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Very few glazes – in my opinion – have not been made by someone somewhere before me.  I’m not talking about specific recipes, but instead the look of a glaze which can be accomplished by multiple formulae.  This is especially true of all the lovely glaze types made by Chinese and Japanese potters over the centuries.  More often than not, if you develop a glaze – especially an iron containing glaze – it has a precedent elsewhere.  Add to this the fact that I’m a stickler for accuracy, and you get the article I am about to write. 

It happened like this.  I start messing around with glaze recipes and test firing things, and Robert off-handedly says something like, “Oh, that’s a Kaki glaze,” and I have to know if that’s right.  The last thing I want is for someone to think we’re idiots because we don’t even know what to call our glazes.  Now, I could get around this (and have in some cases) by giving our glazes unique names a la “Midnight Peacock”.  If you come up with it, you can name it anything you like.  However, I have started to feel more connected to the history of pottery.  This is an old – really old – craft and we are continuing a very respectable tradition.  So, if I happen to generate, de novo, a glaze recipe that when fired, looks very much like something ancient, I would like to give it a name which reflects that. 

So, there are lots of iron-containing glazes that range from pale green (celadon) to black (tenmoku).  In this article, I won’t talk about celadon as this requires a reduction atmosphere – which I don’t do; so, I don’t feel qualified to talk about them.  I also won’t talk about amber glazes which I haven’t done a lot of work on up to this point.  Most of what I have been working with lately includes iron-containing glazes where the iron (both red and black) is 8-15% of dry weight.  I’ve done a decent amount of research into what different looking iron glazes should be called with respect to history.  That research is summarized here as “iron glaze taxonomy” and includes the following types: Kaki, Ohata Kaki, Teesha, Tenmoku, Hare’s Fur, Oil Spot, Tea Dust, Partridge Feather, and Tortoiseshell.  I have to say that a lot of these glazes seem to have been popularized-revitalized-westernized though the legendary collaboration between Hamada Shoji and Bernard Leach. 

NB – Sometimes, it seems a name refers to a glaze as well as a form.  I have noted these redundancies where applicable.

Kaki (Persimmon)

  • Emily’s Description: A saturated iron glaze that is brick red with black speckles the density of which changes depending on how thickly the glaze is applied.  I like the metallic black speckles and tend to apply my Persimmon on the thicker side as in the photo below.
Notice how the density of black flecks increases with increasing thickness of the glaze.

Notice how the density of black flecks increases with increasing thickness of the glaze.

  • Real Definition(s) from Multiple Sources:
    • A feldspathic glaze containing liberal amounts of iron which crystallizes during cooling.  This glaze originated in Mashiko, Japan and utilizes local rock. 
    • According to Shoji Hamada a kaki glaze has the color that a persimmon is on October 24.  ***NB: I am not sure what a persimmon looks like on Oct 24, but from looking at pictures of persimmons, this glaze looks more like a dried persimmon (brick red) than a fresh one (orange).  Go to Wiki http://en.wikipedia.org/wiki/Persimmon for pictures of fresh and dried persimmons.
    • A glaze requiring reduction atmosphere during cooling.  ***NB: I do not utilize reduction in my kiln for my “Persimmon” glaze (or any other).  Additionally, Bernard Leach mentions in A Potter’s Book that the color is due to oxidized iron crystals.  I tend to agree with this definition.
    • Kaki-no-heta – Best I can tell, this is a rust iron colored glaze used on chawan (tea bowls) first made in Korea that were imported into Japan.  I have more to say about this under Ohata, below.
    • Simply, kaki is Japanese for persimmon.
    • Kaki can also refer to the shape of a particular flower vase.
Tenmoku

  • Emily’s Description:  A high-iron, feldspathic glaze that has more flux than the other high-iron glazes covered here (traditionally due to wood ash, but in contemporary recipes flux can be from other sources).  Tenmoku glazes can have different surface textures.  Mine is a Honan style as shown in the photo below.  

 

I am very proud of my Honan style tenmoku. It's a glossy deep black over the body that breaks to rust red on the edges. Also, where it pools, grey-green crystals have formed (base of handle).

I am very proud of my Honan style tenmoku. It's a glossy deep black over the body that breaks to rust red on the edges. Also, where it pools, grey-green crystals have formed (base of handle).

Tessha

  • Emily’s Description: A saturated iron glaze which is predominantly rust red but exhibits areas of metallic sheen.  My Ohata Kaki Red came out of the kiln with a silvery-purple sheen on one side (kiln wall side) as shown in the picture below.
On the kiln wall side of this mug, the Ohata Red has acquired a metallic purple sheen indicative of Tessha. This illustrates how critical cooling rate is to the formation of crystals for some of these iron glazes.

On the kiln wall side of this mug, the Ohata Red has acquired a metallic purple sheen indicative of Tessha. This illustrates how critical cooling rate is to the formation of crystals for some of these iron glazes.

  • Real Definition(s) from Multiple Sources:
    • A Japanese glaze with purple-red or silvery areas due to the oxidation of iron crystals formed upon slow cooling, often mottled with patches of brown or black – similar to kaki. 
    • Specifically, tessha refers to an iron-rich alluvium which is used in under painting or as a colorant in glazes.  Thus, it can also refer to the glaze of which it is a constituent, tessha-yu or iron sand glaze.
Tea Dust

  • Emily’s Description: A high-iron glaze that has predominant green markings sometimes on a grey-black or very dark brown background, usually satin to matte finish.  According to John Britt, these require some magnesium which contributes to the formation of the characteristic green crystals.  I actually don’t have a tea dust glaze at this time.  I was working on one, but got sidetracked.  There are some fantastic picture links below.
  • Real Definition(s) from Multiple Sources:
    • Tea Dust is an iron crystal glaze ranging from green to yellow that requires a reduction atmosphere.  It originated in China during the Song dynasty and continued to be tweaked through the reign of Qianlong.

http://www.cicadaasianart.com/gallery/Category/2/Item/226/Photos/

http://www.teadust.com/gallery/mo/mo_da_586.htm

http://s0.artquid.fr/art/0/87/22466.285483480.1.o189116784.jpg

Ohata

  • Emily’s Description: A brick red iron containing glaze with little mottling.
I distinguish Ohata Kaki from typical kaki (persimmon) by the lack of mottling.

I distinguish Ohata Kaki from typical kaki (persimmon) by the lack of mottling.

  • Real Definition(s) from Multiple Sources:
    • I cannot find an original definition or historical reference to “Ohata” glazes or “Ohata Kaki” glazes.  Lots of contemporary potters use “Ohata Red” glazes, but I can’t find any information with more substance.  There is an Ohata, Japan, and they have traditionally made pottery there.  However, it does not seem to be overwhelmingly rust-red.  Neither can I find references to a potter named Ohata who may have come up with an iron red glaze, nor a family who might have sponsored such a potter.  I found one reference in a conversation thread (http://groups.google.com/group/ClayCraft/browse_thread/thread/60c55f12d9cc2c67) where someone mentioned that Ohata was someone’s name (as I suspected) and that what we call “Ohata Kaki” would not be recognized in Japan as it is not a traditional Japanese glaze (unlike shino or tenmoku).  The consensus seemed to be that a Japanese potter might call a piece glazed in ohata kaki simply kaki. 
    • So, this takes me back to the beginning with one of the names for Persimmon, kaki-no-heta (translation: persimmon calyx, persimmon stem, navel of the persimmon).  Is this too simple?  Is it possible that kaki-no-heta at some time became transliterated into kaki ohata?  Ohata glazes seem to be persimmons without as much black speckle.  They are certainly very similar in composition.  Anyone who has further information on this or any aspect of my article, please feel free to comment. 
REFERENCES