celsius in my electric kiln) and this time round I used;

Nepheline Syenite 55
Talc 15
Wollastonite 15
Ball Clay 15
Silica 15

and red iron oxide 8.

You can also use Potash Feldspar instead of Nepheline Syenite, and China Clay instead of Ball Clay. This will raise the maturing temperature a cone or so.

Here is a bowl with a nice pool of thick crazed and bubbly glaze. The bowl is just over 11 inches wide by 2 inches high (280mm x 50mm). I used the same glaze combination in a firing that I did a couple of days before this one. There are two alkaline glazes, both chemically the same, but using slightly different ingredients. The glaze that I use in the middle has calcium carbonate as a flux, and I find it gives me a bluer glaze where it is thick, but can cause problems with bubbles which are not nice when they occur around the rims of bowls, but can be rather splendid in the centre of a decorative bowl. The glaze that I used around the rim and sides of the bowl uses Wollastonite to provide the necessary calcium. Wollastonite is calcium silicate, and it doesn't release bubbles of carbon dioxide, whilst the glaze is firing, where as calcium carbonate does. The two used together like this are rather nice I think. You can find the recipes for both these green glazes on my High Fire Glazes page.

And, finally, crawling...

I am doing some tests of a glaze that I have formulated to have abnormally high shrinkage whilst it fires. I am testing this glaze over various other glazes, and some rather interesting results are starting to emerge!

Here are some tests that I did some time ago. These were 50/50 mixes of Nepheline Syenite and Magnesium carbonate over an iron red glaze. I have written about that on my High Fire Glazes page.

I must head off to my studio to glaze some more pots!
The sun is out today..... Amazing to see it after lots, and lots, and lots, of rain!


gz said...

We've had 50% more rain than usual....gets a bit wearing....that, and ice!!

Arkansas Patti said...

Brown is a favorite color and you are right. A salad would look stunning in that bowl.
Could you send some of your rain our way. We are getting critical here.

cookingwithgas said...

I know I am old school, but I can fall head our heels for a good temmoko. That warm breaking black to brown.....love...

Linda Starr said...

In the workshop I just took with Akira Satake he used a tenmoku inside some of his mugs and tumblers and the contrast with his unglazed exterior surfaces looked wonderful. In college we had a tenmoku which broke to a reddish brown which I loved. those two bowls with crawly glazes look super.

Armelle Léon said...

Wonderful glazes Peter, and the sun is a plus. I finally manage tp post some season greetings cards to my friends and they are reaching NZ, probably in February...

Pat - Arkansas said...

Love the brown! And.. that bowl is just about the right size for MY serving of soup!

I love the "crawling" glazes!

Peter said...

Thank you everyone for your comments, I'm sorry to be slow to reply... I did reply a yesterday, or I thought I had, but my comment appears not to have "stuck" for some reason! The marvels of technology!

Hi Gwynneth,
It is possible to forget what the sun looks like when it rains so often... glad that we don't have ice as well!

Hi Patti,
A nice dark brown bowl does look good with food, it is a bit like a flower garden. Sad that you are struggling with lack of rain, I think we should send some your way... I'll see what we can arrange!!! :)

Hi Meredith,
Falling "head over heels", glad that tenmoko and romance go together!

Hi Linda,
The red brown Tenmokos are lovely. I have a recipe that can sometimes give quite a nice rust colour where it is very thin. It seems a bit "picky" as to what clay it is over. On some it just gives brown rather than rust.

Bonjour Armelle,
Sunshine..., it is a rare and wonderful thing!! Well done getting greeting cards sent..., I still haven't managed that yet. Maybe my ones will have to be mid year celebration cards or something!!

Good Morning Pat,
I see that you have a good, healthy appetite for soup! I must say that it can be just the thing on a winter's day, with some nice crusty home made bread (or some toasted shop bought white bread!)... Crawling glazes are really interesting I think, and more experiments will be conducted very soon with them.

Sue said...

Hi Peter and Laura,

Its good to see you so busy and so enthused with all the glazes.
It must be a great feeling to be fit and well enough to carry on with your work/play.


Peter said...

Hi Sue,
Good to hear from you. It is nice to be doing some creative things again.

Hiltonsister said...

I too love tenmoko and have a collection of pieces mostly found in charity shops and recycling depots. Often dusty when I find them it's like magic to see them emerge subtle and shiny. Started repairs with gold years before finding out it was an art-form in Japan. Now it's a joy to find a damaged one!

Peter said...

Hi Hiltonsister,
Welcome to my blog and thank you for your comment. I am delighted to read that you have discovered the magic of tenmoko glazes and that you go to the trouble of repairing broken pieces with gold! It is a lovely thing to do, and it gives the damaged work a new life as something to be treasured.