Blue Celadon Glazes

Blue Celadon Glazes
19/01/2015 Derek

All of the following Blue Celadon recipes and more can now be found on my new open-source ceramics recipes website, Glazy:  http://glazy.org/search?category=36&subcategory=41

Complete Guide to High-Fire Glazes

These are tests of some of the Blue Celadon Recipes found in High Fire Glazes.  Tests fired in multiple kilns in temperatures ranging from 1300-1310 Celsius reduction.

Craig Martell Blue Celadon

Custer Feldspar:  61.7

Silica: 21.2

Barium Carbonate: 4.5

Wollastonite: 12.7

Black Iron Oxide: 1

Pete Pinnell Blue Celadon

Custer Feldspar:  24.5

Silica: 34.3

Whiting: 19.6

Kaolin (Grolleg): 19.6

Barium Carbonate: 1.9

Tin Oxide: 1

Yellow Iron Oxide: 0.5

Sam's Satin

Custer Feldspar:  40

Silica: 34.5

Whiting: 15.5

Barium Carbonate: 4

Dolomite: 6

Yellow Iron Oxide: 0.5

Cliff Lee Blue Celadon

Custer Feldspar:  50.5

Silica: 24.9

Whiting: 17.2

Kaolin (Grolleg): 3.7

Dolomite: 2.6

Zinc Oxide: 1.1

Red Iron Oxide: 0.75

Choy Blue

Custer Feldspar:  50

Silica: 28

Whiting: 6

Kaolin (Grolleg): 4

Barium Carbonate: 12

Red Iron Oxide: 2

Ishii Blue Celadon

Custer Feldspar:  49

Silica: 31

Whiting: 20

Black Iron Oxide: 1

Celadon Blues

Robert Tichane’s Celadon Blues focuses primarily on Chun (Jun) glaze, but also covers Qingbai, Longquan, and other ancient Chinese glazes.  While perhaps not as informed as Nigel Wood’s Chinese Glazes, Tichane approaches the subject from the perspective of a glaze chemist and gains valuable insight into the nature of blue celadons.  Through testing, Tichane arrives at two formulas.  The “532.1” formula contains 50 parts feldspar, 30 parts silica, 20 parts limestone, and 1 part iron oxide.  The “5321.1” formula is the same but adds 10 parts kaolin.  The type of kaolin added greatly affects the color of the glaze, for blue celadons a kaolin very low in titania such as Grolleg or New Zealand Halloysite is required.

Below on the left is Tichane’s 532.1 formula with 1% yellow iron oxide (YIO).  On the right is the same formula but with Wollastonite instead of Whiting (of course this adds some silica to the mix).  These tests were fired in a public kiln, temperature is uncertain but at least Orton cone 12, I believe Tichane’s tests were fired to cone 10.

Porcelain, Orton Cone 12 Reduction

Porcelain, Orton Cone 12 Reduction

It is quite simple to create a blue celadon suited to your particular firing style using Tichane’s methods and triaxial blends.  From a triaxial blend of potash feldspar, silica, and whiting I arrived at a recipe suitable for Orton cone 11-12 reduction firings:  56 feldspar, 30 silica, 14 whiting plus .6-.8 yellow iron oxide.  Some variants of this glaze are shown below.  All tests fired to approximately Orton cone 12 in heavy reduction.

.6 YIO

.6 YIO +2 BaCO3

.6 YIO +2 BaCO3 +1 SnO2

.8 YIO +2 BaCO3 +1 SnO2

.8 YIO +2 BaCO3 +1 SnO2 +2.5 Dolomite

Formulating Your Own Celadon

Personally, I really like the Pinnell Blue Celadon recipe in John Britt’s book.  It’s a very beautiful, smooth and “natural-looking” blue celadon.  However, I’ve found that the glaze is difficult to apply given the large amount of Kaolin in the recipe.  A few months ago I fired about 20 pieces with Pinnell celadon with beautiful results except that the glaze crawled on every single pot.  I still haven’t determined if the problem was due to a) glaze application (sprayed inside, dried, then sprayed outside), b) ball milling the glaze for too long (3 1/2 hours), or c) too much shrinkage of the glaze due to the kaolin (using New Zealand Halloysite).

And although no-kaolin recipes like Tichane’s 532.1 and Craig Martell’s blue celadon almost always fire a nice blue, they seem a little artificial to my tastes, perhaps a little too colorful.  It’s also because this type of Wollastonite-based celadon is covering a lot of Jingdezhen ware these days, and I’m tired of seeing it.  Finally, these glazes tend to sink to the bottom of glaze buckets and solidify there due to lack of clay.

So I decided to do a simple triaxial, based in part on Tichane’s 5321.1 recipe.  I still want kaolin in the recipe, but not as much as in Pinnell blue celadon, so I picked an amount halfway in-between the two, 10%.  (Again, I’m using New Zealand Halloysite.  Grolleg is also suitable.)  I also decided to add 3% dolomite- based on Nigel Wood’s Chinese Glazes and past experience I know that a little magnesium combined with the calcium can give the surface a slightly waxy feel.  With 13% of the recipe taken up by kaolin and dolomite, I have to adjust 87% Potash Feldspar, Silica, and Wollastonite.  (You could use Whiting of course, although it out-gasses more than Wollastonite.)  Finally, I’m not adding any Barium Carbonate.  (If you want a rich blue celadon you can try adding 2-4% Barium Carbonate.)

All these tests are the same porcelain body fired together in a heavy reduction atmosphere to Orton cone 10 1/2.

I realize it’s really difficult to see the differences between glazes in such a small photo.  Furthermore, some tests look richer, but it’s partly due to small changes in camera exposure and glaze thickness rather than glaze composition.  I prefer the diagonal lines going down with Wollastonite at 20-22 percent.  I should have added another couple rows to the bottom of the triaxial, because I prefer the glazes more as the silica increases.  (I thought there was already too much silica in the glaze, including silica contributed by the wollastonite, so I stopped early.)

Below is a bigger photo of one of the tiles.  It’s almost like some Longquan glazes I have seen.  I think this particular glaze would look great over carving or molded/sculpted work, and it might really look good on stoneware or dirty porcelain.  I’ll post pictures once I try it out.

I’ve posted the recipe on Glazy:  http://glazy.org/recipes/3189

Adjusting Pete Pinnell's Blue Celadon

Years ago I tested Pete Pinnell’s Blue Celadon recipe and loved it, so much so that I didn’t even think of bothering to adjust the original recipe to suit my materials.  But this last kiln I wanted to try swapping out Whiting for Wollastonite, and I thought I might as well adjust for New Zealand Halloysite instead of Grolleg.

Below is a small triaxial of Pinnell’s Blue Celadon adjusted for New Zealand Halloysite.  The top of the triaxial is the closest verison to the original.

Using Halloysite instead of Grolleg wasn’t a huge change, and I couldn’t see much of a difference from the original recipe.  The bottom of the triaxial is somewhat interesting- color improves as silica replaces halloysite.  This is a similar finding as with Tichane.

Replacing Whiting with Wollastonite

Next is Pinnell’s Blue Celadon with New Zealand Halloysite instead of Grolleg, and Wollastonite instead of Whiting.

The recipe at the top of the triaxial most closely matches the original recipe.  As with the previous triaxial, color is better on the right side where silica is greatest.

As with many wollastonite-based celadon glazes, this glaze has a very fine network of bubbles that are smaller and more evenly sized than those in the whiting recipe.

It is difficult to see in the photograph, but the color is also better in the wollastonite version.  I believe this is due in part to the fact that much of the silica is introduced with the wollastonite.

 

 

My favorite glaze is the Halloysite/Wollastonite recipe at the top of this triaxial (which is closest to the original recipe).  You can find it on Glazy: http://glazy.org/recipes/4571

However, I also like the glaze on the right of the second row.  I wish I’d done a test to the right of the top glaze, in other words Potash 30.5, NZ Kaolin 18.5, Silica 24.

Pinnell's Blue Celadon with Halloysite and Wollastonite.